“The main odour problems at Mogden STW are associated with digester operations. Further problems are caused by regular use of the storm tanks for balancing dry weather flow and insufficient cleaning of these tanks after emptying. A general septic odour is associated with the east-side works caused either by odorous substances from the incoming trade wastes or by septicity problems in the rising main. Odour problems at the inlet to the west-side works may be caused by the return of supernatant liquor from Perry Oaks sludge treatment works.”
“The major source of odour at Mogden Sewage Treatment Works is digester gas escaping into the atmosphere in the anaerobic digester area. Elimination of digester gas emissions would greatly reduce the overall odour problem at Mogden. It is recommended that the Mogden anaerobic digesters be sealed to prevent escapes of digester gas, either using flexible seals between the fixed wall and floating roof or the conversion of the tanks to fixed roof digesters. Satisfactory technology for the implementation of flexible seals on the existing floating roof digesters is not available but it may be possible to develop suitable sealing methods. If this is not possible, replacement by fixed-roof digesters may be required. As an interim measure, ferrous chloride dosing of the sludge prior to digestion is recommended to reduce the H 2S content of the digester gas and hence odour emissions. ... East side storm tank use during dry weather flow should be reduced to a minimum and improvements implemented for tank cleaning, removal of solids from the tank bases prior to storm water emptying, for example. Intense aeration of the inlet flows to both the east and west works may be possible to strip out odorous substances, hence reducing odour emissions over the entire works. The aeration air would require treatment by odour biofilter or bioscrubber. The common interest research programme U0703 will report the results of aeration trials in March 1991.”
“The regular use of the storm tanks, even during spells of dry weather, to balance excess sewage flow produces a significant odour along the east side of the works. Sewage from the rising main inlet to the east side works contains odorous substances, this is shown by the H 2S levels of over 20ppb around the inlet and over 75ppb within the screen house. Use of the storm tanks to balance this flow provides a large surface area for odour emission. Although the H 2S concentrations are low in comparison to the emissions from the digester, 10-20 ppb compared with values of over 400 ppb, the rate of emission owing to the large surface area is high and dispersion of the odours offsite occurs. It is recommended that the use of the storm tanks in minimised, especially during periods of warm, dry weather when the sewage is concentrated. If the use of tanks cannot be eliminated, the retention time of the sewage in the tanks should be reduced. Additional odour problems would be caused if solids remaining in the storm tanks are exposed during emptying. It is recommended that the sludge and debris be scraped out whilst still under supernatant cover.”
“Work carried out by R. Krishnan, Research and Development, in October 1992, identified a very large source of odour emitting from the wet well ventilation stack in the North end of the site. This was attributed to the return of liquors from the thickening plant. In fact the stack was found to be the largest single potential source of odour found at Mogden STW.”
“However, it is considered that the digesters are no longer the major source of odour. We have installed 2 different odour control devices in the digester area: “Lute” seals, where the dome sits on a water seal, as opposed to a sludge seal, have been fitted on two digesters. A third digester has a rubber seal fitted around the annulus of the dome. Current gas flow problems from the digesters to the Powerhouse are being addressed by an Engineering capital scheme. The occurrence of inconsistent bell heights is thought to be due to these problems, as well as to the weight differences between newly refurbished bells, and the older, more corroded ones. We will continue to investigate all options: if the gas flow problems can be resolved, allowing us to minimise the bell heights of the digesters, then further odour control of individual digesters may not be necessary. Refurbishment of the digesters will continue, on a rolling programme, until 1998.”
“Where measurement of H 2S concentrations are thought not to be a reliable guide to the spread of odour then an alternative measure of odour concentration may be made using olfactometric analysis. A number of protocols exist for carrying out this type of analysis, but are based in using a panel of human “sniffers” to determine the number of times that a sample must be diluted to reach the threshold for detection.”
“Progressive deterioration of the Mogden digestion process over many years, coupled with increased works loadings and greater sludge make has put pressure on the entire process such that digestion detention periods and temperatures achieved are insufficient to give complete stabilisation of the sludge. Whilst Perry Oaks operated as a lagooned/air drying process this deficiency was masked: since installation of centrifuges to accelerate clearance of the site the underlying problem has manifested itself in odour generation. Recent installation of gravity sludge thickeners has been unsuccessful due to the presence of co-settled surplus activated sludge - a process constraint now fully recognised. The urgent need is to remove a substantial portion of the SAS from the gravity thickener stream and to provide an effective but temporary alternative to allow evaluation of performance, an immediate improvement on the digester feed sludge thickness and consequent reduction in odour problems.”
“Since the funding is within the AMP II ‘K’ deal any savings made on the cost of this project are in the interests of Thames Water and it is planned to seek and evaluate novel and innovative options to the conventional design, with the intention of reducing the capital costs.”
“3.1 The Asset Strategy for Sewage Treatment indicates that the obligations mentioned as a requirement of the UWWTD must be met by31 December 2000 and the obligations are funded under the AMP II ‘K’ deal. Recent investigations carried out during asset plan development have indicated that Mogden’s overloaded treatment plant could not cope at present with an increase in flow to full treatment of some 23%. Storm tank capacity is 15% below that required. The West side inlet works does not provide screenings removal.”
“...the Table below indicates the number of FSTs required if 30m diameter tanks are used instead of 18m. Again, in all cases a MLSS of 300ml/g has been used for calculations and 23 FSTs for the existing West Side plant. As shown below the number of FSTs can be greatly reduced using the larger tank. Subsequently, I would imagine that the Capital cost can be reduced further. This in turn would favour the conventional and Chemical Dosing Options against the Nitrifying option when NPVs are considered.”
“The SSVI at Mogden generally runs between 40-60 ml/g. Therefore designing to 80ml/g would not be considered risky. If we designed the extension on an SSVI of 80 ml/g and for whatever reasons the SSVI increased to 100ml/g (i.e. as a consequence of insufficient air caused by an air blow, shock load etc) the maximum flow to the FST’s will be reduced as indicated in Table 2. ... The number of additional FSTs is identical for both the Conventional extension and the Chemical Dosing options. In the case of the nitrifying plant no additional FSTs are required unless we design for an extension of 450 TCMD and using an SSVI of 120ml/g, in which case 3 FSTs are required.”
“This project provided for urgently needed sludge thickening trial at Mogden STW in order to confirm the preferred treatment process to improve digestion and control odour problems...”
“Recent installation of gravity sludge thickeners has been unsuccessful due to the presence of co-settled surplus activated sludge - a process constraint now fully recognised. The urgent need was to remove a substantial portion of the SAS from the gravity thickener stream and to provide an effective but temporary alternative to allow evaluation of performance, an immediate improvement in the digester feed sludge thickness and consequent reduction in odour problems.”
“At CTS the proposed scope consisted of the purchase and installation of a single Belt Thickener in an existing building and included for the minimum levels of support works to ensure safe and effective operation on a manual-only basis.”
“BOD removal rate across the PSTs is historically found to be between 35-45%. The trial indicated that at high loading rates of 35m 3/m 2/d, a BOD removal rate of 60% could be achieved. This used Ferric Chloride (14.5%) at a dose rate of 50 ppm as product and the Polymer Magnafloc 1011 at a dose of 0.06 ppm. Greater BOD removal rates of up to 78% were attained at lower hydraulic loading rates.”
“a) the effect on sludge pumping for both raw and digested sludges; b) the increased production of raw sludge; c) changes in sludge rheology/properties particularly for digested sludge to Perry Oaks and the likely effects on our current proposals for dewatering at Iver South/recycling to land and possible fallback of incineration at Mogden STW. d) the effect on digesters.”
“A new storm screening installation to be provided to the east side inlet works area. The west side plant to be provided with a new inlet works with 6mm screening and grit separation. A new west side works extension, including primary, aeration and final tanks. A chemical dosing system will be installed to the extended west side plant. A second belt thickener and associated polymer plant to reinforce the SAS treatment stream and provide for the additional sludges generated by other process changes. A range of minor H&S and integrity items as identified. Enhanced ICA/SCADA as necessary to maintain effective works control of the plant in its more severe operating conditions. Replacement final tank diffuser drums deferred from project 4LRB for further trials.”
“Odour Control. There is a peat bed for the RSHT, two bioscrubbers for the PFTs and one bioscrubber for the TSHTs. All of these require attention. The peat bed is overdue for renewal ... One key thing Alan [Crump] and I discussed was the potential for upsetting the PFT operation due [to] Odour problems, blocked drains and failing supernatant [Pumping Station]. Quite often because of one of these problems we can quickly deteriorate into a vicious cycle and recovery of the PFTs can prove an almost impossible task. It was only really the recent heavy rainfall that enables us to recover their operation after a poor few months.”
“Bioscrubber serving the TSHT The GRP covers to the TSHTs were in average condition, three hatches had damaged hasps, one hatchway was badly damaged and left open due to the presence of a temporary bauer delivery pipe. In total the damage was enough to compromise odour capture. The Bioscrubber was in average condition, wash water was being displaced to drain at an appropriate flow rate unfortunately neither the fan or the pump was running at the time of the visit so I cannot comment on performance. The washwater connection was noted as temporary in the form of an unsupported lagged pipe descending down from the digester area. Recommendations: Make good the hatchways on the TSHTs. Remove the temporary Bauer connections. Operate the bioscrubber. Provide standby pump and fansets. Bioscrubbers serving the PFTs and Liquor pumping station The initial appearance of the units is very poor this is largely due to ponding of sewage effluent around the units from a leaking flange on the main body of one unit. The local flooded area has accelerated the corrosion of the cable trays and supports in the area. Both units had fans running but one unit showed no flow apparently due to a broken fan drive belt. The adjacent unit showed a really low shaft speed on the fan, the motor had been replaced with a unit 50% smaller (in physical dimension). Make up water was found to be running full bore to drain, although this does not present a process problem to the bioscrubbers it is clearly an unnecessary demand on the new washwater station. The ductwork was in poor condition with some taped joints and a clearly asymmetrical system without balancing dampers between the PFTs. The connection to the supernatant pumping station was via a partly buried 100mm duct at the extremity to the distribution system, it was evident from the gross corrosion of traywork above the station that this line does not give containment of odour. In addition to the PFT connection there were Tees to the gravity drainage system served by the supernatant pumping station. ... Hibernia unit serving the RSHT This unit is newly commissioned by Engenica. It was in good condition throughout. Unfortunately the media was found to be dry. On investigation the ball valve serving the washwater break tank was found to be jammed closed with rag and sludge. The washwater tank was empty and the irrigation pumps had stopped on dry run protection. Recommendations: Review the screening provision on the washwater station. Review the suitability of the 13mm ball float valve for screened effluent. Discussion At the time of the visit the level of abatement offered by the units collectively was close to zero. This was due to a number of reasons not including process capacity. Operations will need to review the maintenance and operating regimes for these units taking into account their age and condition. The bioscrubbers are in poor to average condition but due to the non-degradable nature of the filter medium and their GRP construction they are still suitable for extensive M&E refurbishment with an asset life restored of at least ten years. The “Gaps” forwarded separately demonstrate there is no potential to serve additional sources utilising the existing assets. We will need to explore options after the report on ventilation is received from Alec Butcher.”
“Inlet Works – East & West The 20 ton skips are thought to be contributing to smell by the length of time screenings are sitting in the skips combined with the high temperatures generated within the containers by the sun beating down on the outside. Hales are investigating re other installations to see if these problems are encountered elsewhere. Drager tube checks for H 2S will be carried out by Adrian, although it is felt that smells will not be generated by H 2S rather than decomposing fat etc. The potential for smell caused by sewage aerosols from the screens to be checked. Alan will be reviewing inlet wks area re smell with Chris [Collier] today. Storm Tanks Odours are generated due to storm overflow occurring more frequently than it would, as a result of increased flows to East side. Once the new works is commissioned and the West side is taking a higher proportion of flows this situation will improve. Sludge Odours have been caused by failure of the liquor pumping station and the diverted flows going to the Main PS. Currently temporary pumping arrangements avoid this by discharging to the PSTs as normal. Sludge thickening issues are all to be addressed as part of the project. The centrifuge, once installed, will alleviate the overloaded PFTs. It is likely the bioscrubbers are overloaded by higher levels of H 2S than they were designed to cope with as a result of PFT overloading. The bioscrubbers themselves were checked by Ian Cranshaw last week and faults found: The calcified seaweed bed irrigation is not operating, Alan is chasing Engenica on this. One bioscrubber tower air fan was found to be too small and a replacement is being organised. The other unit is not operating and this is being rectified. Chemical dosing The ferrous dosing has been problematic, currently the dosing pump has failed. The ferric dosing system will be completed before the new year and will be the backup.”
“3) East Side Skip Compactors require a daily washing procedure or additional mods to allow an automatic washing facility to remove foul stinking leachate from under the skips. Rag spillages must be cleaned up on a daily basis to prevent the rags from festering until they are removed. 4) Maintenance of All Storm Water Tanks must improve and speed of repair to facilitate returning of storm sewerage with the tanks being scraped to minimise odour problems.”
“either reduce residence time in outer skips or use odour control chemicals. Trial of latter (global odour) likely to take place but not until warmer weather”. (2) In relation to storm tanks and return, the odour issue was stated as “length of time required to drain storm tanks. Now takes 14 hours each by pumping only – previously by decanting took 4 hours. This equates to 7 days to drain the lot as opposed to less than 2 days previously. Mechanical scrapers not now Best Practice”
“At present the bio-scrubbers are not sampled for H 2S checks as there is no safe access – to be rectified under future Projects. The bio-filter has yet to be fully commissioned and handed over.”
“The sewage arriving at the works inlet is anaerobic and is therefore likely to be prone to the production of odours at the primary sedimentation stage. Introduction of ferric chloride has proven successful in controlling odours and this chemical dosing may be required on a long term basis.”
“Other sources of odour were the East-side Primary and Secondary Sedimentation Tanks and both works inlets, settled sewage feed channel on the East-side to the B battery aeration plant and the area around the power house.”
“There is no doubt that the Achilles heel of Mogden is the PFTs which were installed in approx. 1996, initial design calcs showed 6 were needed but the decision was taken at the time to try and push the process to utilise 4 only. Hence the process when co-settling is hopelessly overloaded and can’t generally cope with the throughput rates required. This has a knock on effect of creating a backlog of sludge in the works which especially the Secondary Settlement Tanks (SSTs) causes a proliferation of odour as it gradually turns septic waiting to be removed from the tanks. This is particularly prevalent on the East side of the works.”
“The purpose of this document is to define how the potential and actual generation of odour from the Mogden STW site is identified and, as far as reasonably practicable, controlled. The format is in line with that adopted for other Thames Water sites. DEFRA has issued a draft Code of Practice, and guidelines on preparing Odour Management Plans are being developed by UKWIR as part of a Best Practicable Means Guide for odour control at wastewater treatment sites.”
“a general septic odour is associated with the East-Side works caused either by odorous substances in the incoming trade wastes or by septicity problems in the rising main.”
“Odour in Weavers Close the entire weekend. Inlet Weir Screening House Shutter doors left open again!!! Skips of rotting waste left on site in the baking sun for the weekend. Another weekend ruined due to Thames Water’s gross incompetence. Quite pathetic.”
“The FST provision in the UWWTD extension was theoretically capable of treating 810Ml/d based on an SSVI of 80ml/g + 20% safety factor when all the other design assumptions were also met. Actual SSVI values have been and continue to be above 80ml/g, although normally the activated sludge settles very well in the laboratory SSVI test.”
“The SSVI at Mogden generally runs between 40-60ml/g. Therefore designing to 80ml/g would not be considered risky. If we designed the extension on an SSVI of 80ml/g and for whatever reason the SSVI increased to 100ml/g (ie as a consequence of insufficient air caused by an air blow, shock load etc) the maximum flow to the FSTs will be reduced as indicated in Table 2. ... The number of additional FSTs is identical for both the Conventional extension and the Chemical Dosing options. In the case of the nitrifying plant no additional FSTs are required unless we design for an extension of 450 TCMD and using an SSVI of 120ml/g, in which case 3 FSTs are required.”
“We are satisfied with the changes to the odour reduction scheme because you have estimated that the amended proposal will deliver greater odour reduction (66.4%) compared to the currently approved scheme (54.9%) based on your April 2005 survey. We note that there are no material changes in costs from those we had amended. Therefore we accept your proposal. ...”
“it has been identified that the scum removal in the Eastside PSTs is not very effective. Some remedial work has been identified which should be carried out to prevent a build-up of scum which, in warmer weather, adds to the odour problems.”
“The PFT had been shown to be incapable of treating the sludge production at Mogden STW to a thickness required to enable the sludge digesters to work at the correct temperature to stabilise the sludge. Problems with the PFT date back to their commissioning in March 1992. The main cause of the problems is that PFTs do not work with sludges that are septic and are likely to produce gasses which prevent consolidation. The MSTW primary sludges are likely to be septic due to the long retention time in the sewerage system and in the PSTs. Extended retention times in overdesigned PFTs make the problems with gassing more serious. Further, sludge from the co-settlement of primary and activated sludge has long been accepted as unsuitable for treatment by PFTs. Records of the continuing problems with the PFTs in the late 1990s when most of the co-settlement had ceased should have alerted TWUL to the need to reengineer this stage of treatment as a matter of urgency. It not only failed to do this but also failed to appreciate that the additional sludge from the UWWTD scheme and the proposed work on the sludge digesters would put unacceptable loads on an already over-stretched sludge treatment plant. UWWTD scheme is estimated to have added some 10% additional sludge production due to the additional flows being treated including flows from Kew STW and the use of chemicals to assist primary settlement. This would result in more primary sludge without a corresponding reduction in the amount of secondary sludge. Drum and belt thickeners and sludge centrifuges were widely available in the late 1990s for this type of duty, but the recognition of the need to abandon the PFTs and move to this type of technology at MSTW occurred only gradually through to 2003.”
“The Defendant’s approach to sludge consolidation was in line with the rest of the UK water industry. The initial installation of Picket Fence Thickeners (PFTs) in 1992 was seen as the best technology for thickening co-settled sludges, as defined in the WRc UD 819 document. It is recognised that the loadings used at MSTW were lower than the recommended loadings defined in the WRc guideline. Although installing 6 PFTs instead of 4 PFTs, in 1992, would not have resolved the issue that PFTs do not operate well when fed with co-settled sludge. In 1995 the Defendant recognised the performance issues associated with gravity thickening of co-settled sludges, this was in line with other UK water authorities. 1995-1999 the defendant moved (in stages) from gravity thickening of co-settled sludges to primary sludge only. At this point the loadings were well above the WRc required loading rates. In fact once the PFTs were operating on primary sludge then only two of the four tanks should have been required. The secondary sludges were thickened separately by industry best practice gravity belt thickeners and centrifuges. This arrangement of gravity thickening of primary sludges and mechanical thickening of secondary sludges is seen as best practice approach and also on a global basis. July 2001, combined with the digester refurbishment, Thames recognised the need for reduced digester volumetric throughput and thus looked to increase the thickened sludge dry solids concentration. July 2001-April 2002, defendant trial all UK water industry recognised mechanical thickening equipment. Through trial, drum thickeners are selected and first machine installed in April 2002, two more installed in April 2003.The selection of drum thickeners in 2002 was very new to the water industry, but this choice was now reflected across a great deal of sites across the UK.”
“Progressive deterioration of the Mogden digestion process over many years, coupled with increased works loadings and greater sludge make has put pressure on the entire process such that digestion periods and temperatures achieved are insufficient to give complete stabilisation of the sludge…; since installation of centrifuges to accelerate clearance of the site the underlying problem has manifested itself in odour generation. Recent installation of gravity sludge thickeners has been unsuccessful due to the presence of co-settled surplus sludge - a process constraint now fully recognised. The urgent need is to remove a substantial portion of the SAS from the gravity thickener stream and to provide an effective but temporary alternative to allow evaluation of performance, an immediate improvement in the digester feed sludge thickness and consequent reduction in odour problems.”
“There is no doubt that the Achilles heel of Mogden is the PFTs which were installed in approx. 1996, initial design calcs showed 6 were needed but the decision was taken at the time to try and push the process to utilise 4 only. Hence the process when co-settling is hopelessly overloaded and can’t generally cope with the throughput rates required. This has a knock on effect of creating a backlog of sludge in the works which especially the Secondary Settlement Tanks (SSTs) causes a proliferation of odour as it gradually turns septic waiting to be removed from the tanks. This is particularly prevalent on the East side of the works.”
“The major source of odour at Mogden Sewage Treatment Works is digester gas escaping into the atmosphere in the anaerobic digester area. Elimination of digester gas emissions would greatly reduce the overall odour problem at Mogden. It is recommended that Mogden anaerobic digesters be sealed to prevent escape of digester gas, either using flexible seals between the fixed wall and the floating roof or by conversion of the tanks to fixed roof digesters. Satisfactory technology for the implantation of flexible seals on the existing floating roof digesters is not available but it may be possible to develop suitable sealing methods. If this is not possible, replacement by fixed roof digesters may be required.”
“It is considered that the digesters are no longer the major source of odour. We have installed two different odour control devices in the digester area: lute seals where the dome sits, and a water seal as opposed to a sludge seal has been fitted on two digesters. The third digester has a rubber seal fitted around the annulus of the dome. Current gas flow problems from digesters have been addressed by an Engineering Capital Scheme. The occurrence of inconsistent bell heights is thought to be due to these problems as well as the weight differences between newly refurbished bells and the older, more corroded bells.... If the gas flow problems can be resolved, allowing us to minimise the bell heights of digesters, then further odour control of individual digesters may not be necessary. The refurbishment of digesters will continue of a rolling programme until 1998.”
“The first step in reducing the impact is to identify measures by which the current treatment process and operations can be optimised to minimise the generation of odours at source. Based on our investigations conducted during this study, the recommendations described below are made. … Modify the gas management system for collection of gas generated from the digesters to prevent release of gas directly to atmosphere. Prevention may require provision of suitable odour control (e.g. carbon filters) to ensure that any remaining releases are treated prior to entering the atmosphere.”
“The other key source of odour associated with the sludge treatment area is release of gas from the digesters. It is understood that the regular release of gas is due in part to the current operational regime of balancing the extraction rate of digester gas from each digester to the gas engines. Due to the significant variation in the generation of gas from each digester at any given point, balancing of extraction cannot be sufficiently controlled to prevent release. Although in overall terms, the total odour emission associated with the release of digester gas is relatively low, it is important to note that concentrations of these releases are likely to be extremely high (measurements conducted in 2003 indicated concentrations of over 80,000ouE/m3). As a result, the gas will require considerable dilution before the odour is reduced below the threshold. Such releases are therefore highly significant in terms of complaint behaviour and must be avoided if a satisfactory reduction in impacts off site is to be achieved.”
“Digester clearing blowing off gas-sufficient to blow sludge onto the ground. Especially on the digester bell at its top level. Recommend review of options.”
“The initial appearance of the units is very poor this is largely due to ponding of sewage effluent around the units from a leaking flange on the main body of one unit. The local flooded area has accelerated the corrosion of the cable trays and supports in the area. Both units had fans running but one unit showed no flow apparently due to a broken fan drive belt. The adjacent unit showed a really low shaft speed on the fan, the motor had been replaced with a unit 50% smaller (in physical dimension). ... The ductwork was in poor condition with some taped joints and a clearly asymmetrical system without balancing dampers between the PFTs.”
“The PFT area currently has two bioscrubbbers. Until recently the pipe work to these had been in disrepair and therefore it is believed that the media in them was dead. Both units would benefit from an overhaul to ensure they are operating effectively.”
“Poor apparent performance no water supply, air supply needs checking.”
“Performance virtually nil - Urgent Attention required as this is pumping out high levels of H 2S.”
“PFT Odour Control (Bioscrubbers) to be correctly sized, flooding of Rh Unit rectified and fully operational by31 March 2000 .”
“We understand that the temperature of the pasteurised sludge will be above ambient and therefore the air being extracted is likely to be at a higher humidity. This makes it even more important that the vessel and duct work drains are checked regularly for blockage, particularly during the winter. The original design basis for the odour control unit was for the carbon media to have a 2 year life based on an average odour level of 20ppm H 2S. We are aware that the odour levels are often in excess of this concentration but are unsure whether the plant modifications will result in the odour control unit having to deal with a further increase. However during our installation period, we did detect a slight odour from the unit that may suggest that a carbon refill is overdue.”
“If these benefits are to be fully realised in the longer term, it is of course imperative that these units are maintained. From this perspective, regular monitoring of the treatment efficiency of the plant is recommended, particularly for the carbon unit serving the imported sludge tank which will require regular media replacement at the light loads noted during the survey.”
“The Sludge Thickening OCU is currently achieving an odour removal efficiency of 91% for odour and 98.2% for hydrogen sulphide. However, the carbon unit does not appear to be functioning, and as a result the residual odour concentration released from the unit is higher than expected for a unit of this kind (-38,000 ouE/m3). The results suggest that the carbon contained in this unit has reached the end of its operational life and is in need of replacement.”
“The Pasturisation unitOCU is currently achieving an odour removal efficiency of >99% for both odour and 99.8% for hydrogen sulphide. The residual odour concentration released from the unit is however higher than expected, measured at 21,000 ouE/m3. This high residual concentration may be due to overdosing of hypochlorite chemical in the scrubber system, which gives the treated air a distinctive ‘swimming pool’ odour. It is recommended that the operational conditions and dosing set-points for this unit are reviewed to assess whether there is any room for modification to better match the odour load presented to it.”
“arising from the release of malodorous gases detectable outside the process boundary including Hydrogen Sulphide, Mercaptans and all other gases associated with, and as a by-product of, the processing and treatment of sewage.”
“2. To carry out weekly tests of all odour abatement plant, including biofilters and bioscrubbers, to maintain records of the results of such teats for at least 24 months, and to provide copies of such records forthwith upon request by [LBH]. Such tests shall be for hydrogen sulphide and carried out with a meter of at least 1 ppb (part per billion) resolution for outlet concentration measures. 3. To carry out at least annually olfactory performance tests on all odour abatement plant, including biofilters and bioscrubbers and to maintain records of the results of such tests for at least 24 months... ... 8. Provide a copy of the Works Odour Management Plan (OMP) and on a continuing basis supply within 30 days copies of revisions to this plan. ... 13. The OMP shall include trigger/action levels in respect of (a) hydrogen sulphide emissions from bioscrubbers and biofilters and (b) sludge volumes in the PSTs. ... 14. The OMP shall also include proposals for regular odour monitoring at suitable locations at the site boundary and for trigger/action levels in respect of measured hydrogen sulphide concentrations at such locations. ...”
“7.1 ...Thames Water has developed a capability to carry out a wide range of odour measurement and assessment techniques include odour mapping, olfactometry, chemical analysis, atmospheric dispersion modelling and emission rate measurement. This section reviews these methods. The process coordinators for each works area will be able to help with mapping techniques and assessment of the site. ... 7.6 Dispersion modelling Two of the best known atmospheric dispersion modelling methods are the Gaussian Plume model and Computational Fluid Dynamics (CFD). Thames Water R&D owns copies of two implementations of these models and are reviewing the potential for these methods for assessing the potential spread of odour from a new STW and the impact of remedial works at existing sites.”
“As there are a number of odour sources at Mogden which should not emit odours dominated by H2S, such as the aeration lanes and effective odour abatement plant (OCUs), I feel that dispersion modelling would be better based on olfactometric techniques than H 2S, but I fully accept that with careful interpretation H 2S could have also been used.”
“Additional odour problems would be caused if solids remaining in the storm tanks are exposed during emptying. It is recommended that the sludge and debris be scraped out whilst still under supernatant cover.”
“Nuisance defined The essence of nuisance is a condition or activity which unduly interferes with the use or enjoyment of land. In common parlance, stenches and smoke and a variety of different things may amount to a nuisance in fact but whether they are actionable as the tort of nuisance will depend upon a variety of considerations and a balancing of conflicting interests. An actionable nuisance is incapable of exact definition, and it may overlap with some other heading of liability in tort such as negligence or the rule in Rylands v. Fletcher. Nuisance is an act or omission which is an interference with, disturbance of or annoyance to, a person in the exercise or enjoyment of (a) a right belonging to him as a member of the public, when it is a public nuisance, or (b) his ownership or occupation of land or of some easement, profit, or other right used or enjoyed in connection with land, when it is a private nuisance.”
“So, in the instant case, if as a matter of interpretation of the Act it is clear that the intention of Parliament was to change the immediate environment of the village of Waterston by the construction upon the specified site immediately beside the village of a great oil refinery with jetties appropriate to the berthing of large tankers bringing in vast quantities C of crude oil, and a railway to carry the products of the refinery away overland, it would follow that Parliament had authorised a dramatic change in the neighbourhood of the village. Thereafter a complaint of nuisance by interference with the enjoyment of life in the village would on any view have to show such a degree of interference with enjoyment as exceeded such levels of noise and impurity of air as are inevitable in a neighbourhood in which oil refinery business is to be regarded as the norm. This perhaps difficult question of fact is not the same as the question whether the refinery has been constructed and operated with due regard to the application of such mechanical and chemical devices as will minimise interference with the lives of the inhabitants of the village, i.e. the question of negligence in the special sense in which breach of the duty of care is described in this context. So if it is right to hold as a matter of construction of the Act that it was not the intention of Parliament to grant the defendants a licence to invade the common law rights of the inhabitants by subjecting them to any degree of interference with their comfort and convenience by noise, vibration, or air pollution, there will still remain the question whether the complaints of the plaintiff are such as to constitute a nuisance having regard to the changed character of the environment which Parliament has authorised.”
“We are here in the well charted field of statutory authority. It is now well settled that where Parliament by express direction or by necessary implication has authorised the construction and use of an undertaking or works, that carries with it an authority to do what is authorised with immunity from any action based on nuisance. The right of action is taken away: Hammersmith and City Railway Co. v. Brand (1869) L.R. 4 H.L. 171, 215 per Lord Cairns. To this there is made the qualification, or condition, that the statutory powers are exercised without " negligence "— that word here being used in a special sense so as to require the undertaker, as a condition of obtaining immunity from action, to carry out the work and conduct the operation with all reasonable regard and care for the interests of other persons: Geddis v. Proprietors of Bann Reservoir(1878) 3 App Cas 430 , 455 per Lord Blackburn. It is within the same principle that immunity from action is withheld where the terms of the statute are permissive only, in which case the powers conferred must be exercised in strict conformity with private rights: Metropolitan Asylum District v. Hill (1881) 6 App.Cas. 193.”
“When Parliament has authorized a certain thing to be made or done in a certain place, there can be no action for nuisance caused by the making or doing of that thing if the nuisance is the inevitable result of the making or doing so authorized. The onus of proving that the result is inevitable is on those who wish to escape liability for nuisance, but the criterion of inevitability is not what is theoretically possible but what is possible according to the state of scientific knowledge at the time, having also in view a certain common sense appreciation, which cannot be rigidly defined, of practical feasibility in view of situation and of expense.”
“... the first question is "What did the Legislature authorize?" The sections can be read as directing the use of such a plant as was originally erected or even as relieving the Corporation from liability for nuisance on proof that all due care has been used. The case becomes one of quite a simple proof. I think the condition of freedom from liability is proof of due care but not that any particular plant or user can be implied from the general terms employed. The appellants are right in saying that the Manchester Corporation Act, 1914, is not a "special Act" within s. 1 of the Electric Lighting Clauses Act of 1899, but in effect varies or excepts the operation of the scheduled clauses of that Act. What is required of them is to use all due and reasonable means and precautions to avoid a nuisance. The burden of proving that they have done so is on them.”
“...it is abundantly clear that one important purpose of the enforcement scheme in the 1991 Act is that individual householders should not be able to launch proceedings in respect of failure to build sufficient sewers. When flooding occurs the first enforcement step under the statute is that the director, as the regulator of the industry, will consider whether to make an enforcement order. He will look at the position of an individual householder but in the context of the wider considerations spelled out in the statute. Individual householders may bring proceedings in respect of inadequate drainage only when the undertaker has failed to comply with an enforcement order made by the Secretary of State or the director. The existence of a parallel common law right, whereby individual householders who suffer sewer flooding may themselves bring court proceedings when no enforcement order has been made, would set at nought the statutory scheme. It would effectively supplant the regulatory role the director was intended to discharge when questions of sewer flooding arise.”
“24. Sewerage undertakers receive no subsidy from public funds for works of this nature. The cost has to be met out of money received from customers by way of sewerage charges. But sewerage undertakers are not at liberty to fix the amount of sewerage charges at whatever amount they wish. The Director sets limits on these charges. Sewerage charges in respect of dwellings are the subject of charges schemes which require the approval of the Director: sections 142 and 143(6). In setting the limits on charges the Director proceeds on the basis that companies are expected to maintain current service levels. 25. In fixing charging limits the Director balances the need to alleviate sewer flooding, the cost of doing so and the consequent increase in sewerage charges. He also has to take into account further needs such as the need for investment to meet other environmental standards set by the government, often pursuant to EU Directives, and the need to maintain the sewerage infrastructure as a whole. It seems that in the past a cautious approach has been adopted by the Director, partly because of the lack of reliable information about the scale of the sewer flooding problem and the cost of dealing with it.”
“34. In my view the cause of action in nuisance asserted by Mr Marcic is inconsistent with the statutory scheme. Mr Marcic's claim is expressed in various ways but in practical terms it always comes down to this: Thames Water ought to build more sewers. This is the only way Thames Water can prevent sewer flooding of Mr Marcic's property. This is the only way because it is not suggested that Thames Water failed to operate its existing sewage system properly by not cleaning or maintaining it. 35. On the contrary, it is abundantly clear that one important purpose of the enforcement scheme in the 1991 Act is that individual householders should not be able to launch proceedings in respect of failure to build sufficient sewers. When flooding occurs the first enforcement step under the statute is that the Director, as the regulator of the industry, will consider whether to make an enforcement order. He will look at the position of an individual householder but in the context of the wider considerations spelled out in the statute.”
“...we confirm that in the event that the Court determines that our client failed to take steps which it owed the Claimants a duty to take, our client admits that funding would have been available to it to take such steps whether or not our client was able to raise the necessary funding through customers’ bills.”
“In the water industry, the Director considers that future improvements in levels of service should be achieved without higher price limits, as in other utilities. … For most water companies, progress towards achieving the improvements proposed in [business plans] should be possible without any special provision being made in the price limit. However, some water companies and most sewerage companies have produced in their [business plans] a scale of enhancement to levels of service over and above those than can be achieved solely through the measures outlined above. In Setting Price Limits for Water and Sewerage Services, the Director explained that he would expect customers to finance such additional enhancements through increased prices only where the company has made an exceptionally strong case… For many companies the Director concluded that there is neither a pressing need for the scale of improvement in service levels proposed nor sufficient evidence of collective customer support to justify any allowance in price limits. In a number of cases, affordability has been critical issue because of the high level of existing bills.”
“The Director does not consider that prices need to be increased to allow for other improvements to customer service proposed by the companies. Much has been achieved by the companies over the last five years without any specific allowance in prices and a number of companies have committed themselves to making further service improvements from efficiency savings. The Director believes that the right approach is to provide strong incentives for cost-effective improvement in the areas most valued by customers.”
“Later this year Ofwat expects there to be a non-statutory code of practice for managing odour at sewage treatment works. We will expect each sewerage company to develop its policy and strategy for odour management to reflect the practices, processes and technologies recommended in this code. Plans to meet and maintain compliance with the code will form part of the output expectations for each company for AMP4. We require each company to demonstrate why and how its policy for odour management has or will change from AMP3, the consequences of changes in policy and how the company has developed, appraised and adopted the strategy upon which its AMP4 and onward investment proposals are based. To date we have considered management of odour to be an integral element of a company’s functions and carried out as a matter of course consistent with its established policy. Companies’ established policies should provide for maintaining good operational practice to minimise odour risk (good housekeeping) and the provision, operations and maintenance of routine odour control measures. Odour control measures should take site-specific circumstances into account, both odour generation, control and impact on the surrounding environment. We recognise that companies may be under increasing public pressure to mitigate the impact of odour, and that the forthcoming code may, in some circumstances, require some companies to implement measures that go beyond their established policies and practices…”
“It is proposed to deal with odour at sewage works at a greater rate than currently, by implementing technical solutions to resolve process stream problems at an additional five sites per year. The Thames Water Odour Working Group have scoped and costed each site identified and prioritised as having odour management needs. As many of the technical solutions to be implemented such as washpacters, chemical scrubbers and ammajets, are relatively new for Thames Water, we do not have sufficient data to generate cost models. Our approach has therefore been to use the AMP3 cost model methodology with the best available data. The Estimated capital costs is£9.9 m over the 5 year period and is over and above the current levels of expenditure in AMP2 of£7 -8 m on odour control which has been included in Capital Maintenance. The annual operating cost of£0.1m relates to additional costs for chemicals and power. The impact on the average bill is estimated as 20p.”
“The proposal to deal with odour from sewage treatment works has been dealt with consistently with proposals included within the company’s quality programme. Ofwat has not included and allowance for these improvements as such problems should be resolved through normal business operations.”
“We note, with disappointment, that you have chosen not to allow any expenditure for other service areas such as supply interruptions, resource deficiencies, odour control. We do not believe that the package you propose in the Draft Determination will allow us the scope to achieve these improvements for our customers from additional efficiency savings.”
“Thames has assessed and costed in some detail, specific works at each site to reduce odour. This approach is appropriate and, in our opinion, the enhanced service level expenditure proposed for odour control is a reasonable estimate for the new assets needed to reduce odour from the 25 treatment sites identified.”
“The AMP3 determination contained no specific allowance for odour problems at any site, the Ofwat view being that “improvements to deal with odour should be resolved through normal business operations”
“In addition, operators have access to a variety of funding mechanisms apart from “additional funding” through customer bills, e.g. reallocation of resource priorities, efficiency gains, borrowing and profits. Regulated sewerage companies may need to fund abatement measures and invoke the regulatory price adjustment mechanisms that may be available to them.”
“This year we have unfortunately observed a rapid increase in mosquito activity and consequently a corresponding number of complaints. This had been brought about by a number of factors including (i) early wet spell followed by the recent heat wave leading to high humidity and therefore producing ideal breeding conditions. (ii) larger than usual number of over-wintering adults, (iii) numerous blocked drains, spillages, leakages and building defects leading to many areas of standing stagnant water and (iv) difficulties in treatment of breeding areas such as digesters due to the risk of explosion due to the presence of methane gas.”
“Project Drivers ... The scope of work to be provided under this project is to remove or reduce some of the significant over-wintering areas at the site. Where it is not practical to remove, the project will improve access to areas of the site to make spraying more effective and hence improve the value gained from the OPEX being spent to control mosquito numbers. Some scope is also required to make the spraying activity safer through improved access provisions. ... Project Justification ... Mosquitoes are able to survive and reproduce readily during the summer but require still, warm water to survive over the winter. Mogden STW has a number of areas that provide ideal over-wintering sites, such as digester galleries, aeration galleries and the main pumping station drywell. This allows a large population of mosquitoes to survive and breed, and impact local residents and staff. With the elimination or reduction of the most significant over-wintering sites, it is expected that the summer nuisance would be decreased and may delay outbreaks. Whilst not eliminating the operational spend, over a number of years a reduction may be expected. ... Options ... CAPEX- a full assessment of all over-wintering activity has been undertaken with consulting entomologists. The level of investment has been challenged and value managed to identify those two areas where CAPEX spent will have high impact on mosquito activity....”
“The objective of this project is to reduce the number of mosquitoes by reducing the number of over-wintering sites. A decrease in the frequency and amount of spraying is also to be expected with the completion of this work. TW’s consulting entomologist has identified the main over-wintering sites as the lower galleries between the sludge digestion tanks, the basement of the power house, the galleries at the south ends of aeration lanes 1 to 18 , pumping station 5 just north of the sludge digestions tanks and pumping station 4, just south of aeration lanes 6 and 7. ”
“The digestion tank galleries are the worst areas for winter infestation and comprise an upper and lower level. The floors of the upper galleries have openings by each digestion tank. In galleries 2 and 3 these openings have steel Technocovers fitted, with the remaining having a removable steel grating fitted. Sludge spills and constant high temperatures in galleries 2 to 5 create ideal breeding conditions for Culex Pipiens. The 150mm drains for the sampling sinks to each digester are reported to be blocked with concrete and cannot be cleared by the jetting unit. There is also visible debris in the drains for tanks 5, 11, 15, 16, 17 and 19. Galleries 1-3 are directed by sumps, located in the centre of each gallery and connected to a dedicated low-level 150 mm drain. Galleries 4 and 5 presently contain large amounts of stagnant water/sludge and were originally drained by a sump pump in each gallery, which discharged into the sink drains. Flexible 50 mm hosing, which was reported to block frequently, was later installed for each pump to bypass the blocked sink drains and discharged directly into the sump in gallery 3. Both pumps are no longer functional and will be replaced by the Purchaser’s Operations Team with submersible pumps manufactured by Flygt ... and using the original 50mm hosing.”
“Repair drainage to Digester Sump 4. The drain in sump 4 of the Digesters has been blocked for over 10 years, causing water to back up in sumps 4 and 5 (the latter drains into 4). Frequent leakage of sludge into sump 4 has produced conditions ideal for winter breeding of [Cp Molestus]. This is probably the most important wintering site for the mosquito in Mogden STW. Although regular spraying, together with drainage from the top, have improved the situation, this remains the most important engineering work on site for mosquito control. If the drain was repaired, sumps 4 and 5 could be maintained in a dry condition and winter numbers of mosquitoes would fall to a lower level. We understand that this is difficult to achieve and would be expensive, because the drain is set in deep concrete at the bottom of the digester chambers.”
“Flushing the Storm Tanks and inlet channels In summer the Storm Tanks and their inlet channels are often left standing for long periods and become heavily infested with mosquitoes. They should be flushed regularly to prevent large mosquito populations building up. It is not possible to spray such a large area effectively, thus prevention of mosquitoes by mechanical means is the only real option for control. The new systems of draining the ‘hoppers’, which are left wet when the tanks are drained, is useful, but regular flushing is still necessary.”
“1. Everyone has the right to respect for his private and family life, his home, and his correspondence. 2. There shall be no interference by a public authority with the exercise of this right except such as is in accordance with the law and is necessary in a democratic society in the interests of national security, public safety or the economic wellbeing of the country, for the prevention of disorder or crime, for the protection of health or morals, or for the protection of the rights and freedoms of others.”
“I consider that when the court awards damages for nuisance to those with a legal interest that will usually afford just satisfaction to partners and children but that there might be circumstances where they will not. In the case of Thomas Bannister, he lives in the same household as his parents who will receive damages for the loss of amenity of their property. There is nothing in the claim to show that such damages received by the household would not afford just satisfaction as they did for Mrs Dennis or would have done for Mr Marcic. I conclude that those damages would afford Thomas Bannister just satisfaction.”
“45. We have considerable sympathy for the judge's conclusion as to Issue 9, i.e. that there should be no separate award under Article 8 to Thomas Bannister. However, in the state of the law which we have set out, we would disagree with the judge that it is possible to give an answer at this stage. If one takes the case of Thomas Bannister as the test case, it seems to us that those representing him can show that he has not, personally, had "reparation" under English law (see Article 41). But we do not think it can be regarded as irrelevant whether his parents recover damages in nuisance or what sums they recover because all the circumstances need to be taken into account in considering whether an award is necessary. Furthermore s.8(3) seems to us expressly to require to be taken into account any remedy granted "in relation to the act in question" and "the consequences of any decision … in respect of that act" without limiting the same to remedies awarded in favour of the person alleging infringement of his rights. The vital question will be whether it is necessary to award damages to another member of the household or whether the remedy of a declaration that Article 8 rights have been infringed suffices, alongside the award to the landowner, especially when no pecuniary loss has been suffered. If, for the reasons explained above in paragraphs 32-34, the effects of the odour and mosquitoes upon Thomas Bannister personally were in practice taken into account in determining the diminution in the amenity value of the property, and therefore in determining the amount of damages awarded to his parents in nuisance, we would regard that as a highly significant consideration when determining whether an award of damages was necessary to afford Thomas just satisfaction under Article 8. In any event the fact of an award to the parents, if made, and its amount, must be a circumstance relevant to whether an award is necessary. 46. For these reasons, we do not think it is possible to say until the case has been tried out whether it is just and appropriate and necessary to award some damages to Thomas Bannister if he is to have just satisfaction. For the reasons given, it may very well be that a declaration is sufficient in his case, but it will depend on the judge's findings in relation to his parents and to any particular consideration affecting Thomas. Even if it is thought that necessity be shown, the fact of any award to his parents, and its amount will be relevant as to quantum. It should be noted that in any event damages if awarded on such issues are not substantial.”1083.The Court of Appeal considered, first, the basis on which damages in private nuisance are to be assessed as set out in Hunter v Canary Wharf[1997] AC 655 . At [31] Waller LJ summarised the position in Hunter v Canary Wharf as follows: “31. The speeches of the majority thus clearly establish that damages in nuisance are for injury to the property and not to the sensibilities of the occupier(s). That is so as much for the case of the transitory nuisance interfering with comfort and enjoyment of the land as it is for the case of the nuisance which occasions permanent injury to the land and to its capital value, or other pecuniary loss.”
“Otherwise, it is perhaps inevitable that the assessment of damages for loss of amenity will involve a considerable degree of imprecision. But if estate agents are to assist in placing a value on the relevant intangibles, whether by calculating the reduction in letting value of the property for the period of the nuisance or in some other way, we would expect them in practice to take into account, for the purposes of their assessment, the actual experience of the persons in occupation of the property during the relevant period. It is difficult if not impossible to see any other way of proceeding. As Lord Hoffman observed, the measure of damages for loss of amenity will be affected by the size and commodiousness of the property. If the nature of the property is that of a family home and the property is occupied in practice by a family of the size for which it is suited, the experience of the members of that family is likely to be the best evidence available of how amenity has been affected in practical terms, upon which the financial assessment of diminution of amenity value must depend.”
“35. As a result It follows that the actual impact upon the occupiers of the land, although not formally the measure of common law damages for loss of amenity, will in practice be relevant to the assessment of such damages in many cases, including such as the present where a family home is in question and no physical injury to the property, loss of capital value, loss of rent or other pecuniary damage, arises. 36. In our view not one of the speeches of the majority provides any support for the view that the person who has the right to sue in nuisance is recovering damages on behalf of other occupiers of the property.”
“41. It follows that where a public authority has been found to have acted "unlawfully" the court "may grant such relief or remedy …as it considers just andappropriate". No award of damages is to be made unless, taking account of allthe circumstances including any other relief or remedy granted in relation to thesame act, the court is satisfied that the award is necessary to afford justsatisfaction. In determining whether to award damages, or the amount, the court must take into account the principles applied by the European Court under Article41. We have underlined what seem to us to be important aspects of the exercise that a court must perform.”
“In the following paragraph Lord Woolf said that in considering whether to award compensation and, if so, how much, "there is a balance to be drawn between the interests of the victim and those of the public as a whole" and that the court has "a wide discretion in respect of the award of damages for breach of human rights". He described damages as "not an automatic entitlement but…a remedy of last resort." Later, at paragraph 66, in discussing the principles applied by the Strasbourg court, he said that the approach is an equitable one and that "the 'equitable basis' has been cited by the Court of Human Rights both as a reason for awarding damages and as a basis upon which to calculate them"... The Convention serves principally public law aims; the principal objective is to declare any infringement and to put a stop to it. Compensation is ancillary and discretionary. The interests of the individual are part of the equation, but so are those of the wider public. 43. This broad discretionary approach to the award of compensation is no doubt the reason for what has been identified by the joint report produced in October 2000 of the Law Commission and the Scottish Law Commission (Law Com No 266) (Scottish Law Com No 180), as the "lack of clear principles [in the Strasbourg case-law] as to when damages should be awarded and how they should be measured". (See paragraph 3.4). All one can say with any certainty is that damages have been awarded for non-pecuniary loss, i.e. for inconvenience and distress, in pollution cases. What is not at all clear is quite how Strasbourg would view claims brought by more than one person in a household and how it would react to the fact that one member of the household had recovered damages for nuisance in the courts of a Member State.”
“As regards other applicants, the Court notes that they are still residing within the zone. The Court notes that the resettlement of them in an environmentally safer area (a measure sought by the applicants before the domestic instances) would be only one of many possible solutions. The Court is conscious that there are other possible ways of reducing the negative effects of the plant's activities on those who, like the applicants, reside in the vicinity of it. Therefore, given the complexity of the situation, and in line with its approach to Fadeyeva v Russia[2005] ECHR 55723 /00, the Court will not prescribe any particular legal, administrative or other measure to be adopted by the Government. According toart 41 of the Convention , by finding a violation of art 8 in the present case, the Court establishes the Government's obligation to take appropriate measures to remedy the applicant's individual situation. Subject to monitoring by the Committee of Ministers, the respondent State remains free to choose the means by which it will discharge its legal obligation under arts 41 and 46 of the Convention, provided that such means are compatible with the conclusions set out in the present judgment (see Scozzari and Giunta v Italy[2000] ECHR 39221 /98 at para 249), in particular, with the two alternative solutions examined by the Court (see para 110 above).”
"(1) A claimant is prima facie entitled to an injunction against a person committing a wrongful act, such as continuing nuisance, which invades the claimant's legal right. (2) The wrongdoer is not entitled to ask the court to sanction his wrongdoing by purchasing the claimant's rights on payment of damages assessed by the court. (3) The court has jurisdiction to award damages instead of an injunction, even in cases of a continuing nuisance; but the jurisdiction does not mean that the court is "a tribunal for legalising wrongful acts" by a defendant, who is able and willing to pay damages: per Lindley LJ at pages 315 and 316. (4) The judicial discretion to award damages in lieu should pay attention to well settled principles and should not be exercised to deprive a claimant of his prima facie right "except under very exceptional circumstances." (per Lindley LJ at p 315 and316). (5) Although it is not possible to specify all the circumstances relevant to the exercise of the discretion or to lay down rules for its exercise, the judgments indicated that it was relevant to consider the following factors: whether the injury to the claimant's legal rights was small; whether the injury could be estimated in money; whether it could be adequately compensated by a small money payment; whether it would be oppressive to the defendant to grant an injunction; whether the claimant had shown that he only wanted money; whether the conduct of the claimant rendered it unjust to give him more than pecuniary relief; and whether there were any other circumstances which justified the refusal of an injunction: see AL Smith LJ at pages 322 and 323 and Lindley LJ at page 317."