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KEE Do’s & Don’ts to extend the life of a sewage treatment plant and prevent costly maintenance costs.

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Caring for Your Sewage Treatment Plant

Regular inspections and maintenance will help ensure your plant is operating at optimum performance and will maximise the lifespan of your equipment.

Do’s

  • Follow manufacturers’ recommended doses for your water type when using household cleaning products. Soft water requires far less detergent concentration than hard water.
  • Try to use cleaning products little and often so your treatment plant is not overloaded.
  • Use liquids (not powders) in washing machines and dishwashers. Powders re-coagulate into clumps and can cause blockages.
  • Try to spread your clothes washing throughout the week.
  • Stick to the same washing, dishwasher and other cleaning products as the bacteria will work more efficiently with products it is used to treating.
  • Think before you put anything down the sink, toilet or drains.
  • Desludge your plant when required. Click HERE to view our one page KEE EXPERT guide on proficient desludging and how regularly your unit should be desludged.
  • Ensure only toilet paper is flushed down the toilet and used in normal quantities.
  • Leave your plant switched on while you are away or on holiday. Switching off your plant can cause damage to the motor and moving parts as well as kill the biomass.
  • Compost all your organic food waste or use your local council bio-degradable waste recycling service (where applicable) to dispose of organic waste. Do not flush organic waste down the sink or drain.

Don’ts

  • Don’t put sanitary towels, tampons, cotton wool or cotton wool buds, incontinence pads or any baby, cleaning or facial wipes down the toilet.
  • Don’t flush rubber products or other non-biodegradable  products down the toilet.
  • Don’t pour fat, grease or cooking oil down the sink or drains. Fats suffocate the bacteria and inhibit the biological process. Everyday products such as milk, wine or beer increase the organic load and should also not be disposed of through the wastewater system.
  • Don’t use neat disinfectant or bleach. KEE recommends that these products are only used at the minimum concentration possible, as they can restrict the biomass growth within the plant.
  • Don’t tip medicine, mouth wash or any chemicals such as photographic fluid or garden products (e.g. Insecticides, weed killers and fungicides) down the drains as they will damage the biological treatment process.
  • Don’t pour DIY products (e.g. paint, thinners, turpentine and white spirit etc.) or car fluids such as engine oil, anti-freeze, brake fluid etc. down the drains.
  • Don’t allow rainwater, groundwater or large volumes of water (such as those from a swimming pool or Jacuzzi) into the plant. Chlorine kills the bacteria and the excessive water will increase the flow rate through the plant, not allowing sufficient treatment time.
  • Don’t fit a waste disposal unit under your kitchen sink. Disposing of organic matter through the treatment system increases the organic load, creating bacterial overgrowth which will inhibit the treatment process. Only use a waste disposal unit if your plant is specifically designed to accept higher organic loads.

KEE who are a member of British Water, have a copy of their:
Code of Practice – A Guide for Users of Sewage Treatment Systems  to download as a good starting point for information.

KEE Services recommend that your Sewage Treatment Plant should be regularly serviced to avoid any serious future costly problems – contact KEE.

Request a quote for a maintenance contract or call 01296 634500

 

 

 

KEE UK Developed RBC Project goes to Europe

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Low lifetime cost RBC wastewater treatment plant for total nitrogen and phosphorous (nutrient) removal

KEE Process was commissioned to develop municipal wastewater treatment plants and include features to ensure that the plants are designed to operate during the high summer and low winter loads without losing performance, provide low lifetime cost, low capital cost, low energy cost, low day to day operational input and low sludge production rates.

Over the last few years, KEE has provided solutions for total nutrient removal for small, medium and large scale systems and these systems have been type tested by various authorities. There is a requirement for many locations in the sun-kissed Mediterranean that systems are capable of operating during the high summer usage and low winter usage, whilst maintaining the plant performance. In addition to this, the plant must be able to operate without the need for daily or weekly operational input. KEE was required to produce two such systems, one for Southern Spain and one for Northern Spain. Both sites required operation in fluctuating summer and winter conditions.

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KEE 4.5m Diameter RBC – with built in flow attenuation system for plant process optimisation.

Site 1 in Southern Spain (warm sub-tropical climate) The plant in Southern Spain is a site that includes holiday chalets, a golf club, recreation clubs, restaurants and bars. The first phase of the plant had to operate for 10% of the ultimate design load, as the facilities were under construction but, as the facilities were gradually built and occupied, the plant had to keep up with the gradual increase in flows and loads whilst maintaining process performance. In addition, it was also a requirement that the plant was of a modular construction to phase the build programme to spread the capital cost. The first phase module had to be designed to treat 300m3/d of municipal wastewater but also had to cope with gradual increase in load.

The first phase module was required to treat:

  • 300 m3/d,
  • BOD 440 mg/l
  • NH4-N 74mg/l
  • TKN 80 mg/l.

The final discharge consent:

  • SS < 35 mg/l
  • BOD < 25 mg/l
  • COD < 125 mg/l
  • TN < 25 mg/l
  • NO3-N < 13 mg/l
  • PTOT < 2 mg/l

The plant proposed and supplied by KEE included prefabricated Glass-fibre Reinforced Polyester (GRP) Primary Settlement Tanks which provide the facility to separate gross solids as sludge, flow attenuation and sludge storage. This was followed by one 4.5m diameter, five-bank RBC, installed in an in-situ concrete tank. KEE RBCs include a patented flow-management system which provides a flow and load attenuation system for process performance optimisation and also creates the necessary conditions for nitrification – denitrification within the RBC.

The whole RBC is covered with lightweight GRP sectional covers. The RBC was fitted with an automated and fully flexible internal recycle system to manage the nitrification de-nitrification requirement of the plant.

For separation of biological solids generated in the RBC, the system includes a prefabricated hopper bottom GRP radial upward flow settlement tank with effective tank surface area of 19.2m2. The final settlement tank includes a fully automated pump-assisted hydrostatic sludge and scum draw-off system to periodically remove and return the scum and sludge to the head of the PST for co-settlement with primary sludge.

The plant components were built off-site in the UK and delivered, all ready for final assembly on site. KEE built the whole plant and all the internal pipe-work on-site in four weeks and was ready to receive flows shortly after that.

This newly built RBC plant covers an initial build phase on-site. The full development proposed increases over the next few years which will result in 10 systems of this size being built and installed at various times over an agreed time period. The energy consumption for the plant for the current low flow of 200 m3/d is 88 kWh/d. This is projected to be 115kWh/d when the flow reaches the designed high season flow of 300 m3/d.

Spot sample result five weeks after initial process commissioning flow rate of 200 m3/d.

                       INLET              OUTLET
                         mg/l                mg/l

BOD               440                 24.0
COD               716                  79.0
NH4-N               92                   5.2
TN                   98.8               19.2

 

Image-02

KEE 4.5m Diameter RBC – drive system.

Site 2 in Northern Spain (Temperate Climate)

The plant in Northern Spain was for a smaller population in a village of 170 PE initially, but the local authorities required that the plant should be capable of treating the future projected load from 400PE. The important features to be included in the design were that the same plant should be designed to comply with the performance for both the current load and future projected load whilst maintaining the minimal operations cost and sludge management cost.

The design criteria for the plant in Northern Spain were:

  • 17 m3/d for current PE of 170 & 40 m3/d for the future projected PE of 400
  • BOD 600 mg/l
  • NH4-N 75 mg/l
  • TKN 81 mg/l.

The final effluent discharge consent:

  • SS < 35 mg/l
  • BOD < 25 mg/l
  • COD < 125 mg/l
  • TN < 15 mg/l

The plant for this smaller contributory PE was designed and built along similar lines as the Phase 1 module  for Southern Spain and all the equipment was totally factory built, including the RBC which was housed in a GRP tank and also covered with lightweight sectional GRP covers.

Image-03       Image-04

KEE 2.35m Diameter RBC unit – on site installation and ready for receiving flows.

KEE supplied a 2.35m diameter RBC, fitted with patented managed flow system for flow and load attenuation, internal recycle, automated pump assisted hydrostatic FST sludge and scum removal system, together with  built-in flexibility to readily adapt the plant for such a large fluctuation in flows and loads, whilst maintaining full compliance with effluent discharge criteria including full nitrification and de-nitrification.

The plant was commissioned in April 2014 and the performance of the plant is significantly beyond the design expectation. The energy consumption of the RBC is 15kWh/d for the current load and is projected to be 35kWh/d for the future PE of 400.

Results for the 28 days test period on 95 percentile basis is detailed below for a flow rate of 17.8 m3/d.

                       INLET               OUTLET
mg/l                  mg/l

BOD               854                   9.1
COD             1,708                  62.0
SS                  518                  13.0
NH4-N             126                   1.3
TKN                135                  12.1

For both the sites, KEE also included a feature within the plant design to aerobically digest the sludge during low load periods to (a) reduce sludge management costs and (b) to keep the plant fully operational biologically and ready for the onset of the full load period.

The benefits for the client are that the ownership costs are reduced, the carbon footprint is reduced by avoiding long sludge tanker journeys and the plant is maintained in readiness for the increase in flows and loads of the peak period.

Author: Suru Nathwani B.Eng (Chem), Group MD of KEE

To see the capabilities of the KEE Group of companies please visit the KEE Group website.

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KEE AERATION SYSTEM – UPGRADE FOR THE LARGEST CHEESE MANUFACTURER IN THE UK

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KEE Tritons® Dual mode Processor (Aerator/Mixer)

Creamery

Dairy Crest Davidstow Creamery in Camelford is the largest cheddar cheese manufacturer in the UK. The process of collecting and processing milk is a 24/7 operation and therefore in a cheese-making facility like Davidstow effluent is generated round the clock on a daily basis and needs to be treated and disposed of continuously. Effluent from the cheese-making process contains high fat content and BOD/COD concentration.

The Creamery upgraded the effluent treatment plant during 2002/2003 and currently has DAF, a balancing tank, two aerobic reactors and a final clarifier. One of the aerobic reactors is MBR and the second reactor is an extended aeration system.

The original design was based on the MBR treating 60% of the total load and the extended aeration system expected to treat the balance. Due to various operational matters and high power consumption, the site was operating with the extended aeration system, consisting of a 5,000 m3 reactor, treating approximately 60% of the flow. The extended aeration system used helixor aerators for providing oxygen to the mixed liquor and the air was provided by Roots blowers at approximately 0.7bar pressure.

Approximately two-thirds of the helixors were still operational and this meant that one-third of the reactor was not being aerated and consequently was not effective in providing any treatment. The reactor was lacking in adequate mixing and due to the reduced operational volume of the reactor it was necessary to maintain high MLSS at around 7,000mg/l.

A further complication was introduced with high-pressure air at high temperatures increasing the bulk liquid temperature to 23ºC. The combination of high MLSS concentration, high bulk liquid temperature, lack of adequate mixing and the need to operate the reactor at a DO of 3.0-3.5mg/l meant that the blowers were consuming around 150kW of power. It was necessary to replace the disfunctional helixor aerators, as gradually more helixors were beginning to fail and the process was at risk of becoming unstable.

In order to replace helixor aerators, it would be necessary to de-commission the 5,000m3 extended aeration reactor, re-install the aerators and then re-commission the plant.

Whilst this refurbishment was being carried out, the Creamery would have had to make arrangements to dispose of 5,000m3 of mixed liquor and dispose of 850m3/d of high strength effluent for the duration of the refurbishment. Disposal of effluent would need to be continued after the plant had been re-commissioned and until the process was fully established and the effluent discharged from the plant was within consent. In addition to these logistical issues and the high cost of mixed liquor and effluent disposal, the Creamery also had concerns with the ageing Roots blowers, which were consuming approximately 3,600kWh of electrical power, associated maintenance and extremely high levels of noise. It would also be necessary to install 60kW of mixing power to optimise plant performance thereby increasing the power consumption to 5,040kWh/d.

To optimise the process it would also be advisable to introduce lateral mixing in the reactor and again this would have added to the power costs and additional electro-mechanical equipment to be maintained.

Tritons® Dual mode Processor (Aerator/Mixer)

KEE Process has been working with the Davidstow Creamery and their Consultant, Mr. D. Sharpe of Lanson Microbe, for some time to evaluate installation of KEE’s dual-mode Triton® processor which provides efficient mixing and fine bubble aeration for mixed liquors in any activated sludge system configuration. The Tritons® can be installed without de-commissioning the reactor and whilst the existing treatment process is ongoing thereby eliminating the logistics of emptying the reactor contents and finding a temporary solution for disposal of the effluent.

The Tritons® are surface-mounted fine bubble aerators and the aerator operates under water surface, thereby eliminating the atomisation and aerosol effect of the air-water mixture. The blower supplying low-pressure air is a high-efficiency regenerative unit and is quiet in operation. The Triton® injects a plume of fine bubble air and water mixture into the water and this action ensures that air reaches deep into the tank bottom up to a depth of 10m. The air-water mixture forms a cone-shaped plume which increases in its zone of influence with depth and this ensures that all the tank contents are completely mixed. As the Triton® uses low-pressure air, the mixed liquor temperature is not elevated and thus the energy required for process is minimised.

The blower can be controlled using a DO probe and PLC to facilitate effective dissolved oxygen in the mixed liquor as required. During the low-load conditions the blower would switch off but the Triton® would continue to provide efficient mixing to the reactor contents. The benefits of a well-mixed activated sludge reactor are that all the installed volume of the reactor is actively participating in the treatment process, the DO concentration throughout the reactor is homogenised and is always available throughout the tank and all the other tank contents, i.e. activated sludge and the substrate are uniformly distributed and this enables the reactor to operate as a completely stirred tank reactor. The system can therefore be operated at the desired DO set point of between 1.5mg/l and 2mg/l instead of 3.5mg/l previously.

KEE Process provided the necessary process engineering input to the creamery and re-evaluated the reactor design for treating 850m3/d of creamery effluent with influent COD load of 1,682kg/d (2,000mg/l) at a design MLSS concentration of 4,000mg/l, F:M ratio of 0.053, and mixed liquor temperature of 20ºC. The consent for final effluent for the Creamery is BOD < 13mg/l, SS <20mg/l, NH4-N < 5mg/l and PO4-P < 1mg/l/.

KEE concluded that the process required between two and three 48.5kW Tritons® for oxygen requirements but two would suffice for mixing. It was decided to install two 48.5kW Tritons® and these would provide the necessary mixing of the mixed liquor and almost 85% of the oxygen demand. The balance of the oxygen would be provided by the retained existing helixor aeration system as and when necessary. In effect, the Tritons® took over as the primary aeration system and provided the critical mixing vital to any activated sludge process. The Creamery could have installed three Tritons®, in which case the reactor would have been able to handle 30% more load than at present and this option still remains available to the Creamery. In fact the reactor is capable of treating a lot more load with 4 No. Tritons® but beyond that the process becomes limited by the solids handling capacity of the final clarifier.

The Tritons® were installed and commissioned and the existing aeration system was kept switched on to supplement any necessary deficiency in oxygen demand. The Creamery and Mr D. Sharpe monitored the existing variable speed Roots blower operation and concluded that they only need to operate at their lowest speed. They also monitored the D.O. concentration in the reactor and this was found to be consistently uniform compared to before the installation of the Tritons®. They also commented that the Tritons® were extremely quiet in operation.

Power Saving

Since commissioning the Triton® Dual Mode Processors, the power consumption is 2,580kWh/day and this represents a 28.3% drop in energy consumption compared with the previous aeration system. The annual power saving is 372,300kWh. More importantly, the contents of the reactor are now completely mixed thereby providing a true CSTR with uniform distribution of substrate and D.O. With mixing taken into account the annual power saving would be 897,900kWh. In addition to the power saving the noise from the Roots type blower is eliminated.

Conclusion

  • Tritons® can be installed in new plant, or in existing plants for supplemental aeration and/or mixing or for refurbishment.
  • Tritons® can be installed without de-commissioning the aeration reactor.
  • Tritons® are surface-mounted dual-mode processors and provide complete mixing and fine bubble aeration of the reactor whilst operating under water surface.
  • With complete mixing of the reactor contents, the process is completely optimised for performance and energy consumption with lower operational MLSS concentration.
  • The upgraded aeration system enables operation of the reactor at under 2mg/l DO and, apart from saving energy, it also enables control of DO in the anoxic selector tank.
  • Use of Tritons® enables lower MLSS concentration in operation and this will reduce solids loading on the final clarifier which, in turn, improves final clarifier effectiveness in removing solids or enables operation of the reactor at higher SSVI.
  • The use of high-pressure blowers leads to increased temperature of reactor contents thereby increasing energy consumption.
  • It is possible to treat more flow and load in the same reactor by adding further Tritons® to improve mixing or provide additional D.O. or both.

KEE, a BSI Certified Company (IMS, QMS, OHS & EMS) offers domestic and industrial wastewater treatment solutions including lifetime operation and maintenance using RBC, SAF, SBR and Extended Aeration. With 60 years’ experience and over 350,000 installations, KEE have the expertise in design, build and operation of all wastewater treatment plants.

For full information on KEE Technologies and Services call 01296 634500 or visit: The KEE Group Website

KEE SERVICES LIMITED – REFURBISHMENT OF EXISTING TREATMENT SYSTEMS FOR IMPROVED PROCESS PERFORMANCE AND REDUCED LIFETIME COSTS

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KEE Refurbishment of Packaged Treatment Plants

The Anglian Water Systems (AWS) Team undertook such an exercise over a range of small to medium sized treatment plants adapted by the plc from a local council. Instead of abandoning the existing works, KEE Services Ltd with support from their process partners, KEE Process Ltd, were commissioned to survey 11 sites and report the findings. The report was required to include inventory register, feasibility of refurbishment, process implications and improvements with the associated costs of refurbishment. The survey was undertaken and completed over four weeks and a complete report, with a costed refurbishment program for all the sites was submitted to the AWS Team.

The 11 plants varied from 40PE up to 500PE in size and included systems required to reduce BOD and, in some instances, provide fully nitrified discharge with less than 5mg/l ammoniacal nitrogen. All the plants surveyed were of packaged plant construction, single piece or modular, and included primary settlement stage with combined sludge storage, RBC type biological stage and final settlement tank. The report concluded that it was feasible to refurbish all the plants and included a program for refurbishing the plants to a standard where the operators would have the confidence that the plants would provide a reliable and useful life for a further 20 years. Depending on the extent of refurbishment work necessary, the costs associated with the refurbishment varied substantially, but in every case it was much cheaper than replacement. The cost of refurbishment included for supply and installation of new equipment.

KEE Refurb Sequence-01 KEE Refurb Sequence-02 KEE Refurb Sequence-03KEE Refurb Sequence-04 KEE Refurb Sequence-05 KEE Refurb Sequence-06 KEE Refurb Sequence-07 KEE Refurb Sequence-08

This relates to a cluster of small population equivalent installations where all the plants upgraded were over 20 years old and would now have in excess of a further 20 years life and an improved process performance. With all the sites, the outer GRP structure housing the plant was retained and, with the exception of one or two sites, the internal components including the RBC were replaced by brand new factory built units incorporating the latest concepts in mechanical, structural and process engineering.

All the above plants include sectional GRP covers and were replaced to provide the equivalent of a new plant without the high cost and resource required to build one.

Refurbishing Large Wastewater Treatment Works

The KEE refurbishment concept can also be applied to plants serving larger populations which can be electro-mechanically upgraded to show similar benefits and add 20 years or more useful life to the plant. Scottish Water undertook a similar exercise where an existing 4,750PE activated sludge plant needed to be refurbished to bring the plant back to its full performance requirement without necessarily having to re-build the works.

For more information on Wastewater Treatment Plant refurbishment call KEE Services on: 01296 634500 or visit the KEE Services website.

KEE TRITON AERATOR/MIXER OVERCOMES PREVIOUS LIMITATIONS OF OXIDATION DITCH TECHNOLOGY

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KEE FINE BUBBLE AERATION WITH BUILT IN MIXER

Triton-Graphic-(2)

KEE Process Triton

The KEE Triton Aerator/Mixer overcomes the previous limitations of oxidation ditch technology and can be used to revitalise existing oxidation ditches and extended aeration plant or systems based on activated sludge process.

Using the dual mode processor capabilities of Triton Aerator, aeration basins up to depths of 10m can be completely aerated and mixed. Existing Oxidation Ditches (OD) can be retro-fitted and new OD plants benefit with much smaller footprint. Nitrification and denitrification can all take place in a single reactor. With two propellers and a regenerative blower, Triton is able to operate either as an anoxic mixer with the blower turned off, or an efficient aerator/mixer with the blower on.

Multiple Triton units can be arranged to provide extended contact time between air bubbles and water stream, with greater oxygen transfer efficiency. Improved biological treatment results in Biochemical Oxygen Demand (BOD) removal rates as high as 99% in highly contaminated wastewater.

The KEE Triton is the most versatile fine bubble aeration/mixing device for activated sludge treatment systems available with dual functions – aeration and mixing.

KEE fixed price operation and maintenance contracts are available.

For full information on KEE Technologies and Services visit: KEE Fine Bubble Aeration
or call KEE on: 01296 634500

KEE SERVICES LIMITED MAINTAIN WASTEWATER AND SEWAGE TREATMENT EQUIPMENT MADE BY ANY MANFACTURER

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Engineer-02

The maintenance and operation of any wastewater treatment equipment is a specialised task and KEE Services Limited recognises this.

KEE, with its extensive experience of on-site servicing of all types of wastewater treatment and pumping equipment, its technicians have the knowledge necessary to protect its customers’ investment and the environment.

KEE Services offers planned maintenance programmes ranging from an annual visit to full plant operation. Its aim is to respond to all of your urgent servicing and maintenance needs. The KEE Services Team of fully trained Technicians operates on both a local and regional basis to ensure a prompt and reliable service.

  • Emergency Services
  • Planned Maintenance
  • Breakdowns
  • Equipment Refurbishment
  • Plant Operation
  • Spares
  • Ancillary Products

Committed to maintaining your environment

KEE Services Ltd offers Preventative Maintenance, Process Operation and Breakdown Services for all types of treatment plant and pumping equipment, from all manufacturers. KEE Services Ltd supports its UK customers during out-of-hours emergencies by offering a 24-hour manned call out service.

KEE Technicians are trained in long-term servicing and look after over 8,000 installations in the UK. They have sound mechanical and electrical experience, combined with application knowledge, and can identify problems early.

Working on a local basis, KEE technicians give a prompt service and have a good understanding of the conditions and legislations in each area.

Service and maintenance contracts include routine visits to keep equipment from both KEE Process and other manufacturers in top condition and prolong its lifespan.

There is a range of contracts available or a package can be designed specifically. If refurbishment or upgrading is necessary, KEE Services can advise on the alternatives. Site assessment can be made and installations planned for new and existing sites.

For full information visit the KEE Services website or call 01296 634500 to arrange a visit.

 

KEE PROCESS LIMITED HAVE DEVELOPED A NEW SINGLE-PIECE FACTORY BUILT WASTEWATER TREATMENT PLANT TO ADD TO THEIR RANGE

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Developed by KEE the NuDisc© 5000 HD RBC Sewage Plant and Treatment Centre – a new single-piece factory-built plant to add to their range to meet Severn Trent Water’s extremely stringent requirements.

a

Situated in the heart of the Peak District, the village of Hassop in north Derbyshire lies approximately 11 miles east of Chesterfield and 2 miles to the north of Bakewell, and is within the Severn Trent Water’s catchment. The properties subject to the Section 101a application were served by a village drain. This received flows from septic tank high level overflows and discharged to a local un-named watercourse. Local ground conditions were unsuitable for soakaways. Hassop Estate applied, under Section 101a of the Water Industry Act 1991 in December 2007, for a public sewerage system to be provided.

In 2010 STW accepted the need to lay new sewers and treatment system. The new wastewater treatment works was required to treat flow from a population equivalent of 210, and the consent to discharge for this site required that the BOD < 20mg/l, SS < 30mg/l and NH4-N < 5mg/l.

Project background and cost considerations
The construction of the Hassop WwTW involved the laying of approximately 1600m of foul sewer, an intermediate pumping station and a new RBC Unit to serve the Village. The work was undertaken by NMCNomenca as the Tier 1 Framework Partner and as part of S101A Scheme for Severn Trent Water Ltd.

NMCNomenca’s scope of works was for the detailed design, construction and supervision of the whole project from start to finish. NMCNomenca were also in control of the site until handed back to Severn Trent Water Ltd after commissioning and testing.

The project for capital delivery had to take into account CAPEX and OPEX costs to determine lifetime costs for the project over 20 years. This included the capital cost of delivering the project; design, manufacture, delivery and commissioning of the process plant and all site-related costs including provisions for on-site health & safety, environment and personal welfare for site operatives. The second part of the costs related to operational costs and included cost of energy, consumables, spares, labour and process-related costs such as desludging. The overall objective for the consortium is to minimise lifetime costs without compromising any aspects of the project delivery including site work.

Consent standards
The site at Hassop required to treat wastewater from a population equivalent of 210 with design DWF of 32m3/d, FFT of 173m3/d, BOD load of 12.6kg/d, SS of 15.75kg/d and NH4-N of 1.68kg/d. The consent to discharge for this site required that the BOD< 20mg/l, SS < 30mg/l and NH4-N < 5mg/l.

Such consent standards from the Environment Agency are common for wastewater discharge to a watercourse, although for a small works with such a large variation in design flows during dry and wet weather, this does present a challenge to the designers to ensure that the plant performs to requirements under all these conditions throughout the year.

Process plant selection
KEE Process has, over the last 60 years, developed a range of plants to treat wastewater from municipal and industrial sources to similar and more stringent standards where the BOD values could be less than 5mg/l, SS less than 10mg/l, ammoniacal nitrogen less than 1mg/l, phosphorus less than 1mg/l and total nitrogen less than 15mg/l. The range from KEE includes small packaged systems for small flows, modular packaged units for larger flows and in situ constructed plants for populations larger than 5,000 PE.

For the site at Hassop, the largest single-piece factory-built plant available at the time in KEE’s range was not adequate to deal with the flows, so KEE developed a new single-piece factory-built plant to add to their range. The single-piece plant would be factory built and would take into account all the requirements laid out by Severn Trent Water in its specification and the plant would be delivered to site ready to be placed on a pre-prepared concrete slab and backfilled.

The plant would include installation of the remote desludging facilities and internal electrical wiring during the plant construction in the factory. This would, in effect, be a true ‘plug and play’ system with the objective of reducing site-related construction time and costs.

Building a plant in a factory provides a controlled environment and conducive conditions for maintaining quality standards, which are often difficult when the build is undertaken at a construction site under the prevailing conditions, which may include rain, snow, low temperatures and hazardous operating environment.

In addition, a factory-built plant would enable the duration of construction on site to be substantially reduced, as the factory-built plant can be backfilled within a day or two of being delivered. This means that the excavation is not left open for long periods and, in turn, this reduces any health and safety risks associated with working on site with deep excavations and in confined spaces. However, this may have a major impact on the project costs when plants are factory built compared to building on site.

NuDisc®
KEE NuDisc® 5000 includes the primary sedimentation stage with sludge storage, RBC for biological treatment and a hopper final clarifier, all housed in a single structural GRP housing and covered with lightweight GRP covers.

The RBC is driven by a 0.75kW geared motor at a slow speed of 1rpm and is designed to comply with all the structural and mechanical requirements stipulated by Severn Trent Water Ltd.

The FST includes a fully automated descumming and desludging system, for removal of scum and sludge at regular hourly intervals back to the primary clarifier.

The primary clarifier includes remote desludging facility and this is carried out at regular intervals of 90 days when 18.9m3 (5000 gls) of sludge is tankered away.

KEE packaged plants also include flow attenuation within the primary settlement chamber, in order to provide process stability with the large fluctuations in design flows.

The manner in which the attenuation system is organised also enables evening out peaks and troughs in organic load and this attenuation is achieved in the first stage of the biological process.

Designed and built at KEE’s factory, the KEE NuDisc® 5000 was delivered on time on a cold snowy day and was placed in an excavation ready to be backfilled all on the same day.

The plant was fully commissioned to receive flows only seven weeks from delivery – a big achievement for all the parties involved including KEE Process, NMCNomenca and the client, Severn Trent Water. All other site related matter including landscaping, electrical control gear, remote telemetry system and landscaping were completed within timescales.

Operational and maintenance requirements
The operational and maintenance requirements are desludging every 90 days, lubrication of bearings required every six months. With a daily energy consumption estimated at 21kWh/d. The OPEX costs for the site are therefore minimised.

Summary
Although KEE Process does not have comparative lifetime costs for this specific project, the costs for similar projects with other water companies have shown 30% reduction in capital costs compared to other technologies with substantial amount of site related construction and equally a large proportion of savings in operating costs resulting from savings in energy consumption and operational labour requirement.

KEE, a BSI Certified Company (IMS, QMS, OHS & EMS) offers domestic and industrial wastewater treatment solutions including lifetime operation and maintenance using RBC, SAF, SBR and Extended Aeration. With 60 years’ experience and over 350,000 installations, KEE have the expertise in design, build and operation of all wastewater treatment plants.

For full information on KEE Technologies and Services visit the KEE Group website: