Activated Sludge Treatment Extended Aeration (EA) and Sequencing Batch Reactor (SBR) Systems

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2 Activated Sludge Treatment Extended Aeration (EA) and Sequencing Batch Reactor (SBR) Systems General Features KEE Process packaged and purpose-built activated sludge process systems are suitable for biological treatment of domestic and industrial wastewater. Whilst the packaged treatment plants are produced for typical domestic discharges, purpose-built installations to suit the municipal, industrial, commercial, leisure, hotel and trade discharges which have variable characteristics and cannot be accommodated by Activated Sludge Treatment Plants KEE SBR Plant. packaged plants, can be designed and supplied to suit. The customised plants are of modular construction enabling phased construction and extensions as flows and loads increase. Both the packaged and customised plants can be readily adapted for nutrients (nitrogen or phosphorus) removal. Materials of construction for tanks are chosen from GRP, concrete or fused glass coated steel panels. Installation is quick and simple and operation has been designed for low maintenance and consistency of performance. Packaged plants are normally designed to produce high quality effluent with BOD 5 < 20 mg/litre, suspended solids < 30 mg/litre and NH 4 - N < 5 mg/l and can be further improved as necessary. Process Extended Aeration (EA). The whole screened wastewater is aerated in a reactor sized for large retention time followed by settlement of the biomass in a separate tank (final clarifier). This variation of Activated Sludge Process (ASP) readily lends itself to modular design and construction to produce effluent of high quality. KEE Aeration Plant Sequencing Batch Reactor (SBR). Here the incoming wastewater is screened to remove gross solids followed by aeration of the whole liquid waste, including suspended solids. Separation of the biomass takes place in the same reactor tank. For larger flows, two or more reactors may be used in sequence. Higher quality effluents including nutrient removal can be accomplished where necessary. The Conventional ASP treatment process option includes primary sedimentation, aeration of the wastewater followed by final settlement of the biomass before discharging the effluent. This form of ASP plant requires regular removal of primary and surplus sludge and is now the least preferred option of the three variants. 2

3 Sequencing Batch Reactors (SBR) A patented, compact and very adaptable SBR system NuSAF Compact Packaged Plant SBR Cycle KEE Process offers a patented and compact, yet adaptable SBR system that is proven to produce high quality effluents from municipal and industrial wastewater. The reactor tanks can be constructed from Glassfibre Reinforced Polyester (GRP) for small flows, and fused glass coated steel or concrete for larger installations. The packaged plants can be installed below or above ground, depending on site conditions and have a small footprint and low environmental impact. Larger plants are normally installed above ground. SBR s are suitable for treating biodegradable wastewater to high standards which can be discharged direct to a watercourse with approval from the Regulating Authorities. Partial treatment of high strength effluent for discharge to public sewer can also be accomplished. Typical applications include treating wastewater from remote facilities which cannot be connected to public sewers e.g. housing developments, schools, colleges, hospitals, nursing homes, hotels, leisure complexes, camping sites, visitor centres, industrial and office complexes, process industries etc. How does SBR work? 1. The operational cycle of an SBR will vary from one application to another. However, a typical cycle would commence with partial fill of new wastewater into the reactor containing activated sludge. Nutrient removal can occur at this stage if required. Typical layout of single reactor (SBR) 2. Aeration and mixing are commenced approximately 40 minutes into the fill stage, while filling is continuing. Fill and aeration duration of an SBR largely depends on the BOD 5 and COD strength of the wastewater and typically varies between 8-12 hours for BOD 5 values of up to 500 mg/litre, in excess of 12 hours for BOD 5 values mg/litre and increases with higher BOD 5. For industrial wastewater pilot plant testing for treatability and wastewater characterisation is recommended. 3. Settling and decanting (drainage) are achieved by turning off the air supply. After about one hour, discharge takes place. This is achieved in a number of ways but one of the KEE methods is to use a floating decanter that follows the water level. Packaged plants are decanted through electrically operated solenoid valves. Up to two floating decanters can be used in each reactor tank to achieve the desired rate of discharge. The depth of decant liquor is predetermined. Decant time can also coincide with settling time. 3

4 Range of Single Piece Package Plants Sequencing Batch Reactors and Extended Aeration Single piece unit SBR & EA See table below for specific dimensions. KEE Process Sequencing Batch Reactor and Extended Aeration Plants are packaged for treating normal domestic wastewater. It is assumed that the drainage for foul and surface water is separate and therefore the influent would not include any surface water. Where the drainage is combined please consult KEE Process Ltd Technical Sales for appropriate plant selection. Note: Single reactor SBR plants also include a balancing tank and is not shown above, but is part of KEE supply; size and capacity subject to application. 4

5 Range of Single Piece Package Plants Sequencing Batch Reactors and Extended Aeration Single piece unit SBR & EA See table below for specific dimensions. KEE Process Sequencing Batch Reactor and Extended Aeration Plants are packaged for treating normal domestic wastewater. It is assumed that the drainage for foul and surface water is separate and therefore the influent would not include any surface water. Where the drainage is combined please consult KEE Process Ltd Technical Sales for appropriate plant selection. Note: Please consult KEE Process for advice on application of nondomestic wastewater source. Wastewater must have at least 350mg/litre of alkalinity to facilitate nitrification. Note: Single reactor SBR plants also include a balancing tank and is not shown above, but is part of KEE supply; size and capacity subject to application. 5

6 Extended Aeration (EA) An aerobic process for treating biodegradable wastewater The Process Aeration chamber showing fine bubble membrane diffusers EA is an aerobic process for treating biodegradable wastewater to a high quality and plants can be designed for simple operation and reduced attendance. Screened wastewater is treated in an aeration tank designed to provide a retention time of between 24 and 30 hours. The process is continuous with incoming flow displacing an equivalent volume of mixed liquor from the tank. The displaced mixed liquor passes through to a separate settlement tank where the biomass is settled out and returned to the aeration tank to provide the acclimatised activated sludge for continuing treatment. Clarified treated effluent is discharged to a watercourse (subject to approval from Regulating Authorities) or re-used for other non-human consumption e.g. irrigation or recycle for toilet flushing after disinfection. The KEE Extended Aeration plants feature the unique tapered aeration concept where the process air distribution is managed to take account of the higher BOD 5 and COD strength of wastewater at the inlet to the reactor where a higher proportion of process air is introduced. The proportion of air is gradually reduced or tapered as the wastewater is treated through the reactor. This controlled and managed air distribution in the reactor creates an apparent plug flow condition and effects the staging of the reactor internally, thereby increasing the process efficiency of the treatment plant and providing the necessary environment for sustained nitrification of the wastewater. The extended aeration plant is engineered and operated such that the mixed liquor is held at a near constant concentration by a self-regulating process known as endogenous respiration. This minimises production of surplus sludge and reduces the desludging frequency. For small plants, maintenance free, linear blowers are used to provide the process air. Rotary vane blowers are used for larger plants. The whole aeration system is completed using fine bubble diffusers to enable the efficient transfer of oxygen to the wastewater. Schematic of Extended Aeration Other methods of providing oxygen such as surface aerators or venturi aerators can be substituted for blowers and diffusers. The aeration methods are common for both SBRs and Extended Aeration Systems. 6

7 Activated Sludge Treatments Applications Worldwide Process Technologies and Products The KEE Process technology and products are available directly from KEE or through Authorised Distributors or Licensed Manufacturers in most parts of the World. These overseas outlets are dedicated and have technical skills to assist with most applications and can also provide aftersales service provided by KEE Process Ltd. KEE Process SBR use in situ concrete tanks or prefabricated tanks constructed from fused glass coated steel or concrete panels erected on site on prepared base. Fruit juice factory effluent treatment plant using fused glass coated steel panel towers. SBR plant showing difuser network with air header and showing dentrification PELIA media. The aeration system includes high efficiency fine bubble EPDM membrane diffusers and blowers. For ease of site erection the diffusers can be delivered ready mounted on stainless steel pipes which are fed air from the air header. The diffuser system is arranged to provide even distribution of air and adequate mixing of the mixed liquor. KEE use a floating decanter to provide effective removal of settled wastewater from the reactor without disturbing the settled solids. KEE can also include specially designed patented porous media manufactured from a combination of pulverised inert plastic and clay material to provide a large surface area for denitrifying bacterial culture to colonise. This ensures acclimatised culture is always available. The structured denitrifying media is supplied ready mounted in stainless steel frames for locating onto the tank floor as shown in the pictures (left). SBR plant showing decanter and access manway. These images have been supplied courtesy of Herding Abwassertechnik 7

8 Note: Surface Aerators can be supplied for larger installations in place of Blowers & Diffusers. Abbreviated Technical Specification SBR and EA Plants The KEE SBR and EA plants are available with a wide range of specifications. Packaged plants as illustrated in the tables on pages 4 and 5 can be modified to meet site-specific requirements, otherwise the plants offered are configured as follows:- Inlet Screens Coarse and/or fine screens need to be provided at the inlet to or outlet from the treatment plant. These are not included with the packaged plants but can be provided as extra where required. Aeration Blowers: Linear pump type for up to Model 100 and suitable to operate on a single phase power supply of 230V, 50Hz. Rotary vane types for Models larger than 100 and these are selected to operate on a three phase 415V, 50Hz, 4 wire power supply. Diffusers: Fine Bubble Ceramic or Membrane type - discs or tubular. Process Control/Instrumentation Extended Aeration: The requirements are normally simple and the control panel provided includes starters and overload protection for the motors. The sludge return pump for returning sludge from final clarifier to the reactor is timer controlled and this is included in the panel. The panel is housed in a weatherproof enclosure suitable for outdoor installation. SBR: The panel for SBR plant is similar to that for extended aeration plant, but in addition to the normal motor starters the panel also includes a PLC (Programmable Logic Controller) for managing the various sequences of the SBR process. Tanks Balancing, Aeration, Pump Chambers, Final Clarifier The standard SBR and EA packaged plants include glassfibre reinforced polyester (GRP) tanks. The EA plants up to Model 300 and SBR up to Model 250 are supplied as single piece units. Plants larger than these can be supplied as packaged plants of modular configuration. Single piece or modular configured packaged plants are factory built and fitted and are designed for installation below ground. The plants can also be adapted for above ground installation. All structural steel where used within the tanks is galvanised mild steel. Tables 1 & 2 provide dimensions and other details for the packaged plants. Plants for larger flows are designed for site erection and are constructed from concrete or fused glass coated steel panels on prepared foundations. The plant design would be specific to site requirements which would include influent character, source of wastewater and final effluent criteria. Mechanical and electrical installation would be carried out on site. Final Clarifiers (EA Plants only) For Units up to Model 300 the final clarifier is an integral part of the single piece plant. The final clarifier is hoppered to facilitate sludge consolidation and return to the aeration chamber. For larger plants above Model 300, Final Clarifiers are provided as a separate module (see KEE Technical Brochure 2) or can be site constructed with scraper mechanism for sludge removal. Excess Sludge Sludge produced in SBR or EA plants can be dealt with in different ways: Packaged Plants can be sized and applied to include sludge storage within the aeration chamber. The Packaged Plants can be sized or configured to further mineralise the sludge in the reactor to reduce the volume and the frequency of its disposal. Sludge can be stored in separate tanks on site for disposal at a later date. Sludge can be conditioned and de-watered to reduce bulk and disposal costs. Sludge can be digested on site in separate Digesters. Designed and produced by ( PAS 99 Process : IMR Services : IMR Process : FM Services : FS BS OHSAS Process : OHS Services : OHS Process : EMS Services : EMS Specialists in Domestic & Industrial Wastewater Treatment KEE Process Limited & KEE Services Limited, College Road North, Aston Clinton, Aylesbury, Bucks HP22 5EZ, U.K. T: +44 (0) F: +44 (0) E: sales@keeprocess.com W: 8 In keeping with the Company policy of continuing research and development, KEE Process reserve the right to alter specifi cations and dimensions without prior notice. UK KEE Tech Bro