WET News

Caption if needed sdkvjb sdkvjnsdlk dvsdvdvsdvsdvsdv dv skjbdv lskdjvbsdkljvbsdkv D AFs have been exten- sively deployed within industrial wastewater treatment and by the municipal sector on clean water applica- tions. Traditionally they have been used with chemicals, to achieve a given objective such as solids separation or COD removal, although chemicals are not always necessary for a DAF to be effective. However, DAF processes have not been widely used in municipal wastewater applica- tions at sewage treatment works. Given their successes elsewhere, this doesn't make sense, especially as they can provide a very versatile piece of process equipment, particularly in temporary hire situations, but also in many permanent appli- cations too. Siltbuster Process Solutions (SPS) presented at the Environ- mental Waste Water Manage- ment Conference in 2015, where it educated the industry on the use of DAFs as a viable alterna- tive to other treatment ONSITE SEWAGE TREATMENT 12 WET NEWS JULY 2018 | wwtonline.co.uk chemical addition and 94% with a very low coagulant dose (2 or 3 mg/l as Aluminium or Ferric) (Table 1). The DAFs were used in this instance to provide temporary primary solids sepa- ration, while the existing DAF and municipal wastewater: a versatile option • There is growing awareness of how Dissolved Air Flotation (DAF) can be successfully used throughout the process stream at sewage treatment works, from primary settlement through to tertiary treatment. Chris Bullen, Technical Manager at Siltbuster Process Solutions, talks about DAF processes in more detail TABLE 1 – PRIMARY SOLIDS SEPARATION POST SCREEN Parameter Without Chemicals With Chemicals Concentration (mg/l) Removal Rate (%) Concentration (mg/l) Removal Rate (%) TSS 32 84 25 94 BOD - - 42 42 TABLE 2 – RESULTS FOR LAMELLA – MBBR – DAF WHOLE TREATMENT PROCESS Concentration (mg/l) Sample Unit BODtot BODdiss CODtot CODdiss Ammonia TSS Crude Crude Sewage 300 56 128 Primary Treated HB40R Lamella 151 25 274 56 28.6 86 Biologically treated MBBR30 90 6 159 10 15.1 78 Final Effluent D25 DAF 57 5 47 9 15.3 19 processes. The response SPS received in the wake of this pres- entation was overwhelming. Over 15 schemes have already been completed using Siltbuster DAFs as temporary equipment during refurbishment works, with some of these being pur- chased once the end results were revealed. A key benefit of the SPS unit is that it can be used almost anywhere within the process stream. In primary applications, working alongside Kier Ser- vices, for South West Water at two rural sewage treatment works, SPS showed that as long as inlet flows were well screened, solids removal rates were 84% without the use of

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