Water & Wastewater Treatment

www.wwtonline.co.uk | WWT | MAY 2014 | 17 Light gauge stainless steel was used for longevity S outhern Water's £300m high efficiency wastewater treatment scheme at Peacehaven, Sussex, is the company's largest ever project. It includes 11km of new sewer tunnel, two pumping stations, the wastewater treatment works and a 2.5km long sea outfall. In order to meet ambitious environ- mental targets for the site, designers had to implement very space-efficient processes, one of which was con- structed and installed by stainless steel process pipework provider BCI Process. The chosen location of a dry valley in the chalk downs just north of the coastal town of Peacehaven, meant that both compactness and low profile were important selection criteria. Allowance also had to be made in the footprint for treatment expansion to meet possible future tightening of discharge consent conditions. In terms of the secondary treatment, it was important to select the most suitable compact treatment process that could fit in the constrained site and deliver the desired outputs. Sites which have the luxury of space typically employ percolating filters with rotating spray bars, but these would have been impossible to implement in this situation. Designers required a high rate biological treatment process with a minimal footprint. The chosen system consists of 10 biological aerated flooded filter (BAFF) cells, using media which is held in suspension by air forced Southern Water STW Stainless steel pipes for BAFF cells through the cells by five blowers deliver- ing air through a common manifold. All BAFF plants work on the princi- ple of partially treated, aerated sewage flowing through a submerged medium upon which the biomass growth at- taches to form the stable concentrations needed to treat sewage at loading rates of between four and ten times that of conventional treatment systems. BAFFs provide high-rate, compact and robust sewage treatment plants that are capa- ble of producing high-quality sewage effluents. Having passed through primary treatment, the wastewater is distrib- uted equally between the 10 BAFF cells. The wastewater flows upwards, together with air supplied by compres- sors, through several metres of floating polystyrene beads. These beads are retained by a concrete slab perforated with nozzles that allow the water to pass but hold back the beads. Biologi- cal treatment is provided by the aerobic micro-organisms that grow on the beads in the presence of nutrients and oxygen, provided by the wastewater and air. BCI Process won the contract to sup- ply and install the aeration pipework in each of the 10 BAFF cells. All the pipework services were constructed from light gauge metric stainless steel to ensure the new installation would provide long lasting service. With the bulk of the fabrication com- pleted at BCI premises, it maintained consistent high-quality fabrication. The Project focus ● Stainless steel to ensure long life ● Offsite fabrication ● Reduced positional welding cuts installation time Andrew Clouds OpeRATiOnS DiRecTOR, Bci pROceSS ● Allowance had to be made in the footprint for treatment expansion to meet possible future tightening of discharge consent conditions ● limited site space required the most suitable compact treatment pro- cess that could fit in the constrained site and de- liver the desired outputs ● The design required a high-rate biological treatment process with a minimal footprint • Drivers second advantage of in-house fabrica- tion was to allow a consistent flow of materials to on-site engineers, allowing them to complete the installation on time and within budget. BCI has been responsible for in- stalling aeration distribution systems for many years at various UK loca- tions. During this time it has worked closely with engineers to develop the engineering design of the system to improve the construction process and provide a better solution for the customer. BCI has become highly proficient in the manufacturing process, which ►

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