Water Journal : Water Journal May 2011
110 MAY 2011 water water business water business NEW ARRIVAL IN AUSTRALIAN WASTEWATER MARKET SBR (sequential batch reactor technology) is widely introduced in Australia and overseas as a modern wastewater treatment process. The SBR process enjoys growing popularity worldwide and is based on the principle that treatment of wastewater works significantly better under defined volume conditions. Classic sewage plant technologies (i.e. continuous flow plants) cannot provide the same process stability. The more reliable operational performance of SBR plants can cover a wider range of dynamic wastewater discharges arriving at the plant. So far sewage lagoons and ponds were exempt from the benefits of the SBR technology, as constant SBR process volumes were not achievable due to pond geometry and process. Ten years ago, the German Company GAA mbH created a Constant-Waterlevel-SBR process (CWSBR®) for wastewater ponds, introducing a fully operational SBR system for any type of sewage pond. Due to the reduced structural costs and state-of-the- art construction, savings are substantial and can be up to 50%. Distributed through GWS Technologies, Townsville and Taupo, CWSBR® pond systems are now also available in Australia and New Zealand. Like the original SBR system, CWSBR® is based on modern PLC technology and was also made possible through the development of modern synthetic materials and geotextiles, creating the tools for a dynamic pond technology. CWSBR® combines the principles of a standard above-ground SBR plant with the low-cost installation of a traditional lagoon-type treatment plant. Since batch processes are characterised by periodic changing water levels, common SBR plants use solid tanks or containers as reactors to handle large sewage quantities. In order to transfer SBR technology to a pond structure, replacing concrete walls with an earthworked lagoon, naturally supported by surrounding soils, the initial requirement was to eliminate fluctuations in water level. The CWSBR® system is equipped with "Hydrosails", which are attached to the pond floor. Fixed floats on the top edge keep the sails upright, enabling the Hydrosails to separate the pond volume into the different SBR reactor zones with the simple difference that the volume changes are operated vertically compared to the horizontal changes in a standard SBR configuration (Figure 1). From the primary treatment zone, the CWSBR® system pumps the water into the activated sludge zone. The Hydrosails follow the change in volume passively. With balanced water tables on both sides of the sails, tension and stress is not a problem as the Hydrosails just move with the alternating flows. As the water table throughout the pond maintains a constant level at all times, buoyancy problems for the pond liner caused by fluctuating volumes are unknown and slope stability is not an issue. Development and plants constructed to date The first CWSBR®-plant was built in Germany in 2000 in order to retrofit an existing sewage pond system. After 10 years, GAA's knowledge and experience with pond retrofitting can be summarised as follows: CWSBR® grants full SBR performance including nitrification, denitrification, phosphorus removal by Bio-P and fully stabilised sludge. The attribute that is typical for SBR technology, highlighting that the treatment success is independent from the plant size, also applies for the CWSBR® systems. To date, new plants sizing from 800 PE to 210.000 PE have been designed and constructed. Upgrades of existing ponds and lagoons have been carried out up to 5.000 PE by retrofitting and extending existing wastewater ponds (Figure 2 and 3). Figure 2: CWSBR® is a full performance SBR process in the shape of a pond technology, which grants highest wastewater treatment standards. Figure 3: CWSBR® system under running conditions, showing aerated zone. WaterGEMS® and SewerGEMS HYDRAULIC ANALYSIS SOFTWARE TO MAKE WATER SYSTEMS MORE EFFICIENT WaterGEMS and SewerGEMS come equipped with everything engineers need in a fexible multi-platform environment, from automated fre fow and water quality simulations, to criticality and energy cost analysis, to automated design, bottleneck detection, and water loss analysis. These applications are part of Bentley’s integrated water solution which addresses the needs of owner-operators and engineers who contribute to the infrastructure lifecycle. For more information, see the inside front cover of the May issue of Water Journal, visit www.bentley.com/AWA, or e-mail firstname.lastname@example.org. Figure 1: Comparison of water volume changes of CWSBR® and standard SBR.
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