Water Journal : Water Journal November 2011
water NOVEMBER 2011 69 greenhouse emissions • Blower inlet air conditions; • Blower condition, wear, seal, bearing and lubrication system maintenance; • Control system accuracy, response time, instrument cleaning and calibration; • Air distribution system sizing, pipes, control valves and flow measurement; • Diffuser condition, type, internal cleanliness and size of bubbles; • Depth of aeration tank, and diffuser floor coverage; • Strength of mixed liquors, upstream treatment, homogeneity; • Matching of different components in the system. The case studies suggested that potential savings of up to 40% could be achieved from a variety of interventions such as: • Check blower flow rate and head against metered electrical input; • Check system pipework, valves and control set-points for best settings; • Install Real Time Control based on incoming flows and loads and the effluent consent by installing or upgrading PLC controls; • Install ammonia-derived DO control; • Install variable speed drives to surface aerators; • Upgrade/replace diffuser grids, aerator paddles; • Replace blower drive belts with non-slip belts; • Replace/refurbish blower gear boxes (optimise gear ratios); • Consider blowers with no gearboxes and magnetic bearings; • Maintain/refurbish air transfer pipework; • Dedicated team to optimise plant performance/deliver efficiencies. ASP case studies focused on changing dissolved oxygen control to ammonia- based control. Savings of up to 50% have been reported by relatively simple means of changing instruments and control software. In one example, similar benefits were derived from monitoring inlet loads to regulate flow rates, thereby allowing blower output and energy demand to be reduced. Other examples describe improved control over secondary high energy use processes which are seasonal, such as nitrification, but are incidental to the consent standard. On complex sites where more than one treatment stream is operating, the flexibility to change the emphasis between an activated sludge plant and a filter process has obvious advantages. This is also evidence where the need for tertiary treatment may be marginal and could be reduced or avoided by efficient operation of primary and secondary processes. Conclusions and Recommendations The study conclusions can be summarised as: 1. All water conservation and leakage reduction gains, which include pumping within the cycle, will have a proportional reduction in energy consumption. presented at Figure 2. Case Study Example: 20--23% energy savings from PLC controller changes at ASP (Barwon Water, Geelong, Australia). Delivering excellence in pipelines www.kt.com.au A Monadelphous Group Ltd company One pipeline contractor is committed to executing world class projects for its customers.
Water Journal December 2011
Water Journal September 2011