Problematic micro-organisms, blockages and the presence of surfactants are amongst the most common challenges in the aerobic treatment process.
By Matthew Smyth, Associate Technical Director, Aqua Enviro
Over the past eighteen years, I have visited hundreds of domestic and industrial effluent treatment plants; many of these sites have at their core an aerobic treatment process, with this most often being an activated sludge plant. When problems are encountered the most common root cause is the aeration system. Be it poor settling sludge, a breach of consent limits for BOD or ammonia, reduced throughput or high energy consumption, this part of the plant is the first area to investigate. Unfortunately, it is also often incredibly difficult to access, on occasions being under up to eight metres depth of mixed liquor.
Question marks over the capacity of the aeration system are more common in the industrial, rather than the domestic, wastewater sector. This is due to the greater variability (composition, flow, characteristics) in the nature of the wastewater to be treated, as well as sites often increasing their production capacity over time without considering the implications on the effluent plant. Industrial effluent plants are also particularly prone to filamentous bulking. Bulking is where micro-organisms grow that reduce the settlement rate (or filtration in membrane plants) of the activated sludge. More importantly, bulking affects the transfer of oxygen from the gas phase to the bubble phase. Herein lies the problem.
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