What is the key difference between conventional and modified activated sludge processes?

The key difference between conventional and modified activated sludge processes lies in how they manage the microorganisms responsible for wastewater treatment, specifically concerning the presence and behavior of filamentous bacteria. Both processes utilize activated sludge, which is a suspension of microorganisms – primarily bacteria, but also protozoa and other small organisms – that consume organic pollutants in wastewater. This process occurs within a reactor called an aeration tank, where air is supplied to provide oxygen for the microorganisms to break down the waste. Following the aeration tank, the mixed liquor (wastewater and microorganisms) flows to a secondary clarifier, where the microorganisms settle out as sludge, which is then recycled back to the aeration tank to maintain a high microbial population. Conventional activated sludge (CAS) is a relatively simple process. It relies on a balanced microbial com....