ROLE OF SUPPLEMENTAL AERATION IN IMPROVING OVERLOADED FIRST-STAGE RBC PERFORMANCE

A study was conducted to evaluate the effectiveness of supplemental aeration in improving the performance of an rotating biological contactor (RBC) treatment system whose first and second stages were overloaded resulting in very low dissolved oxygen conditions and heavy beggiatoa growth thereby deteriorating process performance. A four-stage RBC having two parallel trains and treating combined municipal and industrial dairy wastewater was used to conduct the research. One train was provided with supplemental air in all stages and the other train, without supplemental air, was used as a control. Daily 24-hour compositie samples were collected at the influent to the RBC and at the end of each stage. Dissolved oxygen, pH, and temperature levels were measured in each stage. Samples were analyzed for soluble COD, ammonia nitrogen, total and volatile suspended solids. Samples were also analyzed for soluble BOD₅ and oxygen uptake rate once a week. The biomass thickness on the discs was measured and growth conditions were noted. The experimental results indicate that RBC units with supplemental aeration demonstrated remarkable performance and ability to adapt to differing organic loading rates. In addition, beggiatoa growth was completely eliminated with supplemental air thereby establishing thinner and active aerobic biomass.