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

A study was conducted to evaluate the effectiveness of supplemental ae ration in improving the performance of an rotating biological contacto r (RBC) treatment system whose first and second stages were overloaded resulting in very low dissolved oxygen conditions and heavy beggistto a growth thereby deteriorating process performance. A four-stage RBC h aving two parallel trains and treating combined municipal and industri al dairy wastewater was used to conduct the research. One train was pr ovided with supplemental air in all stages and the other train, withou t supplemental air, was used as a control. Daily 24-hour compositie sa mples 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, t otal and volatile suspended solids. Samples were also analyzed for sol uble BOD5 and oxygen uptake rate once a week. The biomass thickness on the discs was measured and growth conditions were noted. The experime ntal results indicate that RBC units with supplemental aeration demons trated remarkable performance and ability to adapt to differing organi c loading rates. In addition, beggiatoa growth was completely eliminat ed with supplemental air thereby establishing thinner and active aerob ic biomass.