BIOLOGICAL TREATABILITY STUDIES - NEW REGULATIONS REQUIRE A NEW APPROACH

In the past, biological treatability studies were directed toward defi ning effluent BOD and TSS. Recent regulations now require effluent lim itations on volatile organic carbon, specific priority pollutants, aqu atic toxicity and in many cases nitrogen for complex wastewaters. This , in turn, has changed the focus of biological treatability studies. I t is assumed that a screening protocol has been employed to define bio logical treatment as a candidate process [1]. (a) Priority Pollutants- If on or more priority pollutants are a permit issue, a fed batch reac tor (FBR) is run using acclimated biosolids to determine the maximum d egradation rate, q(m), and the half velocity constant, K-s. From these data, the required SRT to meet effluent limitations can be computed. (b) Aquatic Toxicity-If the wastewater exhibits aquatic toxicity in ad dition to priority pollutant requirements, bioassays are run on the bi ological units. Effluent toxicity and COD are tracked with time. Since effluent toxicity is frequently associated with soluble microbial pro ducts (SMP), the SMP is estimated from the effluent COD over time of a eration. (c) Nitrogen-Many organics including SMP are inhibitory to ni trification. The nitrification. rate should be determined on the efflu ents using seeded NH4Cl as a control. From these data, the required SR T can be computed. This paper reviews the required protocols and prese nts several case histories from the chemical and pharmaceutical indust ry.