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Technical Description PHYSICAL PRETREATMENT, SEPARATION AND NITRIFICATION INITIATION (may not be required) (NOTE. The following may not be required for nitrification where detention periods of 14 hours or more are anticipated. With reduced solids concentration, the normal calculated aeration de- mand for the batch process is sufficient for nitrification supplementation. Should external nitrifi- cation be deemed necessary, the following procedure is used.) Prior to entering the treatment plant, raw sewage may be collected in a baffled buffer tank. The buffer tank is anaerobic and sized for a detention period that will allow solid/liquid separation, retention of.solids and floatable materials, and promotion of facultative anaerobes by degenera- tion of natural dissolved oxygen levels. The tank inlet and outlet are level and partially baffled, causing retention of a portion of the sol- ids. This retention allows the microorganisms to develop large colonies. This simple collection of solids reduces overall loading to the aeration reactor and hastens the process of converting or- ganic nitrogen to ammonium ions. It also supplies soluble BOD as effluent product/influent wastewater to the aeration tank. The lowering of BOD levels in -the aeration reactor forces depletion of available BOD food source in the extended aeration phase. This enhances the natural dominance of nitrosomonas and nitrobacter organisms. These organisms predominate and utilize the dead cells as a carbon source, converting ammonium nitrogen (NH4),as a nutrient base, to nitrite (NO2) through oxida- tion. A portion of the resulting nitrate (NO3) rises to the surface of the reactor and is reduced prior to reaching the atmosphere. The nitrosomonas are responsible for conversion of ammonium nitrogen to nitrite, which spon- sors the rapid nitrobactcr conversion to nitrate: NH'4+ 3/2 02 --- 2W+H2O+-NO2 (1) and a portion of the NO2 is then oxidized to NO3: NO2 + 1/2 02 NO2 —* NO-3 (2) The use of microprocessor and computer technology allows modifications of the timing cycle that controls the amount of time the sludge spends in the treatment system. It is this cycle that is referred to as the Mean-Cell-Residence-Time (MCRT), and is a function of the amount of food provided to bacteria in the aeration reactor tank(the food-to-microorganism(F:M ratio)). -9- TH Technical Services Group,Inc.