_O & M MANUAL - WEST LANE MOBILE HOME PARK

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Wasting is one of the most important controls available because it manages the most important aspect of treatment, which is the biomass population. It is usually best to waste over longer periods of time, as practical, and when the loading on the plant is at a low point for the day. Drastic changes in wasting should not be made at one time. Rather, the operator should allow the system time to acclimate before another change is made. Activated Sludge Control Factors and Calculations WAS wasting rates influence the following: • Bacteria growth rate • Amount of bacteria available to process incoming waste • Oxygen consumption • Mixed-Liquor settleability • Occurrences of foaming and frothing • The possibility of nitrification • Final effluent quality Determination of Wasting Rate To determine the right target for sludge wasting the operator should consider all the following factors: • Mixed liquor color and concentration (MLSS) • Settleability of the solids (SVI) • The sludge age (SA) • Foam • How much sludge is in the clarifier (Sludge Judge) • Check if solids are rising To optimize sludge wasting,the operator should also consider seasonal influences and only make small sludge wasting rate adjustments as needed. The steps needed to determine the wasting rate include the following: 1. First, determine how much "food" is entering the plant.This is the BOD in mg/I obtained from an outside lab report. 2. Then, calculate the Organic Loading. This converts the BOD from mg/I to lbs/day 3. Next, calculate the amount of MLSS in the aeration tank and send a sample to the lab for a MLVSS test. 4. Then, perform a Settleometer test 5. Calculate the SVI (If low, increase wasting, if high, decrease wasting rate) 6. Calculate "food" to microorganism ratio (F:M), (if high decrease wasting and if low increase wasting).