Application - Wastewater Chemistries - Primary Treatment

Most Frequently Asked Questions  

Parameter Purpose of Test Method
BOD5 Provides a relative measure of "food" available, the degree of stabilization of the wastewater and to estimate the effect of the effluent on the receiving water body. Used for plant loading/design, discharge rate for industrial facilities, and EPA NPDES reporting. 5 day test is too long for process control — many plants use COD or TOC as early estimate. Used to calculate % removal. 8043
Surrogate measurement for solids concentration. Often used to indicate solids carry-over from secondary clarifiers. Turbidimeter (2100xx) See instrument manual
Maintain proper (narrow) pH range for optimal biological processes — especially nitrification. Can indicate plant upsets by industrial discharges or development of anaerobic conditions within the plant. Important condition for methane formation and avoiding ammonia toxicity in sludge digesters. pH meter & electrode - see instrument manual
Solids Most commonly measured and regulated parameter on NPDES permits. Used to measure mixed liquor suspended solids concentration, return activated sludge/waste activated sludge concentration, influent suspended solids concentration, effluent suspended solids concentration, and % removal. 8006
Chemical Oxygen Demand
Used as a correlative/ early indicator of BOD levels. Some NPDES permits include COD as a surrogate for BOD; however, BOD is the standard reportable parameter for oxygen demand in municipal wastewater. COD provides a measure of organic "food" available to biological treatment steps and to estimate the effect of the effluent on the receiving water. (Note: Can be correlated to BOD on a plant-by-plant basis, if influent characteristics are constant.) 8000

Also Consider  

Parameter Purpose of Test Method
Nitrogen, Total Total of ammonia, nitrate, nitrite, and organic nitrogen forms. 10071
Total Kjeldahl Nitrogen
Total of organic and ammonia forms of nitrogen. 8075
Flow Measure standard in-pipe flow rate for NPDES permit requirements and to establish concentrations/total presence of key analytes.  
Oil and Grease Present in wastewater from both animal and petroleum sources. Can affect settlability of solids in waste treatment processes. 10056