The Conventional Five Wastewater Parameters: What They Are and Why They Matter

For wastewater monitoring, a set of five fundamental parameters—pH, Suspended Solids (SS), Ammonia Nitrogen (NH₃–N), Chemical Oxygen Demand (COD), and Biochemical Oxygen Demand (BOD₅)—provides a quick yet comprehensive assessment of pollution load and treatment needs. While some contexts substitute Total Phosphorus for BOD₅, the five‐parameter battery described below remains the most widely accepted baseline.

pH Value

pH measures the acidity or alkalinity of wastewater. Most discharge permits require pH to stay within 6–9 to protect aquatic life and ensure proper biological treatment.

Suspended Solids (SS)

SS refers to insoluble particles (sand, organic debris, microorganisms) suspended in water. High SS harms aquatic photosynthesis and can carry adsorbed heavy metals or pathogens.

Ammonia Nitrogen (NH₃–N)

NH₃–N, the sum of free ammonia and ammonium ions, originates mainly from domestic sewage and certain industrial effluents. Excessive NH₃–N depletes dissolved oxygen and directly poisons fish.

Chemical Oxygen Demand (COD)

COD quantifies the oxygen equivalent required to chemically oxidize all oxidizable substances (mainly organics) in a sample, offering a rapid (2–3 hour) measure of total pollution load.

Biochemical Oxygen Demand (BOD₅)

BOD₅ measures the oxygen consumed by microorganisms over five days at 20 °C while degrading biodegradable organics. It directly reflects wastewater’s treatability and the residual impact on receiving waters.

Together, these five indicators—covering physical (pH, SS), chemical (COD), nutritional (NH₃–N), and biological (BOD₅) aspects—enable operators to assess pollution severity, predict ecological risks, and guide treatment process adjustments with minimal analytical effort