Common indicators in sewage treatment

The following are 15 core indicators commonly used in sewage treatment and their function descriptions, covering key parameters such as organic matter, nutrients, physical properties and microorganisms:
1、 Organic pollution index
1. biochemical oxygen demand (BOD ₅)
It reflects the oxygen required by microorganisms to decompose organic matter within 5 days, and measures the degree of organic pollution in water.
2. chemical oxygen demand (COD)
CODcr is a commonly used method to quickly assess the pollution degree by measuring the total amount of organic matter with strong oxidants (such as potassium dichromate).
3. total organic carbon (TOC)
Direct determination of carbon content in organic matter to evaluate the effect of sewage treatment.
2、 Nutrient index
1. total nitrogen (TN)
Including ammonia nitrogen, nitrate, organic nitrogen, etc., excessive will lead to water eutrophication.
2. total phosphorus (TP)
The total amount of all kinds of phosphorus, high concentrations of which cause algae outbreaks and destroy the ecological balance.
3. ammonia nitrogen (NH ₃ -n)
The sum of free ammonia and ammonium ions has direct toxicity to aquatic organisms.
3、 Physical property index
1. suspended solids (ss/tss)
SS is the total amount of suspended solids and colloids. TSS emphasizes total suspended particles, which affect the transparency of water and treatment efficiency.
2. turbidity (NTU)
It measures the transparency of water body and reflects the content of suspended particles and colloids.
3.ph value
PH index, affecting microbial activity and chemical reaction conditions.
4、 Dissolved oxygen and process parameters
1. dissolved oxygen (do)
The key to maintain the activity of aerobic microorganisms should be controlled at 2-4 mg/L.
2. oxidation reduction potential (ORP)
Judge the oxidation/reduction state of water body and optimize the nitrogen and phosphorus removal process.
3. sludge concentration (mlss/mlvss)
The microbial content in activated sludge directly affects the treatment efficiency.
5、 Hygiene and disinfection index
1. fecal coliform
It indicates the pollution degree of water body by feces, which is related to health and safety.
2. residual chlorine
Excessive residual chlorine after disinfection will inhibit microbial activity.
Application suggestions
key monitoring points: BOD, COD, TN, TP, SS, do and pH should be given priority attention in conventional treatment.
process control: optimize aeration rate through ORP and do, and adjust sludge return flow through MLSS.