Application of Water Quality Sensors in Sewage Treatment

Dissolved Oxygen SensorExcessively high dissolved oxygen (above 4 mg/L) accelerates the consumption of organic matter in sewage, leading to ageing of activated sludge due to nutrient deficiency for microorganisms and massive propagation of filamentous bacteria. Persistently excessive dissolved oxygen reduces the flocculation and adsorption capacity of activated sludge. By contrast, insufficient dissolved oxygen (below 1.5 mg/L inhibits the vital activities of microorganisms, resulting in their decay, disintegration and deterioration. It impairs microbial respiration and the purification performance of activated sludge, and further triggers sludge floating, putrefaction and even sludge bulking.

pH SensorThe pH value affects the charge on the cell membrane of microorganisms in activated sludge for sewage treatment. It thereby influences enzyme activity during nutrient absorption and metabolism by microorganisms, and alters the availability of nutrients as well as the toxicity of hazardous substances in the growth environment.

ORP Water Quality SensorORP refers to the potential difference between the redox potential of the indicator electrode and that of the reference electrode in liquid, delivering a comprehensive indicator for the redox state of the whole system. A low ORP value indicates a high content of reducing substances or organic pollutants and a low dissolved‑oxygen concentration in the wastewater treatment system, with a dominant reducing environment. A high ORP value means a low concentration of organic pollutants in wastewater and a high level of dissolved oxygen or oxidizing substances, representing a prevailing oxidizing environment. ORP serves as a key development direction for automatic control and anaerobic regulation in sewage treatment plants. It is of great significance for energy conservation, regulation of metabolic pathways of anaerobic microorganisms and improvement of treatment efficiency.

Ammonia Nitrogen SensorAmmonia nitrogen in wastewater denotes nitrogen existing in the forms of free ammonia and ammonium ions. It mainly originates from the decomposition of nitrogen‑containing organic matter in domestic sewage, industrial wastewater from coking, synthetic ammonia industries, and farmland drainage. The oxidation of ammonium nitrogen (\(\boldsymbol{NH_4^+‑N}\)) reduces the dissolved‑oxygen concentration in water bodies, causing blackening and odour generation of water, degrading water quality and threatening the survival of aquatic organisms.