Basic knowledge of sewage treatment

SS:Solid suspended solids, generally measured in mg/L. Generally refers to the solid mass obtained by filtering water samples through filter paper and drying the retained material at 105 degrees Celsius with a constant weight.

COD: Chemical Oxygen Demand, usually measured in mg/L. The principle of COD determination is to use a strong oxidant (potassium dichromate is legally used in China) to oxidize organic matter into CO2 and H2O under acidic conditions. The amount of oxygen consumed is called chemical oxygen demand. CODCr is generally expressed as COD. Advantages of COD: It can accurately represent the content of organic matter in sewage, with a measurement time of only a few hours, and is not affected by water quality. The higher the chemical oxygen demand, the more severe the organic pollution in the water body.

NH3-N: Ammonia nitrogen, generally measured in mg/L. Ammonia nitrogen refers to the nitrogen present in water in the form of free ammonia (NH3) and ammonium ions (NH4).

BOD: Biochemical Oxygen Demand, generally measured in mg/L. The amount of dissolved oxygen consumed by the slight biodegradation of organic pollutants.

TP: Total phosphorus, generally measured in mg/L. Phosphorus containing compounds in wastewater can be divided into two categories: organic phosphorus and inorganic phosphorus.

Coliform count: refers to the number of coliforms present in each liter of water sample, measured in units of per liter.

Total bacterial count: refers to the total number of coliforms, pathogens, viruses, and other bacteria, expressed as the total number of bacterial colonies per milliliter of water sample.

Common Basic Concepts

Anaerobic: The environmental state in which there is no dissolved oxygen or nitrogen in biological wastewater treatment. Dissolved oxygen is below 0.2mg/L.

Hypoxia: In biological wastewater treatment, the dissolved oxygen level is around 0.2-0.5mg/L in environments with insufficient or no dissolved oxygen but nitrogen.

Aerobic: In biological wastewater treatment, there is a state of dissolved oxygen or nitrogen. Dissolved oxygen is above 2.0mg/L.

Aeration: The process of forcibly transferring oxygen from the air to the liquid, with the aim of obtaining sufficient dissolved oxygen. In addition, aeration also serves the purpose of preventing suspended solids from settling and strengthening the contact between organic matter, microorganisms, and dissolved oxygen in the tank, thereby ensuring that microorganisms in the tank can oxidize and decompose organic matter in wastewater under sufficient dissolved oxygen conditions.

Activated sludge: A sludge like flocculent substance formed by various organisms such as bacteria, fungi, protozoa, and protozoa, as well as inorganic substances such as metal hydroxides. Has good adsorption, flocculation, biological oxidation, and biosynthetic properties.

Activated sludge process: a wastewater treatment method that utilizes the coagulation, adsorption, oxidation, decomposition, and precipitation of activated sludge in wastewater to remove organic pollutants from the wastewater.

Biofilm method: A wastewater treatment method that involves contacting and growing biofilms on a fixed support surface to degrade or transform organic pollutants in wastewater.

Air flotation: Air flotation is a method of separating solid and liquid by introducing or generating a large number of fine bubbles into water, causing them to adhere to suspended particles and create a state with a density lower than water. It uses the principle of buoyancy to make them float on the water surface. The ways in which microbubbles are generated include aeration and dissolved air.

Coagulation: The purpose of coagulation is to add some chemicals (coagulants and coagulants) to water, so that colloidal particles that are difficult to precipitate in water can aggregate with each other and grow to the extent that they can naturally precipitate. This method is called coagulation precipitation.

Filtration: In the process of water treatment, filtration generally refers to the process of using granular fillers such as quartz sand to intercept suspended substances in water, thereby clarifying the water. The main function of filtration is to remove suspended or colloidal substances in water, especially small particles and bacteria that cannot be removed by sedimentation technology. It also has a certain degree of removal effect on COD and BOD.

Precipitation: The process of removing suspended solids from water by utilizing the difference in density between suspended solids and sleep, and gravity settling.