Water purification method
Grit chamber: generally located before the pumping station and sedimentation tank. Advection grit chamber (most commonly used), aerated grit chamber (integration of aeration and sand removal, can reduce the organic content in the grit to less than 5%).
Grease trap: A facility that naturally floats to remove oil slicks. Advection type grease trap and sloping plate grease trap. The sedimentation tank is divided into three types according to the direction of water flow in the pool: an advection sedimentation tank, a radial flow sedimentation tank, and a vertical flow sedimentation tank. Neutralizing agent for acidic wastewater: lime CaO, limestone CaCO3, sodium hydroxide NaOH. Neutralizing agent for alkaline wastewater: industrial hydrochloric acid. The advantage is that the solubility of the reaction product is large, the amount of sludge is small, but the concentration of dissolved solids in the effluent is high. Chemical precipitation: Medium and heavy metal ions, alkaline earth metals (calcium, magnesium), and some non-heavy metals (arsenic, fluorine, sulfur, boron) in wastewater are removed by chemical precipitation treatment.
Chemical precipitation process: adding chemical precipitant; solid-liquid separation; sludge treatment and recycling. Flotation method: It is mainly used to treat floating oil in wastewater which is difficult to remove by natural sedimentation or floating, or suspended particles with a relative density close to 1. It includes continuous processes such as bubble generation, bubble and particle attachment, and floating separation. There are mainly (disinfectants) of disinfectants: chlorine, ozone, ultraviolet light, chlorine dioxide and bromine. The method for removing suspended solids from the secondary effluent is: precipitation or stripping after chemical flocculation, and physical filtration. The chemical flocculants used to remove SS are: aluminum compounds, iron compounds, sodium carbonate, NaOH, CO2, polymers. Phosphorus in water generally has three forms: orthophosphate (which can be directly absorbed by organisms), polymerized phosphate (hydrolyzed to orthophosphate, slow process speed), and organic phosphorus (one of the main components of industrial wastewater). Phosphorus removal methods include: chemical precipitation (addition of alum and ferric chloride to lower water pH, lime to raise water pH) and biological methods (A/O process, A2/O process, activated sludge bio-chemical precipitation) Process, sequencing batch reactor SBR). Forms of nitrogen in wastewater (4 species): organic nitrogen (dissolved, particulate, dissolved organic nitrogen mainly in the form of urea and amino acids), ammonia, nitrite, nitrogen. Method for controlling nitrogen content (4 types): biological nitrification-denitrification (inorganic nitrogen delayed aeration oxidation into nitrate, and then anaerobic denitrification into nitrogen); chlorination at the point of secondary chlorination The residual total dissolved chlorine reaches the lowest point, the ammonia nitrogen in the water is completely oxidized); selective ion exchange; ammonia stripping (the secondary effluent pH is increased to 11 or more, the ammonium ion is converted into ammonia, and the effluent is strongly aerated, with gas The way to remove ammonia from the water, and then adjust the pH to the appropriate value). The nitrogen removal rate of each method can exceed 90%.
The role of water purification
Most water purification is provided for human consumption. Purified water can also be used for many other purposes such as medicine, pharmacology, chemistry and industry. Water purification can remove sand, organic matter suspended particles, parasites, Giardia lamblia, Cryptosporidium, bacteria, algae, viruses and fungi, minerals such as calcium, silica, magnesium and some toxic Metals such as lead, copper and chromium.