Inorganic and organic indicators in water quality indicators
1) Plant nutrient elements
Excessive nitrogen and phosphorus enter the natural water body, which leads to eutrophication, which causes aquatic plants, especially algae, to multiply, causing drastic changes in dissolved oxygen in the water, affecting fish survival, and possibly causing some lakes to develop from oligotrophic lakes into swamps. And dry land.
2) pH and alkalinity
Generally, the pH of the treated sewage is between 6 and 9 . When the natural water body is contaminated by acid and alkali, the pH changes, destroying or inhibiting the growth of organisms in the water body, hindering the self-purification of the water body, and corroding the ship.
Alkalinity refers to the total amount of substances that can be quantitatively reacted with strong acid in water. According to the state of ions, it can be divided into three categories: hydroxide alkalinity; carbonate alkalinity; bicarbonate alkalinity.
3) Heavy metals
As a trace metal element. Hazard: biological toxicity, inhibit microbial growth, coagulate protein; enriched to the human body step by step, affecting human health.
5) Nitrogen compounds
Nitrogen is a major element in organic matter other than carbon and an important element in the growth of microorganisms. There are four kinds of nitrogen in sewage, namely organic nitrogen, ammonia nitrogen, nitrite nitrogen and nitrate nitrogen.
Hazard: It consumes dissolved oxygen in water; promotes the reproduction of plankton and other plankton, forming water blooms and red tides; causing fish to die, leading to rapid deterioration of water quality.
Several indicators about nitrogen: organic nitrogen: mainly refers to protein and urea. TN : A general term for all nitrogen-containing compounds measured in N. TKN : Organic nitrogen and ammonia nitrogen in TN , excluding nitrite nitrogen and nitrate nitrogen. Ammonia nitrogen: decomposition of organic nitrogen compounds, or directly from nitrogenous industrial wastewater. NOx-N : nitrite nitrogen and nitrate nitrogen.
6) Phosphorus-containing compounds: Phosphorus is also a major element in organic matter and an important element in the growth of microorganisms after nitrogen.
Phosphorus mainly comes from: human waste and synthetic detergents, livestock farms and phosphorus-containing industrial wastewater.
Hazard: Promote the reproduction of plankton and other plankton, destroy the oxygen consumption and reoxygenation balance of water bodies; make water quality deteriorate rapidly and endanger aquatic resources.
Several indicators on phosphorus: organic phosphorus: organic phosphorus includes phosphoric acid, phosphocreatine and the like. Inorganic phosphorus: phosphate: orthophosphate (PO3-4) , hydrogen phosphate (HPO2-4) , dihydrogen phosphate (H2PO4-) , metaphosphate (PO3-) . Polymeric phosphate: pyrophosphate (P2O4-7) , triphosphate (P3O5-10) , hydrogen triphosphate (HP3O2-9)
Organic indicators
1) Total organic carbon (TOC ) : At a high temperature of 950 °C, platinum is used as a catalyst to vaporize the water sample, and then the CO 2 content in the gas is determined to determine the total amount of carbon in the water sample. The content of inorganic carbon should be removed in the measurement.
2) Total oxygen demand (TOD : total oxygen demand) : At 900~950 °C, the substances that can be oxidized in the sewage ( mainly organic matter, including hardly decomposable organic matter and some inorganic reducing substances ) are burned and oxidized into After a stable oxide, the amount of oxygen reduction in the carrier gas is measured and is referred to as total oxygen demand. The measurement is convenient and fast.
3) Chemical oxygen demand (COD ) : The amount of oxidant (O 2 ) (mg/L) converted by chemical oxidation of the organic matter in the wastewater sample. Commonly used oxidants are potassium dichromate K 2 Cr 2 O 7 ( called COD Cr ) and potassium permanganate KMnO 4 ( formerly known as COD Mn or OC , now called permanganate index ) . Under acidic conditions, silver sulfate is the most oxidizing agent as a catalyst. The inorganic reducing substances in the wastewater are also oxidized. If the composition of organic matter in the wastewater is relatively stable, there should be a certain proportional relationship between chemical oxygen demand and biochemical oxygen demand: domestic sewage is usually between 0.4 and 0.5 .
4) Biological oxygen demand (BOD ) : The amount of oxygen (20 °C, 5d) required for microbial oxidation of organic matter in contaminated sewage or contaminated natural water samples under specified conditions. It reflects the main pollution characteristics ( in mg/L ) of the amount of biodegradable organic matter in water under aerobic conditions. The process of oxidative decomposition of organic pollutants by aerobic microorganisms can generally be divided into two stages: the first stage is mainly the conversion of organic matter into carbon dioxide, water and ammonia; the second stage is mainly the conversion of ammonia into nitrite and nitric acid. salt. The biochemical oxygen demand of sewage usually refers only to the amount of oxygen required for the biooxidation of organic matter in the first stage, and all biological oxidation needs to be completed in 20~100d . In practice, often 5d as the standard time measured BOD, said 5 days biochemical oxygen demand (BOD 5); usually at a temperature of 20 ℃ standard assay.
Summary: There is no fixed correlation between TOC or TOD and BOD among various water quality. Under the condition that the water quality conditions are basically unchanged, there is a certain correlation between BOD and TOC or TOD .
5) Oil pollutants: petroleum: from industrial oily sewage. Animal and vegetable oils: Produced in human life processes and the food industry. Hazard: After entering the water body, oil pollutants affect the growth of aquatic organisms and reduce the resource value of water bodies. The oil film covering the water surface hinders the evaporation of water and affects the heat exchange between the atmosphere and the water body. Oil pollutants entering the ocean, changing the reflectivity of seawater and reducing solar radiation entering the surface of the ocean may have certain effects on hydrometeorological conditions in local areas. A large area of ​​oil film will block the oxygen in the atmosphere from entering the water body, thereby reducing the self-purification ability of the water body. Oil pollution is very harmful to juvenile fish and fish eggs. Blocking the crotch of fish can make fish and shrimp produce oily odor and reduce the edible value of aquatic products. Destroy the scenic area and endanger the life of birds.
6) Phenolic contaminants
Source: industrial wastewater such as gas, coking, petrochemical, wood processing, synthetic resin.
Hazard: Protoplast poisons can cause protein to coagulate and cause nervous system poisoning. When the phenol concentration is low, it can affect the migratory reproduction of fish. When the phenol concentration is 0.1 to 0.2 mg/L , the fish has a phenolic taste. High phenol concentrations cause large numbers of fish to die and even disappear. The toxicity of phenol can inhibit the natural growth rate of microorganisms in water, and sometimes even stop it from growing. Phenol can disinfect chlorine with drinking water to produce chlorophenol, which has strong odor (0.001mg/L is odor, emission standard 0.5mg/L) . When the concentration of phenol in irrigation exceeds 5 mg/L , the crops are reduced or even died.
For more information, please pay attention: Yingnuo Instrument (Shanghai) Co., Ltd.
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