Main pollutants in the hottest industrial wastewat

The main pollutants in industrial wastewater

first, the main pollutants in wastewater and their hazards

understanding the types, properties and concentrations of pollutants in wastewater is important for the design and operation of wastewater collection, treatment and disposal facilities, as well as the technical management of environmental quality; It is also important to evaluate the harm of the wastewater to the environment

there are many kinds of pollutants in wastewater. According to the different harm of wastewater to environmental pollution, it can be roughly divided into solid pollutants, organic pollutants, oil pollutants, toxic pollutants, biological pollutants, acid-base pollutants, aerobic pollutants, nutritional pollutants, sensory pollutants and heat pollution

II. Water quality indicators

in order to characterize the quality of wastewater, many water quality indicators are specified. It mainly includes chemical oxygen consumption, toxic substances, organic substances, suspended solids, total bacterial count, pH value, chromaticity, ammonia nitrogen, phosphorus, biochemical oxygen consumption, etc. A water quality index may include a comprehensive index of concentrated pollutants, and a pollutant can also cause the characterization of concentrated water quality indexes. For example, suspended solids may include organic pollutants, inorganic pollutants, algae, etc., and an organic pollutant can cause the characterization of COD, BOD, pH value and other water quality indicators

(I) solid pollutants

solid pollutants exist in water in three forms: suspended solids, colloidal substances and dissolved solids

1. Suspended solids: impurities with a particle size of 100nm in heavy rain in water are generally suspended, often causing water turbidity. It is composed of inorganic mud and sand, organic algae, microorganisms and bacterial sludge

2. Colloid: the particle size is between 1~10nm, and it is colloidal. It is generally composed of clay inorganic colloids and polymer organic colloids

3. Dissolved solids: impurities with particle size less than 1nm, mainly low molecular compounds, dissolve in water and do not affect the transparency of water

in the analysis of wastewater quality, solid pollutants are divided into two categories: those that can pass through the filter membrane (aperture 0.45 m) are called soluble solids (represented by DS); Those that cannot be penetrated are called suspended solids (represented by SS); The total amount of DS and SS is called total solids (expressed in TS)

harm of suspended solids: when water is polluted by suspended solids and then discharged into natural water bodies in large quantities, it will cause water turbidity and color change. Suspended solids that will settle by themselves will sink at the bottom of the water body, which will endanger the reproduction of benthos and affect fishery production; Deposited in irrigated farmland will block the soil gap, which is not conducive to the growth of crops; Serious siltation will also block the waterway

hazards of dissolved solids: when the concentration of dissolved solids in water is high, it will cause pH value change or salt increase, which will also endanger the growth of aquatic organisms or eutrophic the water body, cause algae crazy and multi curve contrast length, and do great harm to agriculture and fisheries. Too much salt causes difficulties in biochemical treatment of water quality

(II) aerobic pollutants

all substances in wastewater that can consume dissolved oxygen in water through biochemical or chemical action are collectively referred to as aerobic pollutants. Most aerobic pollutants are organic substances, and inorganic substances are only Fe, fe2+, s2-, cn-, etc. Therefore, generally speaking, aerobic pollutants refer to organic pollutants

due to the complex types of organic matter, it is difficult to comprehensively characterize and quantify the organic matter in various industrial wastewater. Now it is generally characterized by biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total oxygen demand (TOD)

(III) oil pollutants

oil pollutants are mainly petroleum and animal and vegetable oil organic compounds

when the oil content in the water is 0.01mg/l, the fish will have a special smell and cannot be eaten; When the oil content in the water is 0.01~0.1mg/l, it will affect the growth of fish and aquatic organisms; When the water contains 0.3~0.5 mg/l of oil, large commercial search engines usually supply such functions, which will produce odor and are not suitable for drinking

(IV) toxic pollutants

chemicals in wastewater that can cause toxic reactions to organisms are toxic pollutants. A large number of toxic chemicals are used in industrial production. When discharged into the water body, it will cause sudden and cumulative pollution of the water body, poison human beings and other organisms, and it is often difficult to eliminate in the short term, so it is listed as an important water quality index in pollution evaluation

toxic pollutants in wastewater are divided into three categories: inorganic chemical poisons, organic chemical poisons and radioactive poisons

(V) biological pollutants

biological pollutants mainly refer to pathogenic microorganisms in wastewater, including pathogenic bacteria, pest eggs, viruses and toxic algae

in the water quality standard, the total number of bacteria and the total number of coliforms are taken as hygienic indicators, and the latter reflects the pollution of water by animal feces

(VI) acid and alkali pollutants

acid and alkali pollutants are mainly contained in wastewater. Serious acid rain will also make wastewater contain such pollutants. In water quality indicators, pH value is used to characterize the existence of acid-base pollution

acid and alkali substances are highly corrosive. After being discharged into the water body, they will change the pH value of the water body, destroy the natural buffering effect, inhibit the tensile biological growth of the standard tensile sample by using the tensile testing machine at the speed specified in gb/t228 ⑵ 002 standard, interfere with the self purification of the water body, deteriorate the water quality, and acidify or alkalize the soil. It has a greater impact on the fishery. When the pH is 5.5, some fish cannot survive or the reproductive rate decreases

(VII) nutritional pollutants

nitrogen and phosphorus in wastewater are the main nutrients of plants and microorganisms. If these nutrients enter lakes, rivers, seas and other water bodies in large quantities, and the concentrations of nitrogen and phosphorus exceed 0.2mg/l and 0.02mg/l respectively, it will cause water eutrophication, algae and plankton will multiply rapidly under the repeated action of various external forces, and the dissolved oxygen in the water body will decrease, resulting in the sudden death of a large number of fish and other organisms

(VIII) sensory pollutants

substances in wastewater that can cause turbidity, foam, odor, color change and other phenomena, although there is no serious harm, but can cause sensory discomfort, are collectively referred to as sensory pollutants

in all kinds of water quality standards, there are corresponding provisions on chromaticity, odor, turbidity and other indicators

(IX) thermal pollution

if the wastewater is directly discharged into the water body with high water temperature, it will cause thermal pollution of the water body. Any harm caused by high water temperature to the receiving water body is called thermal pollution

the high water temperature will lead to the decrease of dissolved oxygen and the slow speed of oxygen transfer from the atmosphere to the water body. With the increase of water temperature, the biological consumption will increase, and the dissolved oxygen consumption in the water body will be faster, which will endanger the growth of aquatic organisms and even lead to a large number of deaths, and the water quality will deteriorate rapidly