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Sources and characteristics of wastewater in the chemical industry

by:BOQU     2023-03-08
The problem of sewage treatment has become the focus of environmental governance in my country. There are various types of sewage and different treatment methods. Xiaoqi will take you to learn more about the sources and characteristics of wastewater in the chemical industry. 1. Tannery Wastewater 1. Sources Tannery process is divided into light leather and heavy leather according to the use of the product, and can be divided into cow leather, pig leather and sheep leather according to the raw material. The tanning process can generally be divided into three sections: preparation, tanning and finishing. Most of the processes in the preparation and tanning sections are chemical treatment processes carried out in aqueous solution, and the waste water mainly comes from these two sections. Tannery wastewater is especially polluted by degreasing wastewater (pig leather), dehairing and liming wastewater, and chrome tanning wastewater. Although the water volume of these three types of wastewater only accounts for 20% of the total discharge, the pollution load accounts for 80% of the total load. 2. Characteristics Tannery wastewater is characterized by complex composition, deep color, high suspended solids, high oxygen consumption and large water volume. Suspended matter: a large amount of lime, broken skin, wool, oil residue, meat residue, etc. CODcr: Most of the materials used in leather processing are additives, lime, sodium sulfide, ammonium salt, vegetable tanning agent, acid, alkali, protease, chrome tanning agent, neutralizing agent, etc., so the COD content is large. BODs: soluble protein, oil, blood and other organic matter. Sulfur: Mainly the sulfide produced by the use of sodium sulfide in the liming process. Chromium: It is the chromic acid wastewater discharged during chrome tanning. 2. Pesticide wastewater 1. Features There are many kinds of pesticides, and the water quality of pesticide wastewater is complex. Contains pesticides and intermediates, as well as toxic substances such as phenol, arsenic, mercury, and many biodegradable substances; ③It has a foul smell and is irritating to human respiratory tract and mucous membranes; ④The water quality and quantity are unstable. Therefore, the pollution of pesticide wastewater to the environment is very serious. The purpose of pesticide wastewater treatment is to reduce the concentration of pollutants in pesticide production wastewater, improve the recycling rate, and strive to achieve harmlessness. 3. Metallurgical Wastewater 1. Source Metallurgical industry has many products, and the production process is divided into series, which discharges a large amount of waste water, which is one of the main waste water that pollutes the environment. The main characteristics of metallurgical wastewater are large water volume, various types, and complex and changeable water quality. According to the source and characteristics of wastewater, it mainly includes: cooling water, pickling wastewater, dust removal and gas, flue gas washing wastewater, slag washing wastewater, and wastewater condensed, separated or overflowed from the production process. 2. Characteristics of wastewater (1) The volume of wastewater is large; (2) The fluidity of wastewater is between waste gas and solid waste, and it mainly spreads through surface water flow, causing pollution to soil and water; (3) The composition of wastewater is complex and the concentration of pollutants High, not easy to purify. It is often composed of suspended matter and dissolved matter, with high COD, heavy metal content, high toxicity, acidic wastewater, and sometimes radioactive substances. The processing process is complex and governance is difficult. Color and odour, malodorous or prone to foaming, presenting an objectionable appearance. 4. Refinery wastewater 1. The source of refinery has a large amount of industrial water, and the production water points are scattered. The source, characteristics and wastewater of wastewater are related to the crude oil processing process, the type of crude oil, the equipment used, the degree of water reuse and the level of maintenance management. and other factors. According to the source of wastewater, refinery wastewater can be divided into the following types: (1) The wastewater generated by the process wastewater production unit mainly comes from the drainage of towers, tanks, and oil-water separators of the refinery unit, which is the main source of pollution, accounting for the total drainage. About 50% of the COD load; (2) The oily wastewater mainly comes from the cooling water of the pump of the refinery unit, the drainage of crude oil and heavy oil intermediate tanks, the ground washing water, the drainage of towers and condensers, and the oily rainwater in the equipment area; ( 3) It is assumed that clean water mainly comes from boiler blowdown water, regeneration waste liquid from pure water manufacturing equipment, and blowdown water from cooling water towers in circulating cooling water fields; It is characterized by large emissions, large fluctuations, a wide variety of pollutants and large content changes, high toxicity, and a wide pH range. V. Coal Chemical Wastewater 1. Source Coal chemical wastewater contains a lot of highly toxic and high-concentration washing wastewater. These substances mainly come from: (1) Wastewater produced after coal purification. (2) It is the wastewater produced in the recycling and processing of some substances. (2) It is the waste water produced during coking and high-temperature processing of coal. (4) Wastewater generated during the process of pressurizing coal to gasify it. 2. Characteristics The wastewater discharged by coal chemical enterprises is mainly high-concentration coal gas washing wastewater, which contains a large amount of toxic and harmful substances such as phenol, cyanide, oil, and ammonia nitrogen. CODcr in comprehensive wastewater is generally around 5000mg/l, ammonia nitrogen is 200~500mg/l, organic pollutants in wastewater include phenols, polycyclic aromatic compounds, and heterocyclic compounds containing nitrogen, oxygen, and sulfur, etc. Typical industrial wastewater containing refractory organic compounds. The easily degradable organic substances in wastewater are mainly phenolic compounds and benzene compounds; pyrrole, naphthalene, furan, and imidazole are degradable organic substances; the refractory organic substances mainly include pyridine, carbazole, biphenyl, terphenyl, etc. . 6. Sources and characteristics of crude oil extraction wastewater Oilfield produced water is extracted from the oil layer together with crude oil. The wastewater not only carries crude oil, but also dissolves various salts and gases in the formation in the high temperature and high pressure oil layer; During the process, a lot of suspended solids are carried out from the formation; in the process of oil and gas gathering and transportation, some chemicals are mixed in; because the produced water contains a large amount of organic matter, and there is an environment suitable for the survival of microorganisms, a large number of microorganisms will also multiply in the wastewater. .
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