Electroplating wastewater is toxic and harmful. For example, cyanide can cause acute poisoning death of people and animals, and long-term effects of low concentration can also cause chronic poisoning. Sodium cyanide is used for metal electroplating. Cyanide is a highly toxic substance. The average lethal oral dose of HCN is 50 mg, sodium cyanide is about 100 mg and potassium cyanide is about 120 mg. It can be seen that cyanide is very harmful to human body.
Cyanide is harmful to fish and other aquatic organisms. When the concentration of cyanide ion (CN-) in water is 0.04 ~ 0. 1 mg/L, the fish can die. The maximum allowable concentration of CN- in plankton and crustaceans is 0.01mg/L. The toxicity of cyanide in water to fish is also related to the pH value of water, dissolved oxygen and the existence of other metal ions. In addition, cyanide-containing wastewater will also cause agricultural production reduction and livestock death. Cadmium can cause kidney diseases and cause pain. Hexavalent chromium can cause lung cancer, gastrointestinal diseases and anemia, and it will accumulate in bones, spleen and liver. Therefore, electroplating wastewater must be strictly controlled and properly treated.
A large amount of electroplating wastewater is directly discharged into water without any treatment, which causes serious pollution to surface water, soil and crops. The discharge of a large amount of acid and alkali wastewater causes the corrosion of building foundations and sewers, which is extremely harmful.
1964, Huiming electroplating factory collapsed due to wastewater corrosion foundation; The acidic wastewater from Shanghai Petroleum Accessories Factory has seriously corroded the foundation of the factory building, polluted the water source, made workers uneasy about their work, and at the same time, the contradiction between the factories and the groups is sharp. During the period of 1965, the wastewater from Shanghai Electroplating Factory corroded the foundation of the workshop, which made the workshop in a dangerous state. The construction wastewater of Shanghai Traffic Equipment Factory not only corrodes the factory building, but also corrodes the urban sewers, and the Urban Construction Bureau will not allow it to continue to be discharged; During the period of 1979, electroplating wastewater from Asian knife factory and other units was discharged at will, which caused the chromium content in nearby well water to exceed the standard by dozens of times, and the public reacted strongly and stopped production for a time.
The suburbs of Shanghai are the main bases for vegetable cultivation. In 1960s, because of the pollution of electroplating wastewater, the water quality of rivers was affected, which led to the reduction of vegetable production and the deterioration of quality. There are 32,000 mu of vegetable fields in five communes such as Peng Pu, Jiangwan and Dachang in the suburbs, accounting for 22.8% of the vegetable fields in the suburbs of the city. The water quality of farmland irrigation is 65438 0.6 times higher than the provisional standard of agricultural irrigation, and the chromium content is more than 7 times higher. In Chuansha County, the sewage from the sewage pipe in the southern district is used for irrigation. Compared with the control area, the cadmium content in the soil of sewage irrigation area increased by four times, and zinc and copper also accumulated more. In Mayibang area, five electroplating factories, including Shanghai Electroplating Factory, Shanghai Electric Electroplating Factory, Shanghai Kai Guanchang, Pioneer Motor Factory and Medical Machinery Electroplating Factory, discharge cadmium-containing wastewater. The first three factories consume 23 tons of cadmium every year and discharge 49,800 cubic meters of untreated cadmium-containing wastewater to Ant Bank every month. The cadmium content in wastewater is 0.4 ~ 29.5 mg/L, which is 3 ~ 294 times higher than the trial standard of industrial wastewater discharge (0. 1 mg/L). The average cadmium content of main irrigation water sources in this area 16 is 0.336 mg/L. Because of the serious pollution of irrigation canals, the cadmium content in soil is also high. According to the regulations of Japan at that time, the cadmium content in taxi soil was more than one kilogram 1 mg, and the soil pollution area in this area was more than 600 mu. The average cadmium content of vegetables collected from polluted areas is 0.268 mg/kg, which is 0.027 mg/kg 10 times of that of vegetables in control areas.