废水氧化还原法：把溶解于废水中的有毒有害物质，经过氧化还原反应，转化为无毒无害的新物质，这种废水的处理方法称为废水的氧化还原法。在氧化还原反应中，有毒有害物质有时是作为还原剂的，这是需要外加氧化剂如空气、臭氧、氯气、漂白粉、次氯酸钠等。当有毒有害物质作为氧化剂时，需要外加还原剂如硫酸亚铁、氯化亚铁、锌粉等。如如果通电电解，则电解时阳极是一种氧化剂，阴极是一种还原剂。
Wastewater oxidation-reduction method: the toxic and harmful substances dissolved in wastewater are converted into new non-toxic and harmless substances through oxidation-reduction reaction. This wastewater treatment method is called wastewater oxidation-reduction method. In the redox reaction, toxic and harmful substances are sometimes used as reducing agents, which requires additional oxidants, such as air, ozone, chlorine, bleaching powder, sodium hypochlorite, etc. When toxic and harmful substances are used as oxidants, reducing agents such as ferrous sulfate, ferrous chloride and zinc powder are needed. If electrified electrolysis, the anode is an oxidant and the cathode is a reducing agent.
药剂氧化
Chemical oxidation
废水中的有毒有害物质为还原性物质，向其中投加氧化助剂，将有毒有害物质氧化成无毒或毒性较小的新物质，此种方法称为药剂氧化法。在废水处理中用的最多的药剂氧化法是氯氧化法，即投加的药剂为含氯氧化物如液氯、漂白粉等，其基本原理都是利用产生的次氯酸根的强氧化作用。
The toxic and harmful substances in wastewater are reductive substances. Adding oxidation aids to them can oxidize the toxic and harmful substances into new non-toxic or less toxic substances. This method is called reagent oxidation method. Chlorine oxidation is the most commonly used chemical oxidation method in wastewater treatment, that is, chlorine containing oxides such as liquid chlorine and bleaching powder are added. Its basic principle is to use the strong oxidation of hypochlorite.
氯氧化法常用来处理含氰废水，国内外比较成熟的工艺是碱性氯氧化法。在碱性氯氧化法处理反应中，pH值小于8.5则有放出剧毒物质氯化氰的危险，一般工艺条件为：废水pH值大于11，当氰离子浓度高于100mg/L时，最好控制在pH=12～13。在此情况下，反应可在10～15min内完成，实际采用的20～30min。该处理方法的缺陷是虽然氢酸盐毒性低，仅为氰的千分之一。但产生的氰酸盐离子易水解生成氨气。因此，需让次氯酸将氰酸盐离子进一步氧化成氮气和二氧化碳，消除氰酸盐对环境的污染同时进一步氧化残余的氯化氰。在进一步氧化氰酸盐的过程中，pH值值控制是至关重要的。pH值大于12，则反应停止，pH值7.5～8.0，用硫酸调节pH值，反应过程适当搅拌以加速反应的完全进行。
Chlorine oxidation process is often used to treat cyanide containing wastewater, and the mature process a
t home and abroad is alkaline chlorine oxidation process. When the pH value is less than 8.5, cyanide chloride will be released. The general process conditions are as follows: the pH value of wastewater is more than 11, and when the concentration of cyanide ion is higher than 100mg / L, it is best to control the pH value at 12-13. In this case, the reaction can be completed in 10-15 minutes, and the actual reaction time is 20-30 minutes. The drawback of this treatment method is that although the toxicity of hydrogenate is low, it is only one thousandth of that of cyanide. But the cyanate ion is easy to hydrolyze to produce ammonia. Therefore, it is necessary for hypochlorite to further oxidize cyanate ions into nitrogen and carbon dioxide to eliminate the environmental pollution caused by cyanate and further oxidize the residual cyanogen chloride. In the process of further oxidation of cyanate, the control of pH value is very important. When the pH value is higher than 12, the reaction stops. The pH value is 7.5-8.0. Adjust the pH value with sulfuric acid, and properly stir the reaction process to accelerate the complete reaction.
臭氧氧化
Ozonation
臭氧氧化法是利用臭氧的强氧化能力，使污水（或废水）中的污染物氧化分解成低毒或无毒的化合物，使水质得到净化。它不仅可降低水中的BOD、COD，而且还可起脱色、除臭、除味、杀菌、杀藻等功能，因而，该处理方法愈来愈受到人们重视。
Ozone oxidation method is to use the strong oxidation ability of ozone to oxidize and decompose the pollutants in sewage (or wastewater) into low toxic or non-toxic compounds, so as to purify the water quality. It can not only reduce the BOD and COD in water, but also decolorize, deodorize, deodorize, sterilize and kill algae. Therefore, people pay more and more attention to this treatment method.
药剂还原与金属还原
Chemical reduction and metal reduction
药剂还原法是利用某些化学药剂的还原性，将废水中的有毒有害物质还原成低毒或无毒的化合物的一种水处理方法。常见的例子是用硫酸亚铁处理含铬废水。亚铁离子起还原作用，在酸性条件下（pH值=2～3），废水中六价铬主要以重铬酸根离子形式存在。六价铬被还原成三价铬，亚铁离子被氧化成铁离子，需再用中和沉淀法将三价铬沉淀。沉淀的污染物是铬氢氧化物和铁氢氧化物的混合物，需要妥善处理，以防二次污染。该工艺流程包括集水、还原、沉淀、固液分离和污泥脱水等工序，可连续操作，也可间歇操作。
Chemical reduction is a kind of water treatment method which uses the reducibility of some chemicals to reduce the toxic and harmful substances in wastewater into low toxic or non-toxic compounds. A common example is the treatment of chromium containing wastewater with ferrous sulfate. Ferrous ions play a reducing role. Under acidic conditions (pH = 2-3), hexavalent chromium in wastewater mainly exists in the form of dichromate. Hexavalent chromium is reduced to trivalent chromium, ferrous ion is oxidized to ferric ion, and trivalent chromium is precipitated by neutralization precipitation method. The precipitated pollutant is a mixture of chromium hydroxide and iron hydroxide, which needs to be properly treated to prevent secondary pollution. The process includes water collection, reduction, sedimentation, solid-liquid separation and sludge dewatering, which can be operated continuously or intermittently.
金属还原法是向废水中投加还原性较强的金属单质，将水中氧化性的金属离子还原成单质金属析出，投加的金属则被氧化成离子进入水中。此种处理方法常用来处理含重金属离子的废水，典型例子是铁屑还原处理含汞废水。其中铁屑还原效果与水中pH值有关，当水中pH值较低时，铁屑还会将废水中氢离子还原成氢气逸出，因而，当废水的pH值较低时，应调节后再处理。反应温度一般控制在20℃～30℃。
Metal reduction method is to add metal elements with strong reducibility into the wastewater, reduce the oxidizing metal ions in the water to elemental metal precipitation, and the added metal is oxidized into ions into the water. This treatment method is often used to treat wastewater containing heavy metal ions. A typical example is the reduction treatment of mercury containing wastewater by iron filings. The reduction effect of iron filings is related to the pH value of the water. When the pH value of the water is low, the iron filings will also reduce the hydrogen ion in the wastewater into hydrogen and escape. Therefore, when the pH value of the wastewater is low, it should be adjusted before treatment. The reaction temperature is generally controlled between 20 ℃ and 30 ℃.