According to recent statistics across the country to make pulp papermaking industry wastewater which accounts for 10% 12% of the total sewage discharge, the third, discharge of chemical oxygen demand (cod) accounted for about 40%, 45%, in the first place. Serious pollution and harm of papermaking wastewater has attracted widespread attention papermaking wastewater will typically have three sources:

A, when the pulp fiber separation, bleaching and writing when diluted, squeezing, drying slurry process containing a large number of high concentrations of contaminants such as fiber, inorganic salt and pigment wastewater that blackwater

Second, washing bleaching process produces a large number of containing high concentration of lignin, cellulose fiber and resin acid salt ZhongDuanShui are difficult to biodegradable ingredients

Three, dipping paper machine of eduction contains a lot of fiber, filler and rubber waste water, the water

Is contained in the waste water of the main pollution are the following:

1, the suspended solids Including settlement settlement of suspended solids and suspended solids, mainly fine fiber and fiber material (that is, the broken fiber fragments and mixed cells)

2, easily biodegradable organic matter Including low molecular weight of hemicellulose, methanol, acetic acid, formic acid, sugar, etc.

3, hard biodegradable organic matter mainly comes from the lignin and fibre raw materials contained in the macromolecule carbohydrates.

4, toxic substance Black liquor containing rosin acids and unsaturated fatty acids, etc.

5, acid and alkali toxic alkaline pulping wastewater ph value of 9 ~ 10; Of acid waste water ph value of 1.2 ~ 1.2. 6, chromaticity pulping wastewater contained in the residual lignin is highly coloured.

SS, COD concentration is higher in papermaking wastewater, COD COD by the solubility and solubility of COD in two parts, usually not soluble COD accounted for most of the total COD composition and when SS has been removed in the wastewater, the vast majority of the soluble COD removed at the same time. Wastewater of paper making wastewater treatment, therefore, to solve the main problem is to remove SS and COD.

Most of the paper mill in our country adopts the alkaline pulping black liquor, black liquor contains pollutants accounts for 90% of paper industry pollution emissions, and has the characteristics of high concentration and difficult degradation, its governance has been a big problem. There are three main components of black liquor, namely, lignin, pentose and total base.

Suspended material in papermaking wastewater mainly comes from the bark of preparation section, clippings, sediment, and emissions of soot from a furnace with the water, waste residue, pulp and paper loss in each process of fiber, packing, etc.; BOD in the wastewater from pulp cooking process, such as the production of cellulose decomposing sugar, alcohol, organic acids, etc., in chemistry, cooking effluent BOD5 number accounts for more than 80%; In the wastewater COD and coloring substances mainly come from pulp cooking process of lignin and its derivatives; The toxic substances in waste water mainly include cooking waste liquid of the organic chlorides in crude sulfate soap, bleaching wastewater (such as dichlorophenol, etc.), and trace amounts of mercury, but usually these toxic substances content with little, of bleaching effluent of the toxicity of organic chloride and "three to" role, more and more attention in the developed countries

In pulp and paper industry wastewater, besides containing harmful chemical inorganic matter, also contain solids deposition, volatile phenol, suspended solids, lignin and other organic matter. After this kind of material with the sewage into the water, in the process of microbial decomposition to them, need to consume water dissolved oxygen, oxygen reduction of water, which affects the growth of fish and other organisms. When the dissolved oxygen depletion in the water, the water of the organic matter which produce anaerobic digestion, generate methane and hydrogen sulfide, a stink in water, the survival of harmful aquatic organisms killed a large number of aquatic organisms, destroy the ecological balance, etc.

Such great harm to human body, the waste water containing heavy metals such as lead, etc., used chemicals do not lose efficacy, still can produce great harm to people and environment, if a paper mill near the river, the papermaking wastewater will be discharged to the processing of water after impact on people or the environment, by contrast, small for water for us, who is not willing to drink the water has been polluted, so in the construction of paper mill to avoid building just around the corner. One of the industrial pollution sources. China s paper industry with straw, wood pulp as raw materials for the paper. Papermaking wastewater composition is complicated, but biological sex difference, belongs to industrial wastewater more difficult. Paper belongs to the high concentration organic wastewater and high suspended solids content, biodegradable organic waste water pollution.

Papermaking wastewater treatment methods at home and abroad

1 chemical method

Chemical method is mainly used chemicals, to adjust the pH value of liquid waste, reduce and eliminate the color is given priority to, also have to remove some biochemical oxygen demand and the effect of suspended solids.

2 chemical method

Physical and chemical method including coagulation method, adsorption, membrane separation and some other methods.

2.1 the coagulation method

Tiny particles in the waste water of surface electric charge due to the adsorption of ions. Coagulation method is by Al, Fe and ca salts such as inorganic and amides macromolecular organic matter and suspended solids in the wastewater and organic polymer compounds occur electric neutralization, reduce the potential of colloidal particles z, in the form of adsorption and bridging condensed into large particulate matter sedimentation separation and achieve the goal of clean water. In recent years, a new type of inorganic chemical coagulant such as polymerization, polymerization iron and aluminum composite inorganic coagulant developed, and the development of organic polymer flocculant, the coagulation treatment method can use less reagent, can achieve high treatment effect. With homemade cationic polyacrylamide (PAM) and polyaluminium chloride with waste paper pulping wastewater treatment, water COD5 removal rate above 75%, and through the rate was 92% ~ 92%, and the lower larger flocs, toughness, easy to dehydration

A rate of 92% ~ 92%, and the lower larger flocs, toughness, easy to dehydration.

2.2 adsorption method

Adsorption method is through the physical, chemical or in the form of ion exchange adsorption of pollutants in waste water to the purification of wastewater. The commonly used adsorbent is activated carbon, activated alumina and lime, etc. Have a relatively special adsorption method was ion exchange adsorption, namely exchange adsorption.

2.3 membrane separation

Membrane separation is a new wastewater treatment technology developed rapidly. Its principle is to put the solution into the membrane filter, to make it through the membrane surface in parallel, in contact with the membrane surface at the same time, most of the solution through the filter membrane, the separation of material was discharging system. 2.4 ion exchange method

Ion exchange method is the use of solid phase ion exchanger functional groups of exchangeable ions, and the contact of the exchanger in the solution of the same electrical ion exchange reaction, in order to achieve the ion replacement, separation removal, enrichment and other purposes.

3 physical

Physical method is based on the principle of physical function, give priority to in order to remove the insoluble solid suspended solids, as well as removing part of biochemical oxygen demand material, reduce and eliminate the effect of wastewater chroma. In papermaking wastewater treatment process, sometimes also used without the use of chemicals and fiber accelerator physics method to remove the solids in the wastewater treatment and recycled fiber, etc., such as air flotation, filtering method and extrusion method, etc.

4 the biochemical method

Biochemical method is the use of microbial degradation metabolism for inorganic organic matter to deal with wastewater. Through the environment to create suitable for microbial survival and reproduction, multiply, in order to improve the efficiency of its oxidative decomposition of organic matter. According to the use of microbial species, can be classified as aerobic, anaerobic and enzymatic.

5 a variety of methods used

Single use some methods for wastewater treatment, not only the cost is high, the waste water after treatment is also difficult to achieve discharge standard, therefore, generally use a variety of methods used in the process of production, the collocation of finding the best way to get a good treatment effect, but also try to reduce the processing cost, and simplify the process.

conclusion

Papermaking wastewater treatment technologies, although there have been many mature at the end of but consider from the Angle of dual economic and environment, the clean production and zero discharge are the ideal process. The traditional wastewater treatment technology is also by continual innovation and development. Each method and technique has its advantages and disadvantages and applicable condition. Generally speaking, the pollutants in wastewater is varied, also have the best processing method, so you can t expect a method to deal with the purpose, several methods are often required to form a processing system, to complete the required effect.