A kind of treatment process of leather-making waste water
One, technical field
The present invention relates to a kind of method of wastewater treatment, specifically a kind of treatment process of leather-making waste water.
Two, background technology
According to statistics, annual global ox-hide, sheepskin, about 8,000,000 t of pigskin turnout, annual tanning industry will reach more than 8,000 ten thousand t to environmental emission waste water in China, accounts for 0.3% of China's industrial wastewater discharge total amount; Ten thousand yuan of output value blowdown flow rates of leather industry occupy the 3rd at light industry, are only second to papermaking and brewing industry.Contain poisonous, objectionable impuritiess such as amounts of protein, fat, inorganic salts, suspended substance, sulfide, chromium and vegetable tanning agent in the leather-making waste water, biochemical oxygen demand (BOD) height, toxicity are big.In addition, the time of the tanning industry sewage whole day discharging water yield is very inhomogeneous, and instantaneity is strong, and the sewage quality of each workshop section's discharging differs greatly, and therefore causes the impact load of tanning sewage water quality, the water yield all very big.The characteristics of leather-making waste water are brought very big difficulty to waste water control.It is reported that the discharging of leather-making waste water has caused groundwater pollution, therefore, treatment of Tannery Wastewater is seemed particularly important.
The waste water quality of each workshop section discharging differs greatly in the process hides process, the composite waste pH after the waste water of each workshop section's discharging compiles between 8-12, colourity, COD
Cr, SS, BOD
5Concentration is all very high, poisonous, the concentration of objectionable impurities and salt is also very high.Table 1 is a leather industry composite waste water quality situation.
Table 1 leather industry composite waste water quality (testing mean) (unit: all the other are mg/L except that pH, colourity)
pH |
Colourity (doubly) |
COD
Cr |
SS |
NH
3-N
|
S
2- |
Cl
- |
BOD
5 |
8-12 |
600-3500 |
3000-4000 |
2000-4000 |
250-300 |
50-100 |
2000-3000 |
1500-2000 |
At present, be used for the method that leather-making waste water administers and mainly contain: coagulant sedimentation, absorption method, high-level oxidation technology, directly loop back usage, air supporting method, add sour absorption process, catalytic oxidation, biochemical process etc., every kind of method all has various relative merits.Be specially:
(1), coagulant sedimentation
This method is by the pH value of adjustment waste water and the parameters such as dosage of coagulating agent, can realize the removal to pollutent in the waste water at normal temperatures, but coagulant sedimentation also has the shortcoming of self, the pH value of regulating waste water needs to consume a large amount of soda acids, simultaneously, the saltiness of waste water is raise.
(2), absorption method
This method can realize the absorption to most of pollutent in the waste water, and adsorption effect is not subjected to the influence of inorganic salt, but absorption later sorbent material be difficult to resolve again, and loading capacity is little, increases running cost in the practical application.
(3), high-level oxidation technology
High-level oxidation technology processing waste water can make the oxidation operation in the waste water, can improve the biodegradability of waste water simultaneously, but various high-level oxidation technology energy consumption height in application process, and be subjected to influence of various factors, few in actual applications.
(4), directly loop back usage
Be generally used for the reuse of chromium in the leather-making waste water, the chrome liquor that will give up combines in liquid storage tank after using the thickness grid filtration, analyzes various substances content, and adjusting pH value back directly circulation is used for pickling and just tans.This method also consumes a large amount of soda acids, and simultaneously, the chromium of reuse influences the quality of leather.Common and the additive method coupling of this method.
(5), air supporting method
Be generally used for the processing of oil wastewater in the leather-making waste water, air-blast device blasts air by aerating apparatus in waste water, and the bubble that air forms in water takes the oils in the water to water surface, reaches the purpose of oily water separation.Common and the additive method coupling of this method.
(6), add sour absorption process
Be generally used for the processing of sulfur-containing waste water in the leather-making waste water, this method is under condition of negative pressure, adds the sulphur acid for adjusting pH value to 5-6 in depilation liming waste water, and the sulfide in the waste liquid generates hydrogen sulfide, absorb the back with sodium hydroxide and generate sodium sulphite, sodium sulphite is recyclable to be used again.This method consumes a large amount of sulfuric acid to the equipment requirements height, and is higher to equipment corrosion.Common and the additive method coupling of this method.
(7), catalytic oxidation
Be generally used for the processing of sulfur-containing waste water in the leather-making waste water, this method is to be catalyzer with the manganous sulfate, and air is blasted in the sulfur-containing waste water, makes the sulphur oxidation generate thiosulphate and vitriol, to reach innoxious purpose.Common and the additive method coupling of this method.
(8), biochemical process
Biochemical process comprises anaerobic process and aerobic method; The anaerobic process floor space is big, and the cycle of operation is long, and energy consumption is relatively low, and it is less to produce sludge quantity, and the aerobic method cycle of operation is short, and energy consumption is bigger, and it is more to produce sludge quantity.Handle leather-making waste water with biochemical process and will carry out pre-treatment to waste water usually, reduce poisonous, objectionable impurities toxic side effect microorganism.
In sum; existing method is not to have cost height, complicated operation; there are a series of problems such as bring secondary pollution easily, be difficult to apply exactly,, are beneficial to protect environment so be badly in need of the new method of wastewater treatment of low, simple to operate easy, the non-secondary pollution of a kind of cost.
Three, summary of the invention
The objective of the invention is at the poor processing effect that exists in the existing leather-making waste water treatment technology, one-time investment height, consume shortcoming such as a large amount of chemical agents, provide that a kind of clearance height, technology are simple, the method for pollutent in the removal leather-making waste water of non-secondary pollution.
The alleged leather-making waste water of the present invention is meant the composite waste that compiles each workshop section's discharging, and the technical scheme of its processing comprises electrolysis and separates.Described electrolysis is exactly that leather-making waste water two the placed in-line electrolyzers of flowing through successively carry out electrolysis, and being provided with the stainless steel in first electrolyzer is the pole plate of electrode, and being provided with the aluminium sheet in second electrolyzer is the pole plate of electrode.
Experiment showed, before electrolysis treatment, waste water is carried out oxide treatment earlier, and then carry out electrolysis treatment and can improve processing efficiency.
The oxygenant that described oxide treatment is used is selected from clorox or sodium chlorate or hydrogen peroxide, and add-on is 0.05~0.1mol/L.Preferred clorox or sodium chlorate.
Experiment is proof also, and the spacing in current density when treatment effect and electrolysis and the electrolyzer between two adjacent plates (positive and negative electrode) is closely related.Two adjacent polar plate spacings are controlled between 10~20mm in the electrolyzer, and the current density during electrolysis is 40~60mA/cm
2In two electrolyzers, the spacing of two adjacent stainless steel polar plates can equate with the spacing of two adjacent aluminum substrates, also can be unequal, but the variation range of spacing is 10~20mm.Current density during two electrolytic tank electrolysis is as the same, promptly can be identical current density, or selects current density separately, but the variation range of current density is 40~60mA/cm
2
The flow through size (battery lead plate what) of flow velocity with electrolyzer of electrolyzer of waste water is relevant during electrolysis treatment, and the big person's flow velocity of electrolyzer can be quicker, instead then slow a bit, should regulate and control according to last result.
The present invention utilizes electrolytic process that leather-making waste water is handled, and contains a large amount of salts (mainly being sodium-chlor) in the leather-making waste water, and the conductivity of waste water is fine, can reduce electrolysis energy consumption.When leather-making waste water flows through the electrolyzer of stainless steel electrode, the stainless steel electrode dissolving, series of physical, chemical reaction take place, sulfide in the waste water is converted into the compound of sulphur and iron, sexavalent chrome in the waste water is converted into the trivalent chromium that chemical property is stable, toxicity is lower, removes partial organic substances simultaneously; When leather-making waste water flow through the electrolyzer of aluminium electrode, series of physical, chemical reaction took place in the dissolving of aluminium electrode, produced electricity flocculation, electric floating effect simultaneously, can remove suspended substance and organism; When removing pollutent, electrolysis also has germicidal action.The more important thing is that the ammonia nitrogen in high density that contains in the leather-making waste water is insoluble problem always, electrolysis in the present invention has higher removal efficient to the ammonia nitrogen in the waste water.By precipitation the flocs unit that produces in the electrolytic process is precipitated at last, can reach the purpose of removing multiple pollutent in the leather-making waste water by said process.
The invention provides a kind of treatment process of brand-new leather-making waste water, electrolysis treatment all has good effect of removing to the organism in the waste water, ammonia nitrogen, sulfide, suspended substance, colourity, have germicidal action simultaneously concurrently, waste water COD clearance after the processing reaches 60-80%, ammonia nitrogen removal frank and reaches that 50-70%, sulfide clearance reach more than 95%, the suspended substance removal rate reaches 70-80%, chroma removal rate reaches more than 85%, and colibacillary killing rate is reached more than 99%.
Electrolytic process is handled relative other method of leather-making waste water and is had the following advantages:
(1) can be by changing impressed current conditioned reaction condition at any time, controllability is stronger;
(2) organic pollutant that issuable free radical does not have in selectively direct and the waste water in the process reacts, and it is degraded to carbonic acid gas, water and simple organic;
(3) reaction conditions gentleness, electrochemical process generally just can be carried out at normal temperatures and pressures;
(4) reactor apparatus and operate fairly simple;
(5) have air supporting, throwing out concurrently.
Four, description of drawings
Fig. 1 is a leather-making waste water electrolysis treatment process flow diagram.I is the stainless steel polar plate electrolyzer, and II is the aluminum substrate electrolyzer.
Fig. 2 is the electrolyzer orthographic plan.
Fig. 3 is an electrolyzer A-A sectional view.
Fig. 4 is an electrolyzer B-B sectional view.
Five, embodiment
Below in conjunction with accompanying drawing, non-limiting examples is described below.
Shown in Fig. 1,2,3,4.
Get stainless steel plate and aluminium sheet processing pole plate 1, pole plate 1 holds swinging seat 2 by plastics and is separately positioned among placed in-line electrolyzer I and the II, two adjacent polar plate spacing 15mm.
The bottom of electrolyzer I and II is provided with bucket 3, the collecting precipitation thing, and the one side is provided with scum silica frost receiving tank 5, and scum silica frost flows in the receiving tank from the scum silica frost outlet 4 that upper part of the electrolytic cell is provided with.Scum silica frost outlet and entery and delivery port position are consistent.
Working process of the present invention is:
Electrode pad in the electrolyzer is connected constant voltage dc source according to positive and negative electrode mode at interval, make waste water flow through respectively successively two the electrolyzer I and the II of stainless steel, aluminium electrode; Connect power supply, regulate the current density 50mA/cm of constant voltage dc source
2, leather-making waste water is carried out the two-stage electrolysis; Because the throw out that electric throwing out produces enters bucket,, the scum silica frost that electric floating effect produces draws in the electrolytic process because exporting from scum silica frost.Again the waste water after the above-mentioned electrolysis treatment is precipitated and get final product.