Study On Treatment Technology And Technology Of Lacre Processing Wastewater

Lac is a kind of forest product owning high economic value, and also an important industrial raw material. A wide application were existed in food, medicine, household chemicals, paints and many other areas. Lac processing obtains mainly product including particulate lac and bleaching lac, meanwhile large amounts of sewage are generated in this process. Especially generating sewage has a greater harm in the process of washing and bleaching. In LAC processing process of the rubber particles, will produce Lac washing wastewater, leading a series of pollution question following great color, perception difference and high COD value. In the typical process of bleached shellac, it is difficult to effectively collect by conventional filtration or clarification way, failure to collect the particles will liquid into the sewage with washing water, resulting in a higher value of suspended solids, COD and BOD in sewage. Natural sedimentation and coagulation sedimentation often used in the current practice of shellac bleaching wastewater treatment.Few experimental studies were reported in the present study. Flocculation and advanced oxidation technology, and then combined with the biochemical treatment way were commonly used. Some disadvantages were existed such as long time consuming, high cost, and poor practicability and so on.In view of the above, appropriate test programs were made combined with the characteristics of the wastewater. Some sedimentation agents were selected to dispose Lac washing waste-water which was cheap and easy to get from market such as iron salt, aluminum salt, calcium salt and its oxides, etc. A kind of sedimentation agent were screened out for further process which has better treatment effect and lower cost. According to the characteristics of the shellac bleaching waste-water the thermal coagulation was selected to treat them. The suspended solids in the waste-water were aggregation, settling, separating and recycling by this method. Thereby suspended solids concentration and subsequent processing load were reduced, and a good foundation for the further processing were provided by this method. Then UV-Fenton oxidation was used for further process which has wide application range and strong oxidation characteristics. After treatment Lac processing waste-water was reached the effluent discharge standards emission targets. The main research contents and results were as follows:1、Under the conditions of the different pH and dosages, six kinds of sedimentation agent were selected to explore the effect of reducing the chrominance value. Finally, CaO was selected as the optimum sedimentation agent by the experimental result, and optimized its sedimentation process through using response surface methodology. Meanwhile the optimum experimental conditions can be obtained such as dosage of 5.7g/L, reaction temperature of 50℃ and stirring rate of 270r/min. The value of chromatic value, CODCr, BOD, total nitrogen and total phosphorus in the sample decreased respectively from 2125,4019mg/L,3800mg/L,75.6mg/L and 25mg/L to 70,853mg/L,680mg/L,30.8mg/L and 13mg/L after sedimentation treatment. The total anthraquinone content for the Lac washing wastewater before and after CaO treatment was detected. In addition, elemental analysis and GC-MS were tested to prove it. CaO as sedimentation agent to reduce the content of organic substances containing shellac color acid was further evidenced. It showed that the method was simple, affordable and practical.2、In order to reduce the COD value of Lac washing waste-water, the UV-Fenton oxidation method was used for further treatment. The effects of H2O2 concentration, FeSO4 concentration, reaction time and initial pH value were studied on COD removal efficiency. The optimum conditions of UV-Fenton oxidation treatment of Lac washing waste-water were obtained through the Design-Expert design. Meanwhile the optimum experimental conditions can be obtained such as The H2O2 dosage of 13.7g/L, the FeSO4 dosage of 0.6g/L, the reaction time of 2h. The value of CODCr and BOD in the sample decreased respectively from 853 mg/L,670 mg/L to 107 mg/L,57mg/L after the thermal coagulation treatment. They were reached the secondary effluent discharge standards emission targets. In this process, accompanied by the COD value reduced, the suspended solids, chroma, total nitrogen and total phosphorus also were reduced. The value of total nitrogen and total phosphorus in the sample decreased respectively from 30.8mg/L and 13mg/L to 0.055mg/L and 0.074mg/L. Which were reached the secondary effluent discharge standards emission targets.3、This work describes a simple and effective pretreatment process. It can ease the subsequent processing burden and reduce suspended organic solids in bleached shellac wastewater by the thermal coagulation method. The methods of single factor and the response surface are used for this experiment. Meanwhile the optimum experimental conditions can be obtained such as reaction temperature of 55 ℃, thermostatic time of 130min and stirring rate of 80r/min. The value of suspended solids, turbidity, CODCr and BOD in the sample decreased respectively from 1489mg/L,1689NTU,4735.6mg/L and 2460mg/L to 237.6mg/L,420NTU, 2280.8mg/L and 1640mg/L after the thermal coagulation treatment. The principle of coagulation by characterizing the structure, properties and morphology of suspended solids in the sample is proposed preliminarily in this article. There are two processes about the phenomenon of thermal coagulation. The two process includes the softening aggregation and the contraction settlement. The softening is the basis of aggregation of shellac solids. And the contraction is the reason of settlement of shellac solids. So it concludes that the thermal coagulation of the shellac solids related to the effect of the two processes above.4、In order to reduce the COD value of bleached shellac wastewater, the UV-Fenton oxidation method was used for further treatment. The effects of H2O2 concentration, FeSO4 concentration, reaction time and initial pH value were studied on COD removal efficiency. The optimum conditions of UV-Fenton oxidation treatment of bleached shellac wastewater were obtained through the Design-Expert design. Meanwhile the optimum experimental conditions can be obtained such as The H2O2 dosage of 49g/L the FeSO4 dosage of 2.6g/L, the reaction time of 4h. The value of CODcr and BOD in the sample decreased respectively from 1938mg/L,1169mg/L to 48mg/L,32mg/L after the thermal coagulation treatment. They were reached the secondary effluent discharge standards emission targets. In this process, accompanied by the COD value reduced, the suspended solids, chroma, total nitrogen and total phosphorus also were reduced. Which were reached the secondary effluent discharge standards emission targets.The results showed that the lac washing wastewater treatment through two steps which were flocculation method and UV-Fenton oxidation method. The value of chromatic value, CODcr, BOD, total nitrogenand total phosphorus in the sample decreased respectively from 2125,4019mg/L,3800mg/L,75.6mg/L,25mg/L to30, 107mg/L,57mg/L,0.055mg/L, and 0.074mg/L after the treatment. All of them were reachedthe secondary effluent discharge standards emission targets. After the thermal coagulation and UV-Fenton oxidation method, the value of COD, BOD chromatic value, suspended solids, total nitrogen and total phosphorus in the bleached shellac wastewater decreased respectively from 4735mg/L,2460mg/L,112, 1489mg/L,3.06mg/L,0.47mg/L to 48mg/L,32mg/L,24mg/L,27.3mg/L,0.027mg/L and 0.021mg/L after the treatment.All of them were reached the secondary effluent discharge standards emission targets.