Study On Improving The Performance Of White Water Recycling By Microorganism And Enzyme

Recycling of papermaking white watercan not only save the use of fresh water,but also can reduce the loss of fiber and chemicals,reduce production costs,in the protection of the environment,energy conservation and other aspects also have important significance.However,with the increase of water circulation,the harmful substances in white water will gradually accumulate.Among these harmful substances,the most influential chemical effects on papermaking and papermaking wetting are the dissolved and colloidal substances(DCS).DCS is the main source of anionic waste.DCS in the paper machine system continues to accumulate,which requires the addition of more cationic additives to neutralize,the processing costs are getting higher and higher,while increasing the organic emissions of follow-up wastewater,increasing the difficulty of wastewater treatment.Biological method is paid more and more attention in the field of wastewater treatment because of its economy and environmental protection.To this end,this experiment uses biological technology to deal with DCS water,improve its processing performance.First of all,the white water of papermaking was pretreated,and the DCS water was obtained by 20 min under the condition of 2000r/min.The physical and chemical properties of papermaking white water and DCS water were analyzed.The cation demand(CD)of papermaking white water and DCS water were 510?s / cm and 425?s / cm,respectively.The conductivity was 1894?s / cm and 1926?s / cm,respectively.Oxygen content(CODcr)were 1320 mg / L and 950 mg / L,pH values were 7.64 and 6.94 respectively,the content of DCS in papermaking white water was 3.4475 g / L,and the content of CS in DCS was 1.2380 g / L.And the microbial growth curve method was used to measure the respiration curve and the biochemical respiration curve of DCS.The results showed that the biodegradability of DCS water was good.Secondly,because the microorganisms in the middle section of the pulping waste water are used as the living environment of the polysaccharides,lignin and resin in the raw materials,it is suitable to grow and deal with these substances.These substances are also present in the white water and are easy to enrich,and become a part of the formation of anionic waste water.Therefore,the dominant strains were screened from the waste water from pulping,and the strains were purified,identified and expanded.Finally,two kinds of dominant strains were identified,which were Brevundimonas-diminuta and Virgibacillus-pantothenticus.Thirdly,with the pH as the variable,the growth curve of the two microorganisms under different pH conditions and the change of CODcr in the effluent of the middle section of the pulp were measured to determine the optimum pH of the microbial growth.Then the temperature was taken as the variable to measure the removal rate of CODcr from the two kinds of microorganisms in different pulping temperature.The optimum pH=5 of two kinds of microorganisms was determined by experiment,and the optimum growth temperature was 30?.Finally,the effects of microbial and enzyme preparation treatment on the recovery of DCS water were discussed by using the dominant bacteria from the separation and purification of the pulp in the middle of the pulp and using the dominant bacteria and the enzyme to deal with the DCS water.The best treatment of DCS water was determined when the dosage of Pseudomonas aeruginosa and Pseudomonas aeruginosa was 1: 2.And when the immobilized pectinase compound,immobilized pectinase added increasing processing efficiency more quickly,however,the amount of enzyme increases will inevitably lead to increased processing costs,the application should choose according to the amount of enzyme preparation.