Research On The Pollution Characteristics And Regular Of DCS In Micro-discharge Of Wastewater From Regenerated Papermaking

With the increasing pressure of the environment, the closed degree of water system becomes higher and higher.The pollutants which are difficult to be removed will accumulate gradually in the system, and they will produce certain negative effects on papermaking process and paper quality. The gradual accumulation of the harmful pollutants are referred to Dissolved and Colloidal Substance, abbreviated as DCS as the dissolution of the papermaking industry.DCS substance is unique in papermaking wastewater which contains large amounts of dissolved and semi-dissolved.DCS substance contains both inorganics and organics, and they are different in chemical and physical nature, which will interfere papermaking and sewage treatment.Based on a typical papermaking enterprise in Zhejiang Province as the research object and this project explored the characteristics of pollution and degradation of DCS substance. There are three points of main work. Firstly, the feature pollutants of DCS substance were screened by analysising the composition of water from the treatment process unit by using gas chromatography mass spectrometry.Secondly, the pollution characteristics parameters and thresholds of DCS substance were determined.Through literature research choiced DCS characteristic parameters. The experiment of pulp and handsheet can simulate paper production, which can help explore the relationship between the number of cycles with the characteristic parameters and performance parameters of paper and determine the critical value of the DCS characteristic parameters. Finally, the pollution laws of DCS substance were proven by examining the distribution characteristics of DCS substance in the water treatment process units and measuring the changes of characteristic parameters of DCS. The pollution trajectories of DCS were established.The results show that the water quality of DCS wastewater treatment process unit is complex. The kinds of organic species reduce from50to20from the ramp gateway to the secondary settling tank, of which there are many materials accumulating and difficult to remove. According to the relative content of organics in DCS wastewater and the difficult of biochemical degradation, etc., myrtenol derivatives, dehydroabietic acid trimethylsilyl ester and bis (trimethylsilyl) alcohol vanilla are screened as the feature pollutants of DCS substance.According to the results of literature survey, size distribution, Zeta potential values, conductivity, cationic demand and COD are selected as the characteristic parameters.The experiment of pulp and handsheet results show:DCS particle size mainly distributes in two regions:100-200nm and200-400nm, among which the number of particle of100-200nm are in the majority. Zeta potential of CS contributes DCS, and the Zeta potential (absolute value) of DCS decreases with the increasing of the number of cycles.The cationic demand of DCS and DS constantly increases with the increasing of the number of cycles, and the cationic demand of DCS is mainly contributed by DS. DS is the main source of electrical conductivity in DCS substance, and the electrical conductivity of DCS and DS increases with the increasing of the number of cycles. The COD of DCS is mainly contributed by DS, and the COD of DCS and DS increases with the increasing of the number of cycles. The content of DCS and DS significantly increases with the increasing of the number of cycles, and the content of DCS is mainly contributed by DS.The performance parameters of paper continuously reduce with the increasing of the number of cycles, and when the number of cycles is more than18, the accumulatetion of DCS substance will produce serious negative impact on paper operations and the performance parameters of paper. At that time, the content of DCS substance reaches3469.59mg/L, the COD of DCS substance reaches985.23mg/L, the Zeta potential of DCS substance reaches-29.90mV, the cationic demand of DCS substance reaches284.30meq/L, the conductivity of DCS substance reaches2.85mS.The particle size distribution of DCS in water treatment process units has two main distribution peaks:0.1～0.2μm and0.2～0.3μm. The peak of ramp gateway and secondary sedimentation tank is0.2Φ0.3～m, and the peak of primary sedimentation tank effluent and R2S reactor is0.1Φ0.2～m. The Zeta potential of DCS is mainly contributed by CS, and the Zeta potentials of primary sedimentation tank and secondary sedimentation tank are both high. The substance is contributed DS mainly, and the cationic demands of DCS and DS increase when treated by R2S reactor.DS is the major conductivity source of DCS, and the contribution of CS is small, and the conductivity of wastewater decrease when treated by water treatment process units.The COD of DCS substance is mainly contributed by DS, and COD reduced obviously when treated by physicochemical and biochemical processes. The content of DCS is mainly contributed by CS, and the contents of DCS and DS both decrease when treated by water treatment process units.