A Study On Advanced Treatment And Decolorization For Paper-making Wastewater By Biologically Activated Carbon

Pulp and paper industry plays an important role in national economy, but papermaking wastewater has the properties of high COD values, deep chroma, high contnent of lignin and the large capacity of drainage, which is the kind of most difficult treatment wastewater. When the wastewater with higher chroma is discharged into environment directly, the landscape will be deteriorated and the aquatic organisms will be died. To develop paper industry, the advanced treatment technology should be researched and applied to engineering practice, which can reduce or even eliminate the damage to the ecology.Bioaugmentation and biological activated carbon(BAC) technique was used in advanced treatment of paper-making wastewater in this paper. Firstly, the optimum technological parameters of hydraulic retention time(HRT), gas-liquid state, strain combination and Activated Carbon types were studied by small scale simulated tests in lab. The testing result showed that HRT was 4 hours, rotation speed was 150r/min, Phanerochaete chryscsporium and Rhodopseudomonas composite stabilizer was good, the particle size of activated carbon is 4-8 Mu.In order to press close to practical engineering application, a pilot scale test which lasted for 100 days was runned in a papermaking wastewater treatment plant of Shandong. Compared to blank control group with the removal rates of COD and chroma were 30% and 40%, the removal rates of COD and chroma increased to 55% and 50% after embarking bacteria, which showed a better treatment effect. The removal rate of chroma reached to 70% and above when high efficency decoloration bacteria group was secondary screened and embarked. During the advanced treatment of papermaking wastewater, it had the effect of simultaneous removal COD and chroma, which suggested that the chromophoric groups in papermaking wastewater made relatively high contributions to COD.Analyzing lots of teat data, it illustrated that when the turbidity was low, there were linear correlation between COD_Cr and chroma of papermaking wastewater with the linear equation was y=2.6792x+42.638 and correlation coefficient(R) was 0.8738, respectively. According to different turbidity of wastewater, a series of modified formulas were derived out. When the turbidity was less than 2 NTU, the organic dissolved molecular with chromophoric groups made relatively high contributions to COD, and COD_Cr could be estimated accurately by the formulation of COD_Cr-Chroma. With the increase of turbidity(more than 2 NTU), the standard deviation of estimated values by formulation had a approximate linear ascending tendency, so two influencing factors: chroma and turbidity should be taken into account. In the lower operation cost, the effluent water after advanced treatment by bioaugmentation technique met and even better than the requirements of papermaking industry effluent discharge standard. This paper confirmed the Water treatment process was feasible by system tests, which provided the valuable theory reference for engineering application.