| Wastewater from the traditional Chinese medicine (TCM) production is one of high concentration organic wastewater with complicated composition and bigger fluctuation of water quality and quantity. In addition, TCM is a kind of intractable wastewater with poor biochemical and bigger toxicity. In general, wastewater is very difficult to reach discharge standard with a single traditional biological treatment. Therefore, a certain pretreatment technology is needed to guarantee effluent to be up to the discharge standard, with reducing the organic load and biological toxicity of wastewater and improving the biodegradability of wastewater. Based on the present application situation of pretreating TCM wastewater with coagulation, this paper investigated the pretreatment of coagulation sedimentation process and optimized the parameters of coagulation sedimentation process. In addition, removal mechanism of particular pollutants in TCM wastewater with coagulant was studied.Based on the analysis of wastewater composition, the polyaluminium chloride (PAC), aluminium sulfate (AS) and polyacrylamide (PAM) were selected as the coagulant in the treatment of TCM wastewater. Three types of coagulant were mixed to treat TCM wastewater. Coagulation experiment showed that the best proportion of three kinds of coagulants was PAC:AS:PAM=3:2:1. Determined by single factor experiment and response surface experiment, when the coagulant dosage, velocity gradient, mixing time and sedimentation time was50mg/L,41.4s-1,17.1min and50.1min, respectively, the highest COD and SS removal efficiency of process for TCM wastewater was acquired(19.15%and73.43%,respectively), which providing a theoretical guidance for the practical engineering application.The coagulation precipitation reactor pilot running results show that the running effect of coagulation sedimentation process was stable, the removal rate of SS, chroma, COD and toxicity was60%~70%,70%,20%, and4%~7%, respectively. Coagulation sedimentation process has a positive impact to the running effect of whole process, the B/C of coagulation effluent increased to more than0.35. Compared with single biochemical treatment process, COD removal rate of coagulation+biochemical treatment process increased about10%. The coagulation process could reduce the toxicity of wastewater; wastewater toxicity removal rate of coagulation+biochemical treatment process could reach10%. Coagulation process played a role of pretreatment in wastewater treatment, and created favorable conditions for the subsequent biological treatment.In this paper, poly aluminium chloride (PAC) was used to remove phenol and aniline from the aqueous phase.The adsorption properties of this process was investigated by Zeta potential measurement, infrared spectroscopy and scanning electron microscopy. The results described that not only electrostatic attraction but hydrogen adsorption were the main mechanism of both the phenol adsorption and the aniline adsorption. The reasonable inference of these two adsorption processes was shown as below: phenol and aniline adsorbed on the floc in the mode of reaction of hydrogen bonding or electrostatic, followed by an adsorption process that used H+as charge-balancing ions. All above constituted a molecular adsorption. However, different structure and chemical properties of phenol and aniline combined with the Zeta potential measurement revealed that the adsorption between PAC and aniline is stronger.The results of adsorption kinetics research of phenol and aniline described that the pseudo second-order kinetic equation could best describe these two adsorption kinetics, the adsorption process were both chemisorption. Friedrich model was fitter to describe the adsorption isotherm of these two adsorption processes. |
PDF Full Text Request