Study On Combination And Mechanism Of Compound Flocculant On Treatment Of HNS Producing Wastewater

HNS is a kind of single component high explosive and possesses excellentcomprehensive properties, so it can be widely used in various fields. The wastewater fromprocessing HNS is industrial organic wastewater with high COD content, toxicity and colority.Although microbial flocculant is efficient, nontoxic and no secondary pollution, its industrialapplications are limited because of low yield and high production cost. In order to promotethe application of bioflocculant in HNS producing wastewater treatment, bioflocculant wasselected to combine with inorganic flocculant to deal with HNS producing wastewater.Composite flocculant was screened by discussing treatment effect of HNS productionwastewater with microbial flocculant that was combined with inorganic flocculant ferricchloride, aluminium chloride and polymeric aluminium chloride. Treatment condition ofcomposite flocculant in HNS producing wastewater was optimizedby using single factorexperiment and response surface analysis test. Mechanism of composite flocculant wasdiscussed in treating wastewater. The main results are as follows:According to the flocculation rate of microbial flocculant for HNS producing wastewater,high-efficient anaerobe bacteria SY-6was screened from four flocculants producing strainswhich had a tolerance to HNS producing wastewater and were obtained by domesticatedincubation of rejuvenated flocculant producing strains with increasing the concentration ofHNS producing wastewater in the culture medium step by step. The optimal cultureconditions for flocculating wastewate was medium initial pH6, the temperature34℃andincubation time60h.When a single flocculant was used to treat wastewater, the removal rates of COD fromhigh to low were microbial flocculant SY-6, polyaluminium chloride, ferric chloride,aluminium chloride, the removal rates for COD were68.21%,54.71%,50.09%and48.04%respectively. When bioflocculant SY-6was combined with three inorganic flocculants respectively totreat wastewater, synergistic effect of bioflocculant SY-6and FeCl₃（AlCl₃） was observed;oppositely, no synergistic effect of bioflocculant SY-6and PAC. The COD removal rates ofthree kinds of combination to wastewater from high to low were FeCl₃/SY-6, AlCl₃/SY-6andPAC/SY-6. Based on the removal rate of COD and the dosing quantity, it was gained that thebest constituent of composite flocculant were FeCl₃and SY-6.By completing single factor experiment and response surface analysis test, it can becertained that the optimal process parameters for composite flocculant were treatmenttemperature20℃, pH5.6, FeCl₃（5%）3.07mL, SY-62.18mL, adding order FeCl₃/SY-6. TheCOD of wastewater under optimal condition decreased to7760mg/L from31200mg/L, thechromaticity decreased to450times from3750times and the removal rates were75.13%and88%respectively.By analysing the contaminant in HNS producing wastewatethe with liquidchromatography and the structure characteristics of the flocculant, the mechanism of thecomposite flocculant to traet HNS production wastewater was explored. It was inferencedpreliminarily that the predominant mechanism of composite flocculant on treatment of HNSproducing wastewater is degradation of anaerobic bacteria and flocculation of compositecoagulant. Flocculation was a result of comprehensive effect of compressing the thickness ofthe electric doublelayer and charge neutralization of ferric chloride and adsorption bridging ofSY-6.When the composite flocculant FeCl₃/SY-6was used to deal with high concentrations ofHNS producing wastewater, the removal rate of COD was superior to the single flocculants.The dosing of flocculant was lower and FeCl₃can be used in place of calcium chloridecoagulant aid, so this treatment technologie can not only reduce processing costs by60%around, but also reduce the residual iron ions in wastewater, it can eventually improve theeconomy and security of the flocculating agent. Composite flocculant is a kind of efficientand low cost flocculating agent which can be used to deal with high concentrations of HNSproducing wastewater. The innovation point of this paper is that flocculants producing strain is the high efficientthalli which screened by the flocculation rate of microbial flocculant for HNS producingwastewater. Using bioflocculant combined with inorganic flocculant ferric chloride to treatHNS producing wastewater, the COD of wastewater is reduced and the biodegradability isimproved. It can provide the theoretical basis and technical support for the treatment ofexplosive wastewater in high concentration and promote industrial application.