Study On The Treatment Technology Of Waste Cutting Fluid From Machine Industry

With the rapid development of China's industrial enterprises,the consumption of cutting fluids in the machining industry has been increasing,resulting in a large number of hazardous solid waste-waste cutting fluids.The waste cutting fluid is a kind of high concentration organic waste liquid,which is difficult to degrade because of its complex composition,stable property and poor biodegradability.In this paper,the waste cutting fluid of a company in Qingdao was used as the research object.The purification treatment was carried out by coagulation demulsification,Fenton oxidation and SBR.The coagulation effects of PAC,PFS and FeCl₃ coagulants were examined by selecting CODcr and petroleum as the evaluation indexes.The preparation formula of FeCl₃ was optimized,and then the direct SBR biological treatment of coagulation supernatant and the SBR biological treatment after Fenton oxidation were studied,the process parameters of Fenton oxidation were optimized,and the sludge load of SBR method was determined,so as to provide reference for the process selection and design parameters of the actual waste cutting fluid treatment project.The main results are as follows:?1?The removal efficiency of FeCl₃ to CODcr and petroleum is better than that of PAC and PFS in the pretreatment of waste cutting fluid by coagulation process,adopt secondary coagulation treatment,the optimal dosage was 2.0 g/L for the first level and 0.5 g/L for the second level.The total removal rates of CODcr and petroleum were 89.0% and 98.6% respectively.The concentrations of CODcr and petroleum decreased from 31300mg/L and 4951mg/L to 3400mg/L and 68.8 mg/L.?2?The research on the influence of the proportion of Fe²⁺ residue on the coagulation effect in the preparation of FeCl₃ shows that when FeCl₃ was prepared by FeCl₂ with an initial concentration of 25%.when the Fe²⁺ residue is 32.5%,the coagulation effect of FeCl₃ can be achieved.Therefore,the amount of oxidant and stabilizer can be saved and the preparation cost can be saved.The best removal rates of CODcr and petroleum can reach 59.0% and 94.7% respectively.?3?Fenton oxidation method was used to treat the supernatant of coagulation and sedimentation.The results of orthogonal test showed that the primary and secondary order of the factors was: H₂O₂ dosage>n H₂O₂:n Fe²⁺>p H> reaction time.According to the primary and secondary sequence of single factor optimization test,the optimal parameters are: 0.058 mol/L of H₂O₂,n H₂O₂:n Fe²⁺=5:1,90 min of reaction time and 3 of p H adjustment.Under this condition,the CODcr concentration of the effluent is 934 mg/L and the removal rate is 72.4%.Petroleum is not detected.In addition,the infrared spectrum analysis shows that the coagulation method and Fenton oxidation method can effectively remove the oil in the waste liquid,and the chlorinated paraffin which is difficult to degrade can be removed by Fenton oxidation.?4?When the supernatant of coagulation and sedimentation is directly treated by SBR process,the sludge load can be increased to 0.24 kg CODcr/kg MLSS·d,the CODcr concentration of effluent water can be stabilized at 260 mg/L,the removal rate of CODcr is about 92.0%,and the removal rate of petroleum is 0.6 mg/L.The sludge load of SBR process can be increased by adding domestic sewage,which can reach 0.36 kg CODcr/kg MLSS·d.at the same time,the concentration of CODcr can be stabilized at about 230 mg/L,and the removal rate of CODcr is about 92.0%.The effluent quality of CODcr and oil of both processes can meet the grade C standard in Table 1 of Wastewater quality standards for discharge to municipal sewers?GB / T 31962-2015?.Adding domestic sewage into the supernatant of coagulation sedimentation can improve the biochemical treatment efficiency,but the final removal rate of CODcr is not improved,which shows that the supernatant of coagulation sedimentation contains non biochemical degradation components,limiting the final removal rate.In view of the effluent of coagulation precipitation supernatant,after Fenton oxidation,the sludge load of SBR process can be increased to 0.6 kg CODcr/kg MLSS·d,the concentration of CODcr is stable at about 45.0mg/l,the removal rate of CODCr is about 95.0%,the oil is not detected,the effluent quality of process CODcr and oil can meet the first level discharge standard of integrated wastewater discharge standard?GB 8978-1996?.Fenton oxidation treatment can oxidize the refractory macromolecules in the supernatant of coagulation sedimentation into the easily biodegradable micromolecules,and the biodegradability of the waste liquid is greatly improved.For the Fenton oxidation test of the system effluent directly treated by SBR process,under the best conditions,when the dosage of Fenton reagent is 0.0116 mol/L for H₂O₂ and 0.0023 mol/L for Fe²⁺,the CODcr concentration of the oxidized effluent is 103mg/L,and the effluent quality is not as good as that of Fenton+SBR process.Therefore,when the effluent quality requirements are high,Fenton+SBR process should be used for the supernatant of coagulation sedimentation.?5?Bacterial diversity analysis of three kinds of activated sludge was carried out according to Illumina miseq high-throughput sequencing.The dominant phylum are Proteobacteria and Bacteroidetes.The dominant phylum are Proteobacteria and Bacteroidetes,in which the proportion of Proteobacteria and Bacteroidetes in the activated sludge of direct SBR process is 53.68% and 21.07% respectively,the proportion of Proteobacteria and Bacteroidetes in the activated sludge of Fenton+SBR process is 32.17% and 60.07% respectively,the proportion of Proteobacteria and Bacteroidetes in the activated sludge of coagulation supernatant+10% domestic sewage+SBR process is 52.04% and 27.88% respectively.