Study On Treatment Technology Of High-concentration Water-based Coating Wastewater

In this thesis,three coating water wastewaters from a coating company are studied as the target.The three streams of wastewater have the characteristics of high concentration,refractory degradation,many suspended substances and poor biodegradability.If the water are directly emissioned,it can cause great harm to the environment.Considering the wastewater quality and quantity,and the effluent standard,the combined process of "Demulsification treatment-Fenton/ozone advanced oxidation pretreatment-SBR biochemical treatment" was proposed to treat there three wastewaters.Through the process of laboratory research,to derive the optimal wastewater treatment methods meeting the effluent quality standard of the factory and have the lowest treatment cost.Taking No.1 water as the research object,the quality indicators of wastewater main are:concentration of COD 78.0×103mg/L,concentration of BOD5 9.9×103mg/L,concentration of TN 2.1×103mg/L,concentration of TP 22.0mg/L,respectively.Sulfuric acid demulsification was used as the pretreatment process of the wastewater.Under the condition that the concentrated H2SO4 dosage was 2.90L/m3,the COD in the effluent was reduced from 78.0×103mg/L to 17.8×103mg/L,the removal efficiency reached 77.2%,and the turbidity was 5.4NTU.Afterward,the acidified and demulsified supernatant is treated by the ozone oxidation,the COD in the wastewater can be further reduced to 13.3×103mg/L,and the B/C can be increased from 0.12 to 0.37,which are favorable for subsequent biological treatment.The best treatment conditions are:the initial pH of the wastewater is 9.0,the ozone concentration is 30mg/L at the flow rate of 2.5L/min,and the reaction time is 40 min.Effluent after ozone oxidation as inflow of a biochemical pool.After Acclimation and vaccination,the indicators of wastewater effluent are:COD=450mg/L,NH3-N=8.4mg/L,TP=0.90mg/L under the condition of HRT=2d,DO=3.0-4.0mg/L,volume load is 1.22 kgCOD/(m3·d),this time on the removal rate of COD,NH3-N,TP are 60%?65%,85%?90%,90%?95%.The effluent can meet the water quality standard for flushing water in the "Urban Wastewater Recycling and Urban Miscellaneous Water Quality"(GB/T 18920-2002).The effluent is reused directly,which has achieved better social and economic benefits.Taking No.2 water as the research object,the quality indicators of wastewater main are:concentration of COD 118.8×103mg/L,concentration of BOD5 15.5×103mg/L,concentration of TN 12.4×103mg/L,concentration of TP 35.0mg/L,respectively.Sulfuric acid demulsification was used as the pretreatment process of the wastewater.Through the screening of demulsifies,it is determined that PAFC is the optimal demulsifier.Under the condition that the PAFC dosage was 4.0kg/m3 and the initial pH of the wastewater was 6.0,the COD in the effluent was reduced from 118.8×103mg/L to 57.2×103mg/L,the removal efficiency reached 52.0%,and the turbidity was 94.0NTU.Afterward,the demulsified supernatant was treated by the ozone oxidation,the COD in the wastewater can be further reduced to 47.7×103 mg/L,and the B/C can be increased from 0.13 to 0.41,which are favorable for subsequent biological treatment.The best treatment conditions are:the initial pH of the wastewater is 9.0,the ozone concentration is 30mg/L at the flow rate of 2.5L/min,and the reaction time is 120min.Effluent after ozone oxidation as inflow of a biochemical pool.After Acclimation and vaccination,the indicators of wastewater effluent are:COD=425mg/L,NH3-N=8.8mg/L,TP=0.85mg/L under the condition of HRT=5d,DO=3.0?4.0mg/L,volume load is 1.58kgCOD/(m3·d),this time on the removal rate of COD,NH3-N,TP are 70%?75%,85%?90%,92%?95%.The effluent can meet the local pipe discharge water quality standard required by the factory.Taking No.3 water as the research object,the quality indicators of wastewater main are:concentration of COD 99.7×103mg/L,concentration of BOD5 11.9×103mg/L,concentration of TN 10.6×103mg/L,concentration of TP 22.0mg/L,respectively.Sulfuric acid demulsification was used as the pretreatment process of the wastewater.Through the screening of demulsifies,it is determined that PAFC is the optimal demulsifier.Under the condition that the PAFC dosage was 4.0kg/m3 and the initial pH of the wastewater was 6.0,the COD in the effluent was reduced from 118.8×103mg/L to 57.2×103mg/L,the removal efficiency reached 52.0%,and the turbidity was 94.0NTU.Afterward,the demulsified supernatant was treated by the Fenton oxidation,the COD in the wastewater can be further reduced to 34.8×103mg/L,and the B/C can be increased from 0.12 to 0.28.The optimal treatment conditions are:the initial pH of the wastewater is 3.0,the dosage of FeSO4·7H2× is 14.0kg/m3,the dosage of 30%H2O2 is 157.5L/m3,and the reaction time is 8h.Effluent after Fenton oxidation as inflow of a biochemical pool.After Acclimation and vaccination,the indicators of wastewater effluent are:COD=400mg/L,NH3-N=8.9mg/L,TP=0.80mg/L under the condition of HRT=4d,DO=3.0-4.0mg/L,volume load is 1.32kgCOD/(m3·d),this time on the removal rate of COD,NH3-N,TP are 68%?72%,85%?90%,92%?95%.The effluent can meet the local pipe discharge water quality standard required by the factory.After the joint operation of "Demulsification sedimentation-Ozone/Fenton oxidation-SBR biochemical treatment",the effluent quality indicators of the three streams of wastewater were stable and all reached discharge or reuse standards,proving the feasibility of this technical route.