| Printing and dyeing wastewater has become one of the difficult processing of industrial wastewater because its refractory organic matter?complex composition?deep chromaticity and high water quality change.At present,there are a lot of printing and dyeing wastewater treatment methods at home and abroad.However,in the practical engineering application,coagulation method is most widely used in dyeing factory,because of its low cost,high efficiency,strong operability,whether in the nanotubes processing phase or standard processing phase.In recent years,industry of printing and dyeing wastewater discharge standard has been improved continuously,and dissolving organic matter in printing and dyeing wastewater are varied and components are complex,including refractory organic matter,the intermediate of organic matter degradation and soluble microbial products.The solubility of organic pollutants in the water greatly affects the behavior of organic matter in the depth subsequent process and after the discharge.So the remnants of soluble organic matter in the printing and dyeing wastewater must be controlled effectively.But conventional coagulation only focused on the removal effect of the particulate matter and colloid in the water.In order to achieve the goal of control of disinfection by-products by removing the soluble organic matter in printing and dyeing wastewater,the United States environmental protection agency?USEPA?recommended strengthening coagulation as a best practical technology.So-called enhanced coagulation,which is by increasing the dosing amount of coagulant or adjust pH value,to improve the removal efficiency of the conventional treatment of residual soluble organic matter for removing the disinfection by-products precursor.Enhanced coagulation experiments were carried out for the treatment of effluent from equalization basin in a centralized printing and dyeing wastewater treatment plant in Wuxi city,Jiangsu province.The enhanced performance using Al2?SO4?3,PFS,FeCl3,PAC,FeSO4,and MgSO4 was studied,to discuss transformation rule of soluble organic matter in wastewater in the process of the enhanced coagulation treatment and various coagulants on the effectiveness of dissolving organic matter in printing and dyeing wastewater treatment.Get the following main conclusions:?1?The molecular weight of raw water mainly focused on two molecular weight range of >100 kDa and < 1 kDa.The proportion of CODcr,UV254 in molecular weight range of > 100 kda are 55.29%,and 36.48%,and in < 1 kda molecular weight range,the proportion are 24.66% and 23.92%.After the enhanced coagulation treatment,macromolecular organic matter removal effect is obvious,and the percentage of small molecule organic matter in water increase dramatically.At the same time,according to SUVA values of coagulation water can show that the enhanced coagulation can achieve the goal of removing hydrophilic substances in the waste water.?2?For the CODcr index,the most effective coagulant is FeCl3 during molecular weight range of 100 kDa > and < 1 kDa.The most effective coagulant is Al2?SO4?3 in the 30-100 kDa,10-30 kDa and 3-10 kDa molecular weight range.For UV254 index,FeSO4 and PFS showed the best effect in > 100 kDa molecular weight range.For 30-100 kDa molecular weight range,Al2?SO4?3 showed the best effect.PFS coagulation on the molecular weight range in the 10-30 kDa and 1-3 kDa in organic matter removal effect is best.In 3-10 kDa and < 1 kDa molecular weight range,FeCl3 showed the best removal efficiency.?3?Hydrophobic neutral content?HoN?and hydrophilic substances?HiM?in raw water accounts for most of the matter,reaching 54.89% and 27.36% respectively.Enhanced coagulation indeed has effect on improving the ratio of hydrophilic or hydrophobic organic matter in the printing and dyeing wastewater.For HoN,CODcr removal rate of FeCl3 coagulation reached 73.6%.For HoA,Al2?SO4?3 on the CODcr removal rate can reach 98.52%.For WHoA and HiM,the PAC are showing the best removal effect.?4?Functional groups on the dissolving organic matter in raw water is primarily a benzene ring,hydroxyl,phenol,ether,ketones,esters,amino and so on.According to the FT-IR and GC-MS spectra analysis result,PFS of removing features to hydroxy coagulation is better than the other three kinds of flocculants.The PAC ability of removing organic matter containing benzene ring is poor.Iron salts on ester?C – O?has a better removal features.?5?Selecting Al2?SO4?3 and PFS as the mixed solution by elemental coagulant of enhanced coagulation experiment result analysis.And determining the best ratio for compound coagulant are Al2?SO4?3 30%?PFS 70% by strengthening coagulation experiments.?6?According to the result of FT-IR,compound coagulant has the better removing features of ester,ether,phenol,alcohol compounds of C-O stretching vibration peak in compared with Al2?SO4?3 and PFS used lonely. |
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