Research On The Technology Of Removing Nitrogen And Phosphorus Of Co-processing Pickle Organic Wastewater With High Concentration Of Salt And Nitrogen And Municipal Sewage

With the rapid economy development of the Three Gorges Reservoir, the level ofintensive producing of its pillar business pickle is getting higher, the scale is gettinglarger and larger,therefore organic wastewater with high concentration of salt andnitrogen and phosphorus from pickle producing enterprises has increased year by year.According to the requirement of environmental control, the pickle wastewater is treatedby producing enterprises to reach the third class criteria of Integrated WastewaterDischarge Standard (GB8978-1996) by anaerobic treatment and is drained intomunicipal wastewater sewer to be treated by municipal wastewater plants. Though thewastewater has reached the aim of environmental control(COD＜500mg/L, SS＜400mg/L), it becomes to be other kind of water with low concentration ofcarbon(COD=200~500mg/L), high concentration of nitrogen (TN=200~280mg/L), highconcentration of phosphorus(TP=25~40mg/L) and high concentration of salt(NaCl=20~35g/L). For a long time, municipal wastewater plants are effected by thiskind of pickle wastewater tailrace with high salt, low C/N ratio and low C/P ratio, as aresult, the treatment efficiency of wastewater is poor especially the removal of nitrogenand phosphorus，as a result of serious excess concentrations of pollutants.To realize the aim that the effluent of municipal wastewater plants that inceptedpickle wastewater tailrace could reach the first B class discharge standards of “CitiesSewage Treatment Plant Pollutant Discharged Standard”(GB18918-2002), and startingwith salt resistance properties of activated sludge in the system of co-processing picklewastewater and municipal wastewater, it’s studied on the limited salt resistance ofactivated sludge in the processing system of municipal wastewater. Against theproblems of low C/N ratio, poor biological nitrogen removal, high influent phosphorusconcentration and the limited biological phosphorus removal of co-processing system,the research was performed on strengthened biological nitrogen removal andbiological-chemical phosphorus removal, which received running parameters,established running mode of biological nitrogen removal on the condition of low carbonsource and phosphorus removal model with different phosphorus removing agents andanalyzed the effect of phosphorus removing agents on activated sludge. The resultswould provide technology support and scientific evidence for co-processing pickleorganic wastewater with high concentration of salt and nitrogen and municipal sewage and the productive experiment. The main research contents and results were as thefollows:①Research on salt resistance running properties of the processing system ofmunicipal wastewater.The activity of dehydrogenase was the evaluation of salt resistance properties ofactivated sludge. In the processing system of municipal wastewater adding5%picklewastewater tailrace, it’s discovered that the more the salinity was, the lower both theactivity of dehydrogenase of activated sludge and the processing efficiency were. Whensalinity arose from1g/L to10g/L, the activity of dehydrogenase decreased from4.83μgTF/mgMLSS·h to4.13μgTF/mgMLSS·h, and the system could realize thedischarge of COD, NH4+-N, TN and SS meet the standards. When the salinity washigher than10g/L, the activity of dehydrogenase reduced obviously and the treatmentefficiency of wastewater was poor especially the removal of nitrogen and phosphorus.At the same time, it’s discovered that the higher the salinity was, the lower sludge yieldcoefficient was, which had effect on biological phosphorus removal in the processingsystem of municipal wastewater. When the salinity was higher than5g/L, the coefficientof sludge yield ratio was lower than0.3kgMLVSS/kgBOD, the efficiency of biologicalphosphorus removal was poor, chemical phosphorus removal was needed to meetphosphorus discharge standards.By deeply studying on the effect of salinity on settleability of activated sludge, it’sdiscovered that the higher the salinity was, the better settleability of activated sludgewas in the processing system of municipal wastewater, but it had bad effect on SS ofeffluent. When the salinity arose from1g/L to10g/L, the settleability exponent ofactivated sludge SVI decreased from108mL/g to78mL/g and SS of effluent arose from5mg/L to19mg/L, the salinity concussion could change the settleability of activatedsludge in activated sludge micro-bulking system, when the concussion was less than thesalinity of primary processing system, SVI arose and caused sludge bulking; when theconcussion was more than the salinity of primary processing system, SVI decreased andrestrained sludge bulking.②Research on nitrogen removal in the system of co-processing pickle wastewatertailrace and municipal sewage.Under the conditions of not adding carbon source, the C/N ratio that met biologicalnitrogen removal under low carbon source was taken as the needed carbon source ofbiological nitrogen removal in co-processing system of pickle wastewater tailrace and municipal wastewater. By using methanol and pickle wastewater as carbon source toimprove the dosing ratio of pickle wastewater tailrace in the co-processing system, it’sanalyzed about biological nitrogen removal. The results showed that without addingcarbon source and under the conditions that the ratio of adding pickle wastewatertailrace was5%~10%and the salinity was1.2g/L~2.5g/L, when the range of C/N was4.5~5.0, biological nitrogen removal could be realized and COD, NH4+-N and TN of theco-processing effluent could meet the first B class discharge standards (GB18918-2002). By using methanol and pickle wastewater as carbon source separately tocontrol the C/N ratio between4.5and5, the ratio of pickle wastewater tailrace could beraised to25%and20%separately in the co-processing system, and biological nitrogenremoval and COD removal could be realized efficiently belong the ratio of picklewastewater tailrace, and COD, NH4+-N and TN of the co-processing effluent could meetthe first B class discharge standards (GB18918-2002).It’s also studied on the effect of C/N ratio, salinity and carbon source on nitrogenremoval of co-processing, the results showed that when C/N was3:1, NO2-–N wasliable to be gathered in the system of co-processing, TN removal was low and TN ineffluent couldn’t meet the standard, when C/N was4:1and5:1, the efficiency of TNremoval got well in the co-processing system and TN removal rate was more than70%.When the salinity was within6.5g/L, the higher the salinity was, the higher the gatheredratio of NO2-–N and so was specific denitrification rate of the system were, The arisingdenitrification rate behaved as removing nitrogen by NO2-–N denitrification. ByComparing nitrogen removal efficiencies in the co-processing system with methanoland pickle wastewater as carbon source, it showed that using pickle wastewater ascarbon source of co-processing pickle wastewater tailrace and municipal sewage openedup a new way of choosing carbon sources achieving the purpose of treating wastewaterwith wastes.③Research on biological phosphorus removal and on biological-chemicalphosphorus removal in the co-processing system.By analyzing biological phosphorus removal of co-processing system according tosludge yield ratio, it’s discovered that the higher the salinity was, the lower the sludgeyield ratio in co-processing system was, and biological phosphorus removal waseffected by the sludge yield ratio. Without adding carbon source, when the ratio ofpickle wastewater tailrace was5%~10%, the salinity of mixed inffluent was1.2g/L~2.5g/L, the coefficient of sludge yield ratio was0.33~0.35, the TP of effluent could meet the standard by biological phosphorus removal in the co-processing systemand TP removal rate was82.2%~84.3%. When adding methanol and pickle wastewaterseparately as carbon source and the ratio of pickle wastewater tailrace was11%~15%,the salinity of mixed inffluent was3.5g/L~4.0g/L and4.0g/L~4.5g/L separately, theaverage coefficient of sludge yield ratio was0.32and0.30, the TP of effluent couldmeet the standard by biological phosphorus removal in the co-processing system and TPremoval rate was81.1%~78.7%separately. When the ratio of pickle wastewater tailracewas more than15%, the salinity of mixed inffluent was more than4.0g/L, thecoefficient of sludge yield ratio was less than0.30, the TP of effluent couldn’t meet thestandard by biological phosphorus removal in the co-processing system, which neededchemical phosphorus to realize TP standard.Against the problems that the influent TP concentration was high in co-processingsystem under high ratios of pickle wastewater tailrace and biological phosphorusremoval couldn’t meet the standard, the research was performed on strengthenedbiological-chemical phosphorus removal when the ratio was20%with methanol ascarbon source and on the effect of phosphorus removing agents on activate sludge. Theresults showed that dosing different phosphorus removing agents according to the ratioof the concentration of amount of substance of the metal ion in phosphorus removingagents and influent TP, phosphorus removal regularity of effluent TP concentration anddosing ratios of different phosphorus removing agents was discovered:(1)FeCl3,y=5.466e-2.38x(R~2=0.998);(2)Al2(SO4)3, y=5.539e-2.00x(R~2=0.990);(3)polymeric ferricsilicate, y=5.060e-3.06x(R~2=0.977); The effect of phosphorus removal was polymericferric silicate> FeCl3> Al2(SO4)3; Dosing phosphorus removing agents could reduceCOD and SS effluent concentration, enhance settleability of activated sludge andimprove sludge floc structure, dosing aluminum salts was better than dosing ferric saltsand polymeric ferric silicate was best. Dosing polymeric ferric silicate and FeCl3hadlittle effect on OUR and the activity of dehydrogenase of activated sludge. The effect ofAl2(SO4)3on OUR of denitrifying bacteria was stronger than that of nitrifying bacteriaand heterotrophic bacteria, while the activity of dehydrogenase hadn’t been reduced bydosing Al2(SO4)3.④The productive experiment of co-processing pickle wastewater tailrace andmunicipal wastewater.According to the situation of pickle wastewater tailrace flowing into a municipalwastewater processing plant in a town of the Three Gorges Reservoir and combining studying results of the trials, the productive experiment was carried out aboutco-processing pickle wastewater tailrace and municipal wastewater in the wastewaterprocessing plant. It’s discovered that during the productive experiment running inOctober2011to June2012, in the two cases that the ratios of pickle wastewater tailracewere9%~10%and12%~13%, and that not adding carbon source and adding methanolas carbon source separately to raise C/N ratio to4.5~5,and the dosage was65~70mLmethanol per cubic foot water, the effluent of productive experiment could reach thefirst B class discharge standards (GB18918-2002). During the productive experimentrunning in July2012to August2012, when the ratio of pickle wastewater tailrace were20%, C/N ratio of inffluent was less than3, methanol was added as carbon source andthe dosage was108~117mL methanol per cubic foot water, biological-chemicalphosphorus removal was carried out together by dosing polymeric chloride one hourbefore stopping aeration, carbon source was added to raise C/N ratio to4.5:1~5:1, andthe dosage of polymeric chloride was15g/m~3, the effluent of productive experimentcould reach the first B class discharge standards (GB18918-2002).The results of research on the technology of removing nitrogen and phosphorus ofco-processing pickle organic wastewater with high concentrations of salt and nitrogenand phosphorus with municipal sewage would provide scientific evidence andtechnology support for scale of engineering practices, and it’s of important realisticsignificance.