Study On Optimizing Control Technology Of Co-processing Municipal Sewage And Organic Wastewater With High Concentration Of Salt And Nitrogen

Pickle producing is the characteristic and pillar industry of the Three Gorges, butthe waste water treatment rate of the pickle enterprises all over the Three Gorges is lessthan1percent, and the effluent can’t reach drainage standard with the restricted factorof the less of treatment technology for pickle wastewater with high efficiency and lowcost. The results of the earlier experimental research and theoretical analysis showedthat anaerobic treatment and then co-processing with domestic wastewater was anadvisable technique line for the pickle wastewater treatment. However, there were twotechnical bottleneck during the co-processing after anaerobic treatment of picklewastewater: the first was to decide doping amounts of pickle comprehensive wastewaterin result that the effluent of the domestic wastewater treatment system could meet thedischarging standard; the second was to solve the problem of the poor removalefficiency of TN because of the lack of carbon source when co-processing organicwastewater with high concentration of salt and nitrogen and municipal sewage when the picklewastewater was drained into municipal pipes which contained low carbon and highnitrogen after the pickle wastewater reached the third class criteria of IntegratedWastewater Discharge Standard by anaerobic treatment. Therefore, the research wascarried out on co-processing organic wastewater with high concentration of salt andnitrogen and municipal sewage both by the process pilot-scale experiment and by thedemo project. The main research contents and results were as the follows:①The co-processing pilot-scale reactor was started up by inoculating excess slugefrom a domestic wastewater plant and increasing salinity gradually. When operating thereactor under the operation condition that the operating time was8h, drainage ratio was20%, recycle ratio was50%and setting five different ratios （1%,2%,3%,4%,5%） ofadding pickle wastewater to increase the ratio of adding pickle wastewater gradually,DO was controled between2and4mg/L and MLSS was controled about3000mg/L inaeration zone, the reactor worked steadily after start-up25days and the quality ofeffluent could meet the first B class discharge standards of “Cities Sewage TreatmentPlant Pollutant Discharged Standard”（GB18918-2002）.②At the initial stage of reator start-up，the addition of pickle wastewater made thesalinity in the system rising abruptly, which had inhibited the activity of microorganismand caused lysing phenomenon of some microorganism cells. Therefore the removal rates were reduced shortly at the initial stage, about continuing5days and then theremoval rates were increased5days later. Otherwise, it’s discovered that the effluentconcentrations of COD, NH₄⁺_-N, TN, TP and SS were reduced and the removal rateswere increased with the ratio of adding pickle wastewater increased gradually during thereactor start-up. The effluent concentrations of COD, NH₄⁺_-N, TN, TP and SS werereduced to meet the first B class discharge standards of “Cities Sewage Treatment PlantPollutant Discharged Standard”（GB18918-2002） steadily as the microorganism wereadatped to the wastewater qulity.③Under the conditions of not adding carbon source and the low ratio of addingpickle wastewater by single-factor experiments, it’s proved that the optimal operationcondition of co-processing organic wastewater with high concentration of salt andnitrogen and municipal sewage by CASS process were: the operating time was8h,drainage ratio was30%, recycle ratio was100%, under which condition the removalrates of pullants were quite high. The limited ratio of adding pickle comprehensivewastewater was10%without adding carbon source. All qulity index of theco-processing effluent could meet the first B class discharge standards of “CitiesSewage Treatment Plant Pollutant Discharged Standard”（GB18918-2002） within thelimited ratio.④When the ratio of adding pickle comprehensive wastewater was higher than10%, the influent C/N ratio of co-processing was without adding carbon source, theremoval efficiency became worse. The ratio of adding pickle comprehensive wastewatercould improved by adding pickle wastewater or methanol as carbon source to keep theC/N ratio about5:1. The limited ratios of adding pickle comprehensive wastewater was25%with methanol as carbon source and20%with pickle wastewater as carbon source.Within the limited ratios, the qulity index of the co-processing effluent except TP couldmeet the first B class discharge standards of “Cities Sewage Treatment Plant PollutantDischarged Standard”（GB18918-2002） within the limited ratio.⑤By running the demo project under the conditions of admiting picklewastewater at the off season and the peak season of producing pickle pickle wastewater,it’s discovered that the ratio of adding pickle comprehensive wastewater was5%¹0%at the off season and10%¹5%at the peak season. When the operation conditions ofrunning the demo project were: the operating time was8h, drainage ratio was30%,MLSS was2500mg/L³000mg/L and the recycle ratio were100%and150%, the demoproject had high removal rates and all qulity index of the co-processing effluent could meet the first B class discharge standards of “Cities Sewage Treatment Plant PollutantDischarged Standard”（GB18918-2002） within the limited ratio.⑥By contrasting the conditions of adding pickle comprehensive wastewater or not,it was concluded that ajusting the inffluent time （2.5h before adding pickle wastewaterand5h after adding pickle wastewater） and the recycle ratio （100%before and100%and150%after）, the demo project could admit5%¹0%pickle comprehensivewastewater at the off season and10%¹5%pickle comprehensive wastewater at thepeak season, and made the co-processing effluent steady and could meet the first B classdischarge standards of “Cities Sewage Treatment Plant Pollutant DischargedStandard”（GB18918-2002）.By the CASS process pilot-scale experiment of co-processing organic wastewaterwith high concentration of salt and nitrogen and municipal sewage, the limited ratios ofadding pickle comprehensive wastewater were worked out under the conditions ofadding methanol and adding pickle wastewater in result that the effluent of the domesticwastewater treatment system could meet the discharging standard. The results could beused to control the co-processing demo project and would provide technology supportfor selecting the carbon source in the future.