| The water quality of food waste fermentation wastewater is complex,with the characteristics of low C/N ratio,high ammonia nitrogen concentration and organic matter concentration,and containing difficult-to-biodegradable organic matter.If the traditional nitrification and denitrification technology is used to treat the water,the energy consumption is high,the amount of additional carbon source is large,and the treatment cost is high.The short-cut nitrification-anaerobic ammonia oxidation,a new nitrogen removal combined process,has the advantages of no need to add a carbon source,saving aeration,and being economical and efficient.However,because anammox is a process in which a certain ratio(1:1.32)of ammonia nitrogen and nitrous nitrogen reacts,short-cut nitrification can obtain a relatively stable ammonia/nitrous nitrogen effluent through artificial control,which is difficult to control.In view of the characteristics of food waste fermentation wastewater,this study proposed pre-anaerobic UASB(carbon removal and heterotrophic denitrification)-complete short-cut nitrification(SBR)-anaerobic ammonia oxidation(the generated nitrate nitrogen is returned to the pre-anaerobic UASB)combined process to treat this type of water.Compared with partial short-cut nitrification-annamox process,the combined process is easier to obtain stable and matrix proportion of annamox influent water quality(after pre-anaerobic UASB carbon removal,part of the effluent crosses the short-cut nitrification and enters the annamox unit),which is conducive to annamox nitrogen removal.;At the same time,each reaction unit runs in sections.None of the three reactors requires sludge reflux.Sludge is stored in the respective reactor,so this method allows different functional strains(heterotrophic bacteria,autotrophic bacteria)to play their respective advantages under their own appropriate conditions,and avoids sludge backflow to other units to affect the system.In addition,the pre-anaerobic UASB can perform heterotrophic denitrification and nitrogen removal while removing organic matter,which further improves the TN removal efficiency of the combined process.The main conclusions obtained are as follows:(1)The pre-anaerobic UASB was inoculated with anaerobic granular sludge,and it was started by diluting the raw water in stages under the conditions of a temperature of30°C and an HRT of 48 hours.Subsequently,the HRT was shortened to increase the processing capacity of the reactor.After 79 days of operation,under the conditions of 12hours of HRT and a volume load of 10.03 kg COD/(m3·d),the COD removal rate of food waste fermentation wastewater was maintained at about 79%.The nitrogen in the effluent is mainly NH4+-N,which meets the demand for subsequent anaerobic ammonia oxidation denitrification.(2)Inoculation of aerobic nitrification sludge in SBR,under the conditions of low oxygen,high temperature and low influent ammonia nitrogen concentration,after 17cycles,the rapid start of short-cut nitrification was realized.After the system is connected to the pre-anaerobic UASB effluent,the NH4+-N removal rate can be maintained by reducing the treated water volume and extending the aeration time.After the short-cut nitrification effect is stable,when the influent NH4+-N concentration is1139?1157 mg/L,the NH4+-N removal rate is 94.10%,and the NO2--N accumulation rate is 92.78%.(3)The mixed sludge of anaerobic granular sludge and anammox sludge was inoculated in the anammox reactor,and the start of anammox was realized after 89 days under the condition of low nitrogen load with artificial water distribution.Then gradually increase the concentration of NH4+-N and NO2--N in the influent to 450 mg/L and 594 mg/L,and the removal rates of NH4+-N and NO2--N reached 92.58%and92.93%,respectively.In the short-cut nitrification effluent process,the reaction system has the best denitrification effect when the HRT was 6h.The removal rates of NH4+-N and NO2--N were 96.94%and 93.00%,respectively,the TN removal rate was 82.23%,and the TN removal load was 3.366 kg N/(m3·d).The ratio of NH4+-N removal,NO2--N removal,and NO3--N production was 1:1.27:0.21.When the denitrification effect of the system is good,the p H of the effluent will increase.(4)The pre-anaerobic-short-cut nitrification-annamox combined process has a good removal effect on most of the easily biodegradable organic matter in the food waste fermentation wastewater.The effluent COD concentration is 889?900mg/L,and the COD removal rate was about 82%.The TN in wastewater was mainly removed by anaerobic ammonia oxidation reactor(approximately 91.6%of total removal)and pre-anaerobic reactor(approximately 7.1%of total removal).The combined process has a TN removal rate of 84.05%.The average concentrations of NH4+-N,NO2--N,and NO3--N in the combined process effluent are 17.20mg/L,43.13mg/L and 135.33mg/L,respectively.Then optimize the pre-anaerobic UASB effluent water volume in the combined process.When the current anaerobic effluent volume accounts for 37%of the anaerobic ammonia oxidation water volume,the combined process has the best denitrification performance and the TN removal rate is about 87.62%. |
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