Performance Of Nitritation Adjusted By Chemical Method And The Following Anammox

At present, some new biological nitrogen removal methods, such as simultaneous nitritation and denitritation and anaerobic ammonium oxidation (ANAMMOX) are invented according to the treatment of low C/N wastewaters, which could not be well treated by conventional nitrification and denitrification. Partial nitritation/ANAMMOX has been successfully applied to treat sludge digester liquid, landfill leachate, livestock wastewater and monosodium glutamate wastewater. The key of nitritation and ANAMMOX is to control ammonia oxidation to nitrite but not nitrate. Some control parameters of nitritation, such as medium temperature, pH, alkalinity, HRT and DO, have been successfully used to inhibit ammonia oxidation to nitrite. However, it is difficult to operate through these control parameters, and the nitritation system is seriously influenced by the water quality, organic loading and environmental conditions. Therefore, it is necessary to find an economical, simple, and easy method for the nitritation process, which has important theoretical significance and application value.This article attempts to cultivate nitrosifying granules by chemical method, and simultaneous nitritation and denitritation adjusted by chemical reagent is successfully in the aerobic granular system. Aerobic nitrosifying granules are cultured by dosing NOB-selective inhibitors (chlorate and hydroxylamine). In the SBR, most of the organic matters could be removed, reducing or eliminating the inhibitory effect of organic matters on the ANAMMOX bacteria. Thus, ANAMMOX bacteria and denitrifiers can coupled well for treating of low COD contained wastewaters. Then, a lab-scale nitrosifying granules/ANAMMOX experiment is conducted for the treatment of low ammonia and low C/N wastewaters.In the pilot-scale MBBR, partial nitritation is quickly established with hydroxylamine addition. Then the NOB inhibitor is not added into the MBBR, but nitritation could be well maintained using the other control parameters, such as FA, FNA, SRT and temperature, etc. Most of the biodegradable organics are removed and the effluent nitrite/ammonia ratio is also suitable for the ANAMMOX.Moreover, quick start-up of ANAMMOX is studied in a pilot-scale no-woven RBC, and then it is applied to treat sludge digester liquid. Some innovative findings have been made as follows:(1)Partial nitrification was successfully achieved with addition of5mM chlorate in the aerobic granular system. Chlorate with concentrations ranged from1mM to10mM is beneficial for the nitrite accumulation. This chemical inhibitor selectively inhibited NOB over AOB. FISH analysis revealed that AOB became the dominant nitrifying bacteria, whereas NOB was detected only in low abundance. During stable partial nitrification, the influent pH was kept at7.8-8.2, while the DO and temperature were not controlled in the SBR. When the NH4+-N and COD levels were kept at100mg/l and400mg/1in the influent, the NH4+-N and COD removal efficiencies reached99%and79%, respectively. The NO2--N accounted for93%of the NOx--N (NO2--N+NO3--N) in the effluent. Furthermore, about90%of the chlorate was reduced to nontoxic chloride, thus it would not cause environmental problem.(2)Simultaneous nitritation and denitritation was successfully achieved by hydroxylamine dosing, and it just took3weeks to start up a pilot nitritation reactor. Nitrite accumulation was quickly detected after10mg/L hydroxylamine addition, treating synthetic wastewater containing100mg/1NH4+-N and400mg/1COD under conditions of room temperature ad pH7.8-8.2. TN removal efficiency was57%with a NO2--N/NO-X-N ratio of99.8%. Meanwhile,79%COD was removed by aerobic granules. SEM detection showed that the main composition of aerobic granules was coccus and bacilli bacteria. FISH results indicated that AOB were the dominant bacteria of aerobic granules.(3)Heterotrophic denitrifying bacteria were competitive with ANAMMOX bacteria for the NO2--N in the simultaneous ANAMMOX and denitritation. When the COD/NO2--N decreased to1.9, and NO2--N/NH4+-N was2:1, NO2--N, NH4+-N, COD and TN removal efficiencies reached93%,96%,87%and94%, respectively. ANAMMOX was the main reaction.(4)Results shows ANAMMOX reaction was quickly detected with little ANAMMOX seed sludge in the non-woven rotating biological contactor (NRBC), under the conditions of temperature18～25℃, pH7.0. During the first90days, the TN removal rate reached about1kg·N·m-3·d-1. The color of ANAMMOX biofilm changed from pale yellow to dark red, with a biomass improvement of20folds. Clone library analysis of HZO gene and16S rRNA showed that ANAMMOX bacteria in the pilot RBC were mainly composed of Candidatus Jettenia, Candidatus Brocadia. Then the NRBC was applied to treat digester liquid, and the results demonstrated that it had feasibility to remove nitrogen from high-ammonia wastewater by ANAMMOX.