ABSTRACT
Catching bed biofilm reactor combined with traditional biofilm process as a novel treatment was developed. The performance of the reactor for nitrogen removal was investigated. Steady removal effect with 81.7% of average COD removal rate was achieved in various hydraulic retention time (HRT). Even when hydraulic retention time (HRT) was only at 3.90 h with average NH4(+) -N volumetric loading of 0.47 kg/(m3 x d) and TN of 0.59 kg/(m3 x d), 92.7% of average NH4(+) -N removal rate and 67.5% of average TN removal rate were achieved. In the experiment dissolved oxygen (DO) was the most crucial factor for removal rates of TN and pH was a crucial factor for removal rates of NH4(+) -N, TN. The optimal condition was with DO 0.1-2.0 mg/L and pH of 7.0-7.5. Mechanisms of TN removal via simultaneous nitrification and denitrification in the experiment were analyzed.
Subject(s)
Biofilms , Bioreactors/microbiology , Nitrogen/isolation & purification , Waste Disposal, Fluid/methods , Denitrification , Nitrification , Nitrogen/metabolism , Organic Chemicals/isolation & purification , Organic Chemicals/metabolism , Quaternary Ammonium Compounds/isolation & purification , Quaternary Ammonium Compounds/metabolismABSTRACT
This study evaluated performance of swim-bed (SB) reactors packed with a novel acrylic fiber carrier (BF) and swim-bed activated sludge (SBAS) reactor for partial nitritation of anaerobic sludge digester liquor from a municipal wastewater treatment plant. Comparison of characteristics of sludge obtained from both the reactors was also made. The average conversion rates of ammonium to nitrite were 52.3% and 40.0% under relatively high nitrogen loading rates over 3.0 kg-N/m(3)/d, respectively in two reactors. The average BOD(5) removal efficiencies were 74.3% and 64.4%, respectively in the two reactors. The size of the sludge pellets taken from SB and SBAS reactors was found to be approximately three times (229 mum versus 88 mum) of that of the seed sludge. This sludge also had relatively high extracellular proteins levels indicating better sludge settling capability as compared to the sludge taken from SBAS reactor. Although the effluent nitrite/ammonium ratios had fluctuated in both reactor in some extent, the low dissolved oxygen concentration (average of 2.5 versus 0.35 mg/l), low suspended solids (average of 33.3 versus 33.5 mg/l), and about 50% ammonium conversion to nitrite demonstrated the application potential of anammox process for nitrogen removal.
Subject(s)
Nitrites/metabolism , Nitrogen/metabolism , Refuse Disposal/methods , Bacteria, Anaerobic , Biomass , Equipment Design , Hydrogen-Ion Concentration , Models, Chemical , Nitrites/chemistry , Nitrogen/chemistry , Oxygen/chemistry , Quaternary Ammonium Compounds/analysis , Quaternary Ammonium Compounds/chemistry , Sewage , Temperature , Time Factors , Waste Disposal, FluidABSTRACT
Partial nitritation using inhibition of free ammonia and free nitric acid is an effective technique for the treatment of high concentrations of ammonium in wastewaters. This technique was applied to the digester liquor of swine wastewater and the stability of its long-term operation was investigated. Partial nitritation was successfully maintained at a nitrogen loading rate (NLR) of 1.0 kg N m(-3)d(-1) for 120 days without acclimatization of nitrite oxidizing bacteria (NOB) to the inhibitory compounds (free ammonia and free nitric acid). The conversion efficiencies of NH(4)-N to NO(2)-N and to NO(3)-N were determined to be around 58% and <5%, respectively. After the establishment of partial nitritation, the influence of swine wastewater on the Anammox reaction was examined using continuous flow treatment experiments. Consistent nitrogen removal was achieved for 70 days at a nitrogen removal rate (NRR) of 0.22 kg N m(-3)d(-1) and the color of Anammox bacteria changed from red to greyish black. The NO(2)-N consumption and the NO(3)-N production increased concurrently and the Anammox reaction ratio was estimated to be 1:1.67:0.53, which is different from that reported previously (1:1.32:0.26).
Subject(s)
Environmental Restoration and Remediation/methods , Industrial Waste , Nitrates/chemistry , Animals , SwineABSTRACT
A swim-bed reactor using the biofringe acryl-fiber biomass carrier was used for partial nitritation treatment for anaerobic digestion liquor of swine wastewater. The sludge in the reactor demonstrated excellent settling properties, and the sludge volumetric index (SVI) was always about 50 ml g(-1). The mixed liquor suspended solids (MLSS) concentration was maintained above 10,000 mg l(-1) with a maximum of 16,800 mg l(-1). Satisfactory and stable partial nitritation was obtained at a nitrogen loading rate (NLR) of 1.9 kg-N m(-3) d(-1) without any operational control. Only a little nitrate was produced almost during the whole operational period and the nitrite to total oxidized nitrogen ratio (NO(2)-N/(NO(2)-N+NO(3)-N)) was always above 95%. In addition, the influence of temperature on partial nitritation efficiencies was also investigated and non-controlled efficiencies were maintained stably between 15 degrees C and 30 degrees C at an NLR of 1.9 kg-N m(-3) d(-1), but suddenly deteriorated when the temperature fell below 15 degrees C. Nitrite oxidizing bacteria were inhibited by free ammonia and free nitric acid, which prevented the conversion of nitrite to nitrate and the inhibition due to free nitric acid weaken with a decrease in temperature. It was apparent that these phenomena were crucial to the control of partial nitritation treatment.
