Tatsuo Sumino

Nitrogen removal performance using anaerobic ammonium oxidation at low temperatures

An anaerobic ammonium oxidation (anammox) process for ammonia-rich wastewater treatment has not been reported at temperatures below 15 degrees C. This study used a gel carrier with entrapped anammox bacteria to obtain a stable nitrogen removal performance at low temperatures. In a continuous feeding test, a high nitrogen conversion rate (6.2 kg N m(-3) day(-1)) was confirmed at 32 degrees C. Nitrogen removal activity decreased gradually with decreasing operation temperature; however, it still occurred at 6 degrees C. Nitrogen conversion rates at 22 and 6.3 degrees C were 2.8 and 0.36 kg N m(-3) day(-1), respectively. Moreover, the stability of anammox activity below 20 degrees C was confirmed for more than 130 days. In batch experiments, anammox gel carriers were characterized with respect to temperature. The optimum temperature for anammox bacteria was found to be 37 degrees C. Furthermore, it was clear that the temperature dependence changed at about 28 degrees C. The apparent activation energy in the temperature range from 22 to 28 degrees C was calculated as 93 kJ mol(-1), and that in the range from 28 to 37 degrees C was 33 kJ mol(-1). This value agrees with the result of a continuous feeding test (94 kJ mol(-1), between 6 and 22 degrees C). The nitrogen removal performance demonstrated at the low temperatures used in this study will open the door for the application of anammox processes to many types of industrial wastewater treatment.

Immobilization of nitrifying bacteria by polyethylene glycol prepolymer

Abstract The effects of immobilizing materials on the activity of nitrifying bacteria were investigated by using 11 kinds of prepolymers of polyethylene glycol. Relative respiratory activity of immobilized nitrifying bacteria with polyethylene glycol metacrylate prepolymer was higher than that of polyethylene glycol acrylate prepolymer, and there was a tendency for relative respiratory activity to be higher with a prepolymer of greater molecular weight. With the polyethylene glycol prepolymer, there was a drastic improvement over the conventional method of immobilization by acrylamide in the relative respiratory activity of the pellet. Inorganic synthetic wastewater was treated under a high loading rate of 1.14 kg-N/m 3 ·d. Influent NH 4 -N could be removed to 2 mg/ l or less and the nitrogen removal was 90%.

Innovative treatment system for digester liquor using anammox process.

This study demonstrated that partial nitritation using nitrifying activated sludge entrapped in a polyethylene glycol (PEG) gel carrier, as a pretreatment to anammox process, could be successfully applied to digester liquor of biogas plant at a nitrogen loading rate of 3.0 kg-N/m(3)/d. The nitritation process produced an effluent with a NO(2)-N/NH(4)-N ratio between 1.0 and 1.4, which was found to be suitable for the subsequent anammox process. A high SS concentration (2000-3000 mg/l) in the digester liquor did not affect partial nitritation treatment performances. Effluent from this partial nitritation reactor was successfully treated in the anammox reactor using anammox sludge entrapped in the PEG gel carrier with T-N removal rates of greater than 4.0 kg-N/m(3)/d. Influent BOD and SS contents did not inhibit anammox activity of the anammox gel carrier. The combination of partial nitritation and anammox reactors using PEG entrapped nitrifying and anammox bacteria was shown to be effective for the removal of high concentration ammonium in the digester liquor of a biogas plant.

Immobilization of nitrifying bacteria in porous pellets of urethane gel for removal of ammonium nitrogen from waste-water

SummaryThe effects of immobilizing materials on the activity of nitrifying bacteria and removal of ammonium nitrogen (NH4-N) from waste-water by immobilized nitrifying bacteria were investigated using six urethane prepolymers. With a urethane prepolymer containing 2.27% free isocyanate, a high activity yield of nitrifying bacteria was obtained. There was a drastic improvement over the conventional method of immobilization by acrylamide in the activity yield. Inorganic synthetic waste-water was treated at a high loading rate of 0.24 kg N·m−3·day−1. The NH4-N concentration of the effluent could be reduced to 2 mg·1−1 or less and the removal was 90%. The life of the pellets in terms of activity was at least 120 days.

Microbial diversity of anammox bacteria enriched from different types of seed sludge in an anaerobic continuous-feeding cultivation reactor.

Enrichment of anammox bacteria from three types of seed sludge, sewage, digester, and nitrification sludges, was conducted using a nonwoven fabric carrier for immobilizing the anammox bacteria, and the microbial diversity of the enriched anammox culture was investigated. About four months later, simultaneous removals of ammonium and nitrite, and production of a small amount of nitrate, which is unique to the anammox reaction, were observed in all 3 sludge reactors. Results of 16S rRNA gene analysis indicated that anammox bacteria were cultivated and diversified in each sludge type. Moreover, the microbial diversity of anammox bacteria was higher in the enriched culture from sewage sludge compared to the other two types of seed sludge. Bacillus sp. coexisted in the anammox culture cultivated from sewage sludge. These results suggest that differences in the anammox community in the enriched culture were caused by differences in the type of seed sludge.

Wastewater treatment using activated sludge entrapped in polyethylene glycol prepolymer

Abstract Immobilized activated sludge was applied to the treatment of organic wastewater discharged from a semiconductor plant. To enhance the treatment efficiency, the growth characteristics of heterotrophic bacteria and the effect of the BOD loading rate in continuous wastewater treatment by the immobilized activated sludge were investigated. The activated sludge was entrapped in polyethylene glycol (PEG) prepolymer pellets. Wastewater with a BOD of 150–200 mg/l was continously treated in a 200-l capacity prototype reactor. The effluent BOD concentration after treatment was 10 mg/l or less at a loading rate of a 5.21 kg-BOD/m3·d, representing BOD removal of 95–97%. The layer of heterotrophic bacteria in a pellet was 300 μm in depth, which was thicker than that of immobilized nitrifying bacteria fed on domestic wastewater.

Immobilization of activated sludge by the acrylamide method

Abstract A new method for the effective immobilization of activated sludge using acrylamide was developed. Viable counts of Gram-negative bacteria dominant in the activated sludge were reduced by an immobilizing preparation, while those of Gram-positive bacteria were not. To protect activated sludge from the toxicity of the immobilizing agent, it was coagulated with a coagulant agent (Praestol 444K) to obtain primary particles, and these were immobilized in acrylamide. The respiration rate of immobilized microorganism pellets produced by the new method was 3 to 15 times that of conventional immobilized pellets.

Microbial community of anammox bacteria immobilized in polyethylene glycol gel carrier

Anaerobic ammonium oxidation (anammox) is a recently discovered microbial pathway in the biological nitrogen cycle and a new cost-effective way to remove ammonium from wastewater. We have so far developed new immobilization technique that anammox bacteria entrapped in polyethylene glycol (PEG) gel carrier. However, fate and behavior of anammox bacteria in a gel carrier is not well understood. In the present study, we focused on the population changes of anammox bacteria in a gel carrier. Three specific primer sets were designed for real-time PCR. For quantification of anammox bacteria in a gel carrier, real-time PCR was performed. The anammox bacteria related to HPT-WU-N03 clone were increased the rate in anammox population, and found to be a major population of anammox bacteria in a gel carrier. Furthermore, from the results of nitrogen removal performance and quantification of anammox bacteria, the correlation coefficient between copy numbers of anammox bacteria and nitrogen conversion rate was calculated as 0.947 in total anammox population. This is the first report that population changes of anammox bacteria immobilized in a gel carrier were evaluated.