Development of Anammox Reactor Equipped with a Degassing Membrane to Improve Biomass Retention

In up-flow anammox reactors, one of the contributing factors of biomass wash-out is the adherence of nitrogen gas produced by anammox reaction to biomass. In this study, we operated an up-flow anammox reactor equipped with a degassing membrane to minimize the biomass wash-out from the reactor by separating the produced gas from the biomass. In addition, both the effect of degassing on the anammox reactor performance and the durability of the membrane submerged in the anammox reactor were investigated. The results show that the use of the degassing membrane in the anammox reactor could 1) Improve the biomass retention ability (by separating the produced gas from the biomass), and 2) Increase the component ratio of anammox bacteria in the reactor. In addition, degassing could reduce the N2O emission produced in the reactor (for the gas selectivity of the degassing membrane). No membrane fouling was observed even after two months of operation without washing, indicating an advantage to the use of the degassing membrane

ハウス栽培植物の新害虫チビクロバネキノコバエについて(農学部門)

近年, 京都市及び安城市で, ハウス栽培植物(ユリとキュウリ)の根部を食害するハエ幼虫による被害が問題になっている。両地で採集された標本を調査したところ, 本害虫はクロバネキノコバエ科の新種であったので, チビクロバネキノコバエBradysia agrestis Sasakawaと命名し, ここに記載したほか, 2・3の生態的知見を述べる。成虫の寿命は雄で約6日間, 雌は産卵後間もなく死亡するので約4日である。雄は翅を振動させながら雌に接近し, 生殖器の交接後は互に逆方向を向いて数分間交尾する。雌は通常25卵くらいの卵塊を腐植物の裏側に2∿3塊に分けて産みつける。親雌は個体によって雌雄いずれかの単性を産み, その比は1 : 1である。幼虫はトウモロコシ寒天培地での人工飼育が可能であるが, 種々のそ菜の葉や根も摂食することを確かめた。幼虫は4令を経過して蛹化する。理論的発育零点は卵で5.8℃, 幼虫では9.0℃, 蛹では8.7℃であり, 卵から蛹期までの発育有効積算温度は193.1日度である。A new sciarid pest, Bradysia agrestis Sasakawa, is described. The occurrence of this fly has become increasingly troublesome in the plastic houses in Kyoto and Anjyo, Aichi Pref. The larvae infest the roots of potted lily and cucumber in these areas. The investigations on biology have been carried out under laboratory conditions by using Corn Meal Agar media. Preoviposition period is 2-3 days. Females die soon after they have oviposited in a batch of about 25 (20-40) eggs. Males survive about 2 days longer than females. This species is monogenic. Copulation last usually from 3 to 6 minutes. Total number of eggs laid by a single female varies 15 to 110 (average 60-80 eggs). The larvae pass through four instars. Under constant temperatures the developmental periods decreased as temperatures increased from 20 to 28℃. The thresholds of development for egg, larva and pupa are 5.8,9.0 and 8.7℃, respectively, and the thermal constant throughout the immature stage is 193.1 day-degrees

Enhancement of organic matter degradation and methane gas production of anaerobic granular sludge by degasification of dissolved hydrogen gas

A hollow fiber degassing membrane (DM) was applied to enhance organic matter degradation and methane gas production of anaerobic granular sludge process by reducing the dissolved hydrogen gas (D-H2) concentration in the liquid phase. DM was installed in the bench-scale anaerobic granular sludge reactors and D-H2 was removed through DM using a vacuum pump. Degasification improved the organic matter degradation efficiency to 79% while the efficiency was 62% without degasification at 12,000 mg L-1 of the influent T-COD concentration. Measurement of D-H2 concentrations in the liquid phase confirmed that D-H2 was removed by degasification. Furthermore, the effect of acetate concentrations on the organic matter degradation efficiency was investigated. At acetate concentrations above 3 g L−1, organic matter degradation deteriorated. Degasification enhanced the propionate and acetate degradation. These results suggest that degasification reduced D-H2 concentration and volatile fatty acids concentrations, prevented pH drop, and subsequent enhanced organic matter degradation

Anaerobic treatment of municipal wastewater at ambient temperature: Analysis of archaeal community structure and recovery of dissolved methane

Anaerobic treatment is an attractive option for the biological treatment of municipal wastewater. In this study, municipal wastewater was anaerobically treated with a bench-scale upflow anaerobic sludge blanket (UASB) reactor at temperatures from 6-31℃ for 18 months to investigate total chemical oxygen demand (COD) removal efficiency, archaeal community structure, and dissolved methane (D-CH4) recovery efficiency. The COD removal efficiency was more than 50% in summer and below 40% in winter with no evolution of biogas. Analysis of the archaeal community structures of the granular sludge from the UASB using 16S rRNA gene-cloning indicated that after microorganisms had adapted to low temperatures, the archaeal community had a lower diversity and the relative abundance of acetoclastic methanogens decreased together with an increase in hydrogenotrophic methanogens. D-CH4, which was detected in the UASB effluent throughout the operation, could be collected with a degassing membrane. The ratio of the collection to recovery rates was 60% in summer and 100% in winter. For anaerobic treatment of municipal wastewater at lower temperatures, hydrogenotrophic methanogens play an important role in COD removal and D-CH4 can be collected to reduce greenhouse gas emissions and avoid wastage of energy resources

Removal of residual dissolved methane gas in an upflow anaerobic sludge blanket reactor treating low-strength wastewater at low temperature with degassing membrane

In this study, we investigated the efficiency of dissolved methane (D-CH4) collection by degasification from the effluent of a bench-scale upflow anaerobic sludge blanket (UASB) reactor treating synthetic wastewater. A hollow-fiber degassing membrane module was used for degasification. This module was connected to the liquid outlet of the UASB reactor. After chemical oxygen demand (COD) removal efficiency of the UASB reactor became stable, D-CH4 discharged from the UASB reactor was collected. Under 35°C and a hydraulic retention time (HRT) of 10 h, average D-CH4 concentration could be reduced from 63 mg COD L–1 to 15 mg COD L–1; this, in turn, resulted in an increase in total methane (CH4) recovery efficiency from 89% to 97%. Furthermore, we investigated the effects of temperature and HRT of the UASB reactor on degasification efficiency. Average D-CH4 concentration was as high as 104 mg COD L–1 at 15°C because of the higher solubility of CH4 gas in liquid; the average D-CH4 concentration was reduced to 14 mg COD L–1 by degasification. Accordingly, total CH4 recovery efficiency increased from 71% to 97% at 15°C as a result of degasification. Moreover, degasification tended to cause an increase in particulate COD removal efficiency. The UASB reactor was operated at the same COD loading rate, but different wastewater feed rates and HRTs. Although average D-CH4 concentration in the UASB reactor was almost unchanged (ca. 70 mg COD L–1) regardless of the HRT value, the CH4 discharge rate from the UASB reactor increased because of an increase in the wastewater feed rate. Because the D-CH4 concentration could be reduced down to 12 ± 1 mg COD L–1 by degasification at an HRT of 6.7 h, the 3 CH4 recovery rate was 1.5 times higher under degasification than under normal operation