Tadahiro Mori

Interactions of nutrients, moisture and pH on microbial corrosion of concrete sewer pipes

Abstract The heaviest corrosion occurred in the area around the sewage level of the concrete sewer pipe. The corrosion rate of this area was 4.3–4.7 mm/yr. The corrosion rates decreased according to the distance from the sewage level. The deterioration at the crown of the sewer pipe was lowest, 1.4 mm/yr. It is concluded that water and nutrients provided by sewage are important factors for microbial corrosion. Two corroded products were mainly produced, depending on pH levels. Gypsum was formed at pH levels less than 3 on the surface of the concrete sewer pipe and mortar specimens. On the other hand, ettringite was produced when pH levels were higher than 3 inside the specimens.

Stable abnormal foam in activated sludge process produced by rhodococcus sp. with strong hydrophobic property

Abstract The foam produced by Rhodococcus sp. in the aeration tanks of the activated sludge treatment plants was more stable than that formed by N. amarae. The stability was determined from the half time of foam decomposition. The stability depended upon the hydrophobicity characterized by the carbon numbers of mycolic acids. The Hydrophobic strengh of Rhodococcus sp. was higher than that of N. amarae. This was determined by using an index of log p = Po/ Pw, P and P are the partition coefficient of mycolic acid in solvent and water, respectively.

Some ecological observation on the decomposition of periphytic algae and aquatic plants

Abstract Stigeoclonium tenue, Chlamydomonas sp. and Chlorella sp., which are dominant periphytic algae in a shallow river (Tama-gawa, running through the Metropolitan area of Tokyo) were subjected to dark- and aerobic-decomposition tests using Selenastrum capricornutum as control. The decomposition of aquatic plants, Potamogeton crispus and Potamogeton pusillus which become dominant in the river mid- and downstream during summer was also studied. Successions of protozoa and smaller metazoa were noted from the decomposition tests. Regardless of the species of algae and aquatic plants studied the decomposition rate could be simulated as the 1st-order reaction if the refractory fraction, f of each organism was used as the datum of assessment. The value of f was roughly from 0.2 to 0.4, also irrespective of the organisms examined. The rate constant, k thus assessed extended from 0.08 to 0.2 day −1 at 20°C. Phosphorus and nitrogenous compounds regenerated into liquid (decomposer) amounted at 50th day of decomposition test to a level of 50 to 75% of that retained initially with the cells. Thus far, the seriousness of secondary pollution due to decomposition of periphytic algae and aquatic plants was pointed out. Lastly, the significance of removing nutrients from effluent of the wastewater treatment was demonstrated.

Biochemical studies on composting of municipal sewage sludge mixed with rice hull

Abstract A mixture of undigested sewage sludge cake with rice hull was composted and the changes in various biological and biochemical properties of the mixture were investigated in the process of composting. The salient features obtained were as follows: 1) The contents of T-C, T-N, and various carbon and nitrogen compounds did not show any significant variation during composting, although a slight decrease in the contents of acid hydrolyzable nitrogen compounds was detected at the initial stage of the composting (active composting). 2) Cellulase activity was low during active composting and increased after 23 days of the composting (curing). 3) Protease activity was low at the initial stage when the generation of NH, was active. 4) Tbe activities of the enzymes were higher when the temperature of the incubation was 60°C than when it was 30°C. 5) Predominant microflora consisted of aerobic bacteria throughout the composting period and no significant increase in the number of actinomycetes was observed wh...

Composting of municipal sewage sludge mixed with rice hulls

Abstract A mixture of undigested sludge cake with ground rice hulls as a bulking material was composted, and the changes in various properties of the mixture during active composting and curing were studied using a newly devised experimental apparatus for composting. The essential results obtained were as follows. 1. The temperature of the mixture was rapidly raised to 60°C by active composting and this level was maintained for more than 10 hr. 2. The concentration of gaseous NH3 and CO2 in the off-gases increased soon after initiation of the active composting and decreased to a low constant level on the 14th day, when the active composting was judged to be finished. 3. The BOD3 sharply decreased until the end of the active composting and maintained a low constant level thereafter. 4. The ignition loss gradually decreased during curing. These changes were found to be useful as indices for checking the process of composting.

Aspects of Microbial Ecology in New Technologies of Biological Wastewater Treatment

本総説は微生物生態学の概念を用いて,最近急速に進歩した生物学的排水処理技術を解析し体系化した。排水処理に要求されていることは(1)反応速度を速め装置をコンパクト化する。(2)処理効率を高め水質を向上する。(3)難分解性物質や有害物質を制御する。(4)極限条件下での処理方法の開発などである。このうち,(1)と(2)は微生物の生理・生態を活用し従来の生物処理技術を発展させることによって,かなりの程度まで対応できるようになった。すなわち,微生物生態学的にいえば,(1)場の管理による生物機能の発現または制御(2)微生物の高密度化および(3)微生物間の相互作用を導入したことによって優れた生物処理技術が生まれた,または生れつつあるといえよう。本総説は,水処理技術を上述の3つのグループに分け解析し体系化した。