This paper concerns the simultaneous nitrification and denitrification in a completely mixed bio-reactor with the partially and fully submerged rotating biological contactors. In the bio-reactor nitrification and denitrification mainly occur in the partially and fully submerged RBCs, respectively, and organic material contained in the influent can be used as the organic source of denitrification. An experimental investigation was made into the effect of the species of the organic material and influent C/N ratio on the simultaneous nitrification and denitrification.
In the first run where settled municipal wastewater was fed into the reactor, efficiency of nitrification and denitrification was about 80% and 60% with the hydraulic retention time of 6 hours in the summer, respectively. Similar efficiency was obtained with the hydraulic retention time of 13 to 17 hours in the winter. In the second run, diluted digester supernatant with acetate or ethylene-glycol was fed into the reactor. Influent NH₄-N concentration was about 120 mg·l^-1 and C/N ratio was set at a desired level by changing the influent concentration of acetate or ethylene-glycol. The hydraulic retention time and water temperature were kept at 25 hours and 25°C, respectively. The highest nitrogen removal efficiency was almost 90 % in the C/N ratio of around 3 and 2 for acetate and ethylene-glycol, respectively.

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Laboratory scale continuous-flow activated sludge reactors were operated using synthetic wastewater containing phenol as a toxic organics, m-aminobenzoic acid (m-ABA) as a refractory organics and inorganic nutrients to clarify the effects of powdered activated carbon (PAC) on removal of the toxic and refractory organics. The performance of the activated sludge system operated with the addition of PAC was compared with that of the system operated with the addition of bentonite (BEN), the system operated with the addition of raw material of PAC (NAC) having no ability to adsorb and the system of conventional activated sludge (AS).
Concentrations of DOC, phenol and m-ABA in the effluent of the reactor with PAC were much lower than those when other adsorbents were used. Especially, the m-ABA were not detected (< 0.2mg·l^-1) in the effluent from the reactor with PAC, while those for BEN, NAC and AS were 80, 75 and 80 mg·l^-1, respectively. Because contribution of adsorption of m-ABA on PAC to the removal of m-ABA was negligible, m-ABA was considered to be removed through biodegradation. Thus, biodegradation activity to phenol and m-ABA were much improved by the addition of PAC.
The microbial compositions in these systems were also determined by viable counts using nutrient broth medium, phenol-selective medium, and m-ABA-selective medium and by quinone profiles, respectively. As results, the microbial compositions in these systems were almost the same, irrespective of the difference in support media. Therefore, improvement of the biodegradation activity with the addition of PAC would be explained from the increase of individual bacterial activity due to the addition of PAC to activated sludge.

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Anaerobic degradation of particulate organics in fludized bed reactor was investigated by using a synthetic wastewater (2 g-COD·l^-1) containing 25% cellulose of the influent COD. The cellulose removal efficiency of the reactor was achieved up to 98% over COD loading 0.5-2 g·l^-1·d^-1. The cellulose content in biofilm increased from 2 to 16% of MLVSS with an increase in COD loading from 2 to 10 g·l^-1·d^-1. An excessive accumulation of cellulose caused to weaken the mechanical strength of biofilm. Accordingly, SRT (Solids Retention Time) decreased significantly from 80 days to 2.6 days.
The microbial activities of biofilm, with respect to cellulose-degradation, glucose-degradation, acetate-production and methane-production (from H₂ and from acetate) were determined at regular intervals during 140-days experimental duration by a serum vial test method. The activity test suggested that the shift in the microbial population constituents occurred during biofilm development. The propagations of acid-producing bacteria and acetate-utilizing methanogenic bacteria were by far more prominent than those of the other trophic groups. The cellulose degradation activity of biofilm rose gradually up to 0.2 g-Cellulose·g^-1VSS·d^-1.

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For aromatic compounds, mono- and di- carboxylic acids and monohydric alcohols, the adsorption equilibria from their aqueous solutions onto a granular activated carbon were determined. Then, the equilibrium data were expressed by Freundlich type and the equilibrium constants k and n were obtained. The products k·n and the values of n for those organic compounds were correlated with the molar refraction R_m and the molecular volume V_m, respectively.
Then, the relationship between the products and R_m was shown, as follows.
log k·n=21.6 R_m+0.953-0.215 N_f (N_f : number of hydrophilic functional group)
The products for isomers of butanol could be corrected by use of that for the linear molecule as the standard one and the ratio of those boiling points T_B/T_B,0, and the effect of adsorption temperature on the products was estimated by comparing with the value at standard temperature T₀, as follows.
k·n=(k·n)₀ (T_B/T_B,0)^4.2 and k·n=(k·n)₀ (T₀/T)
Also, the value of n was correlated with V_m and the effect of adsorption temperature on n was estimated, as follows.
log n=0.833 log V_m+3.72 and n=n₀ (V_m/V_m,0)^0.833 (T₀/T)
where n₀ and V_m,0 indicate n and V_m at standard temperature T₀, respectively.

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Simple methods for pH and COD measurements of waste and natural waters by use of commercially available pH indicator papers (Universal Test Papers, roll type, Advantec Toyo, Tokyo) and reagent packs for pH and COD measurements (PACK TEST WAK-pH, and WAK-COD, Kyoritsurikagaku, Tokyo) have been compared with the official methods, i.e., the glass electrode method for pH measurement and the potassium permanganate method for COD measurement.
pH of waste, river, ground, and rain waters were measured by the official method, the pH test paper, and Ion Selective PACK TEST. The pH values obtained with PACK TEST were in good agreement with those by the official method. On the other hand, the test paper showed a tendency to give the higher pH values for the acidic samples and the lower values for the alkaline samples than the official method.
The COD values of river waters were measured by PACK TEST and the official method. The values obtained by these methods were correlated with each other and the regression curve is as follows :
y=0.71x-1.17 (r=0.912, n=35)
were x represents the values measured by the official method and y the values measured by PACK TEST. The COD values of waste waters obtained by PACK TEST were also correlated with those by the official method, except the samples which contain much SS.
When PACK TEST COD was calibrated by using synthetic domestic waste waters instead of glucose standard solutions, it gave the more similar COD values to those obtained by the official method for river and domestic waste waters.

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