The Nogawa river, which is a tributary of the Tama river in Tokyo, runs through a residential district. Stormwater runoff of petroleum hydrocarbons, such as linear aliphatic hydrocarbons and polycyclic aromatic hydrocarbons, was estimated from the viewpoint of atmosphere-land hydrosphere, roughly and based on mass-balance.
It seemed that the hydrocarbons in the river water at normal water levels were originated from 70-97% of gray water and those at high water levels were from 92-99% of runoff water. In petroleum hydrocarbons which influented to the river basin by storm water, 100% of linear aliphatic hydrocarbons with carbon numbers from 11 to 21 and 64% of those with carbon numbers from 21 to 30 were seemed to be originated from automobiles emissions.
On the contrary, 75% of polycyclic aromatic hydrocarbons were seemed to be originated from atmosphere, such as fossil fuels under incomplete combustion.
At high water level, the runoff loads of petroleum hydrocarbons in the Nogawa river was estimated to be 7.5-8.2% of all runoff in the land of the basin.

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Purpose of this study is to clarify the effects of sunlight, bottom sediment and biofilm support media on the capacity of natural purification in small channels fed with gray water. Model channels (depth=0.03m, width=0.08m, length=24m) made of PVC were used for the study. Hydraulic retention time (HRT) in the channels were 3. 2-13h. Specific conclusion of the study are as follows :
1) Removal of suspended solids (SS) in the channels was obvious. Percent removal of SS was more than 50% at HRT 3h. Percent removal of dissolved organic carbon (DOC), however, was less than 25% at HRT 3h.
2) Percent removal of dissolved nitrogen (D-N) and dissolved phosphorous (D-P) in open channels with sunlight tended to show larger value than that without sunlight. Removal of D-N and D-P was probably derived from the nutrient uptake by attached algae and prohibition of nutrients release from bottom sediment in aerobic condition made by photosynthesis of attached algae.
3) Accumulation of bottom sediment caused deterioration of water quality in channels in high temperature season, arising nutrient release from bottom sediment under depleted DO condition.
4 ) Support media settled on channel bed were not effective for purification of gray water. The media seemed to make low DO sites in channels and cause nutrients release from bottom sediment.

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The effects of temperature (5-35°C) and the volumetric BOD loading (0.9-5.5kg·m^-3·d^-1) on the structure of microbial film growing on the solid surface of packing materials and on the characteristics of the effluent were experimentally investigated in the aerobic submerged biofilter. It was clarified that the effluent quality is governed by the population of bacteria, while the growth of protozoa determines the microbial concentration in the biofilter. Au increase in the microbial concentration at a low temperature avoids the deterioration of effluent quality of the biofilter. The apparent retention time in the microbial film is in the order of organic matters > bacteria > protozoa, and the increased temperature shortens each retention time. Bacteria, protozoa and the extra-celler polymer take major part of the suspended solids in the effluent at low temperature, while the organic matters other than those at the high temperature.

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Recently, problems involving the pollution of water sources with pesticides used at golf courses have surfaced. We will report on the removal of some representative pesticides which are often detected and widely used at golf courses using the absorption qualities of mung bean roots. We were able to efficiently remove these pesticides in a short time, even a very low concentration. For standards of wastewater from golf courses, we obtained a high removal efficiency of 87 to 100% by a short time treatment (16 hours) with the insecticides fenitrothion, chloropyrifos, fungicides isoprothiolane, and chlorothalonil. The absorption efficiency for insecticide diazinon and fungicide captan was slow, however, 94% and 59% was removed, respectively, in a 2 day period. We assumed that the absorbed pesticides accumulated in high concentrations inside the body of the mung beans not influenced to their growth except chlorothalonil and simazine. This is shown by the result of the absorption of nutrients and the dry weight.

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The purpose of this study is to improve the removal efficiency of phenol and ammonium nitrogen simultaneously and to improve stability of effluent quality by the addition of support media with and without adsorption capacity into the aeration tank of activated sludge system and by the fixed-bed system. Granular activated carbon (GAC) and granulated slug (GS) with particle size from 0.2 to 0.4mm were added into the aeration tank of activated sludge system. The support medium used in the fixed-bed reactor was ceramics with a size of 30mm. An activated sludge system with no support medium was operated as a control system. The fixed-bed system could remove phenol and NH₄-N simultaneously since the activity of nitrification in the biofilm was high. Also, effluent phenol concentration during shock loading was kept low. In the activated sludge system added with GAC, effluent phenol concentration during shock loading was significantly smaller than those in the system added with GS and the control. The addition of GAC into the aeration tank enhanced phenol degradation activity. Adsorption of phenol on GAC might have contributed to the stable phenol removal during shock loading.

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