A linear regression model for pollution load potential is developed to estimate both runoff loads of pollutants and nutrients and wastewater loads derived from water-uses of human beings. The pollution load potential, defined as the annual total load per unit area of a river catchment, is expressed as a linear function of the annual total flow per unit area of the catchment. This model suggests that the greater the annual total flow is, the higher the pollution load potential becomes.
During a period of 1978 to 1991, using the data of various water quality indicators for eleven rivers inflowing to Lake Kasumigaura, the linear regression model was applied. Comparison between the model and the observed data yielded high regression coefficients. These results suggest that the wastewater loads should be cut as much as possible to decrease the potential of these rivers. Secular changes in the potentials can be evaluated by examining the slopes of regression lines between two sets of data group, before 1982 and after 1987. During a period of 1982-1987, the phosphorus and pollutants loads from domestic grey water decreased considerably because of the switching from detergents with phosphate to ones free from phosphate and the basin-widening of sewer systems.

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Organic carbon in suspended solid (SSOC) in urban surface water in Kawasaki was measured with the use of elemental analyzer. Through this method was in particular examined SSOC concentration on it and relationships between total organic carbon (TOC) and other items as well.
SSOC mean concentration in urban surface water was 8.4mg·l^-1, and mean content of SSOC in TOC (SSOC plus dissolved organic carbon) was 47.9%. Variation of biochemical oxygen demand (BOD) concentration at relatively polluted point was much dependant on SSOC concentration. Carbon, hydrogen and nitrogen in suspended solid were thought to compose organics, to which mean composition ratio of C: H : N was 1: 2: 0.15.
TOC, BOD and COD were highly correlated.

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Benthic denitrification activities were determined monthly at two locations with different types of riverbeds in Nogawa River, a typical urban stream, by the acetylene inhibition technique during one year from December 1987. The annual mean denitrification rate at the upstream site N-2, 1.6mgN m^-2h^-1, where the channel of the river was covered with concrete was higher than the rate at site N-3, 0.8 mgN m^-2h^-1, of which riverbed was composed of sands and gravels. The discrepancy of denitrification activity between the two points is probably due to the structural difference of microbial habitat, which originates mainly from surface conditions of the riverbeds. The average fraction of denitrified nitrogen to inorganic nitrogen load, on the other hand, was lower at the site N-2 as 0.3% than at the site N-3 as 2.3%, when each residence time of river water was taken into consideration. In case that the entire channel of Nogawa River was composed of sands and gravels, the ratio of the denitrified nitrogen within the river sediment to the total inorganic nitrogen flux at the site N-2 should be calculated at 2. 5%. On the contrary, if the whole river bed was covered with concrete, the ratio should drop to 1.3%. Thus, anthropogenic alteration of the riverbed affects in some extent the nitrogen removal by benthic denitrification in Nogawa River.

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Cu ions in waste water can be removed by ferrite treatment, but the reduction of Cu²⁺ by Fe²⁺ and the mechanism of Cu⁺-ferritization are not made clear.
In this paper, the authors studied the behavior of Cu²⁺ and Fe³⁺ in the ferrite treatment with chemical analysis and X-ray diffraction and the dissolution of Cu from products obtained by the ferrite treatment. Cu²⁺ was almost reduced to Cu⁺ before aeration and Cu⁺ existed as Cu₂O. But Cu₂O in the suspension was oxidized to CuO after the oxidation of Fe²⁺, and CuO is easy to dissolve in acidic condition.

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Seasonal change of nitrate concentration in the artesian wells ware investigated. The wells are around the paddy field in Tsukuba, Ibaraki prefecture. Nitrate is observed in the wells those dissolved oxygen concentration in relatively high. Ammonium is observed in the anaerobic wells. The average concentration of nitrate in every wells are under 10mg·l^-1, however high concentration over 10mg·l^-1 are observed in certain wells in summer season.

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