1 Professor, Faculty of Environmental and Information Studies, Musashi Institute of Technology2 Visiting researcher, Faculty of Environmental and Information Studies, Musashi Institute of Technology

Implications of an Assessment of Bacteriological Water Qualityin the Tama River Basin

Hiromi Kobori1, Young-Sik Ham2

研究論文 1-5

1. IntroductionThe Tama River is the longest river in Tokyo Metropolitan area and has historically played an

important role in the recreational, spiritual, and aesthetic use of water resources and riparianspace. Today, the Tama River is a typical urban river flowing through densely populated areas ofTokyo. Although the water quality of Tama River basin was greatly damaged by the influx of do-mestic and industrial wastewater during a period of high economic growth about 40 years ago, thewater quality measured by BOD in Tama River has gradually improved with the increase in theproportion of sewer penetration in the Tokyo Metropolitan area from an average 21% in 1965 to98% in 2004 [1]. However, according to Hiraishi et al. (1984) and Japanese Ministry of Construc-tion (1998) (Present name : Ministry of Land, Infrastructure and Transport, Government of Ja-pan), the bacteriological water quality of Tama River was unsatisfactory during 1978−1996, duringwhich time it exceeded the maximum acceptable concentration of total coliform (TC) bacteria(5000 cfu/100 mL) that had been set as the environmental quality standard for rivers by the Japa-nese government’s Ministry of the Environment [2, 3]. In a case study, it was reported that mostof TC bacteria concentrations in 10 rivers in Mie Prefecture, located in a part of the Kinki regionon the island of Honshu, Japan, were observed at levels above the maximum acceptable level ofTC bacteria during 1983−1994 [4]. Furthermore, it was reported that during 2003−2006, 20−24%of rivers classified as ‘Class A’ in Japan exceeded the maximum acceptable concentration of fecalcoliform (FC) bacteria (1000 cfu/100 mL) by a bathing water quality criterion established by Min-istry of the Environment, Government of Japan [5−7]. These FC bacteria generally originate fromthe fecal materials of warm-blooded animals (e.g., humans, pets, livestock, and wildlife).

This study discusses the implications of the bacteriological water quality of Tama River basinin relation to total and fecal coliform bacteria.

2. Materials and methods

2.1. Description of study areaPortions of the Tama River basin in the Tokyo Metropolitan area and Kawasaki City were se-

lected for this study (Figure 1). The Tama River is approximately 138 km long and flows south-east into Tokyo Bay from its source on Mt. Kasatori (elevation : 1953 m) in Yamanashi and Sai-

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Figure 1. Research points in the Tama River basin in Tokyo and Kawasaki City. Open circle St. 1and St. 2 : upstream stations on the Tama River, St. 3 and St. 9 : midstream stations, St. 4, St. 5and St. 6 : tributary stations, St. 10 and St. 11 : downstream stations, St. 7 : raw water station, andSt. 8 : TSE station.

tama Prefectures. The western part of Tokyo Metropolitan area is composed of 24% combinedsewer systems and 76% separated sewer systems [8]. In contrast, the eastern part of Tokyo Metro-politan area employs 82% combined sewer systems and 18% separated sewer systems [9]. In addi-tion, the study area of Kawasaki City adjacent to the downstream Tama River shows nearly 100%separated sewer systems [10]. The sampling stations were selected in upstream Tama River (St. 1and St. 2, residential areas of relatively low density), midstream (St. 3 and St. 9, residential areasof relatively high density), tributary stream (St. 4, St. 5 and St. 6, residential areas of relativelyhigh density), raw water influent (St. 7), treated sewage effluent (St. 8), and downstream (St. 10and St. 11, residential areas of relatively very high density) (Figure 1).

The annual average air temperatures in Tokyo were 16.1 ± 0.7°C (average ± SD) ranging from5.9°C (monthly minimum) in January to 27.1°C (monthly maximum) in August during 1976−2005. Average precipitation during this same period was 1484 ± 262 mm, ranging from 38 mm(monthly minimum) in December to 203 mm (monthly maximum) in September [11].

2.2. Sampling and bacteria counting methodsOnce a month during June 2003−January 2005, water samples were collected almost simulta-

neously in the 3 upstream, 3 tributary, and 3 downstream stations of the Tama River and at 1 sta-tion each of raw water influent and treated sewage effluent of a sewage treatment plant, usingsterilized 100 mL glass bottles. All the water samples were immediately deposited into a hand-held icebox to keep the temperature below 4°C. These samples were immediately used for labora-tory experiments in a field work facility at the Faculty of Environmental and Information Studies,

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Figure 2. The percent ratio of the number of samples exceeding the maximum acceptableconcentration of TC bacteria (5000 cfu/100 mL) set by the environmental quality standardfor rivers established by the Ministry of the Environment, Government of Japan.

Musashi Institute of Technology.The standard plate count (SPC) bacteria were determined by spreading 0.1 mL of the river

water sample onto a standard method agar (Eiken Chemical Co., Ltd., Japan) plate [12−14] andincubating the plate for 5 days at 20°C. The colonies appearing on the plates were counted asSPC bacteria. Total coliform (TC) bacteria were determined by spreading the sample on a desoxy-cholate agar plate (Eiken Chemical Co., Ltd., Japan) and incubating the plate for 18 hr at 36 ± 1°C [12−14]. The same procedure of the TC count was used to count fecal coliform (FC) bacteriaexcept that the plates were incubated at 44.5 ± 0.2°C for 18 hr [12]. The red-colored colonies ap-peared on the plates were counted as TC and FC bacteria.

3. Results and discussion

3.1. Bacteriological water quality in the Tama River basinDuring the study period, the downstream and tributary stations of Tama River basin showed

considerably higher rates of concentrations in excess of the maximum acceptable concentration ofTC bacteria (5000 cfu/100 mL) set by the environmental quality standard for rivers and FC bacte-ria (1000 cfu/100 mL) by a bathing water quality criterion established by the Ministry of the En-vironment, Government of Japan, compared with those of the upstream and midstream stations(Figure 2 and 3). The Water Quality Bureau of Japanese Environment Agency (Ministry of theEnvironment, Government of Japan) has reported that Salmonella was detected at 100% rate in

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Figure 3. The percent ratio of the number of sample exceeding the maximum acceptableconcentration of FC bacteria (1000 cfu/100 mL) by a bathing water quality criterion estab-lished by Ministry of the Environment, Government of Japan.

the range of FC bacteria concentration�1000 cfu/100 mL [15]. The rates at which excessive con-centrations were found ranged from 21% to 100% in TC bacteria concentrations and from 0% to68% in FC bacteria concentrations. In the raw water influent samples, almost 100% of the TC andFC bacteria concentrations were over the maximum acceptable concentration of TC and FC bacte-ria (Figure 2 and 3). On the other hand, the treated sewage effluent samples indicated relativelylow excess rates (<50%) for the maximum acceptable concentration of TC and FC bacteria, re-spectively.

The downstream and tributary Tama River basin areas showing the higher excess rate for themaximum acceptable concentration of TC bacteria (in accordance with environmental quality stan-dards for rivers) and FC bacteria (in accordance with a bathing water quality criterion) are com-posed of residential areas of relatively high population density. These results support the hypothe-sis that the Tama River is contaminated with bacteria originating from anthropogenic sources.

3.2. Relationship of fecal and total bacteriaThe TC and FC bacteria concentrations showed a significant positive correlation in the Tama

River basin (Figure 4). The linear regression equation using log of FC bacteria concentration asoutcome variable (y) and log of TC bacteria concentration as predictor variable (x) was y = 0.762x − 0.387 (p < 0.001). About half of samples tested for FC bacteria concentrations exceeded themaximum acceptable concentration of FC bacteria (1000 cfu/100 mL) according to a bathingwater quality criterion (Figure 4). Similarly, FC bacteria concentrations in more than 50% of 20

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Figure 4. The correlation and linear regression equation of totaland fecal coliform bacteria concentrations in the Tama River ba-sin. Dashed vertical line : the maximum acceptable concentrationof TC bacteria (5000 cfu/100 mL) set by the environmental qual-ity standard for rivers, dotted horizontal line : the maximum ac-ceptable concentration of FC bacteria (1000 cfu/100 mL) by abathing water quality criterion. ***Correlation is significant atthe 0.001 level (Spearman’s correlation coefficient test, 2−sided).

research points in the Naka River basin in Tochigi Prefecture located in a part of the Kanto regionon the island of Honshu, Japan were over the maximum acceptable concentration of FC bacteria[16]. The United States Environmental Protection Agency (1997) has been recommending a crite-rion of 400 cfu/100 mL for FC bacteria during May−October [17], which is stricter than the stan-dard used in Japan. In the state of Georgia in the southeastern U.S., 30-day geometric mean stan-dards for FC bacteria are 200 cfu/100 mL during May−October and 1000 cfu/100 mL during No-vember−April, and a maximum acceptable level for single sample of 4000 cfu/100 mL during No-vember−April has been used [18]. In Georgia’s water quality control regulations, May−October isregarded as the period when recreational activities involving direct contact with water (swimming,boating) are expected to occur. If the stricter of Georgia’s fecal coliform standards were applied toJapanese rivers, it would be extremely difficult to meet the standard. However, water contact rec-reation activities are not expected to occur in urban rivers in Japan, so the stricter standard maynot be necessary.

A large portion of TC bacteria concentrations were in excess of the maximum acceptable levelof TC bacteria (5000 cfu/100 mL) set by the environmental quality standard for rivers establishedby the Ministry of the Environment, Government of Japan (Figure 4). Some people have been ar-guing against the maximum acceptable level of TC bacteria, saying that 5000 cfu/100 mL is toohigh for the maximum acceptable level of TC bacteria in the environmental quality standard forrivers. In a case study, most of TC bacteria concentrations in 10 rivers in Mie Prefecture locatedin a part of the Kinki region on the island of Honshu, Japan were observed over the maximum ac-ceptable level of TC bacteria during 1983−1994 [4]. The Ministry of Land, Infrastructure andTransport, Government of Japan (2005) has suggested using FC bacteria concentration instead ofTC bacteria as the indicator of bacteriological water quality in public health in rivers [19]. Even

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4. ConclusionsThe Tama River basin showed high rates of exceeding maximum acceptable concentrations of

TC bacteria, set by the environmental quality standard for rivers, and FC bacteria, set by a bathingwater quality criterion. The Tama River basin was highly contaminated by bacteria originatingfrom anthropogenic sources. Consequently, there is still a risk potential for pathogenic bacteria inthe Tama River basin.

The maximum acceptable concentration of TC bacteria set by the environmental quality stan-dard for rivers and FC bacteria by a bathing water quality criterion should be established onharmful levels of pathogens in human and other animals.

AcknowledgementsThis study was supported in part by the Ministry of Education, Culture, Sports, Science and

Technology of Japan (Grant No. 16500561) and the Tokyu Foundation for Better Environment(Grant for Academic Research No. 257).

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