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水環境の現状

Water Use and Environment in Japan – Current State of Water Environment

日本の水環境の現状

 戦後の高度成長期における産業活動の急速な拡大と人工の都市集中に伴い、環境水の深刻な水質汚濁が進行した。こうした事態に対し、昭和45年、公害対策基本法の改正および水質汚濁防止法が制定され水質汚濁に係わる環境基準や工場排水基準が定められてから水環境は総体的には改善傾向にある。

Current state of water environment in Japan

 Due to the rapid expansion of industrial activities and the concentration of man-made cities during the post-war period of high growth, serious pollution of environmental water has progressed. In response to this situation, the water environment has been improving as a whole since the Basic Pollution Control Law was revised and the Water Pollution Control Law was enacted in 1965 and the environmental standards relating to water pollution and factory drainage standards were established.

発生源

 日常生活や産業活動に伴う主な水質汚濁の発生源をに示す。日常生活に伴う排水も環境への大きな負担となっている。生活排水におけるBOD負荷量の割合を発生源別に見ると、台所4、し尿3、風呂2、洗濯1となっている。生活排水対策として下水道や合併浄化槽の整備などが進められている。このほかに、市街地、土地造成現場、農地などの非特定汚染源から降雨などにより流出する汚濁負荷や過去に沈殿、堆積した底質からの栄養塩類の溶出による汚濁が我が国の水質汚濁の要因となっている。

Generation source

 The main sources of water pollution associated with daily life and industrial activities are shown in the table below. Drainage from daily life is also a heavy burden on the environment. Looking at the percentage of BOD load in domestic wastewater by source, it is kitchen 4, human waste 3, bath 2, laundry 1. As a measure for domestic wastewater, the construction of sewers and combined septic tanks (Johkaso) is being promoted. In addition, the pollution load that flows out from non-specific pollution sources such as urban areas, land development sites, and agricultural land due to rainfall, etc., and the pollution caused by the elution of nutrients from sediments that have sedimented and accumulated in the past are factors that contribute to water pollution in Japan.

表 水質汚濁の発生源 Table Sources of water pollution
poll_source

公共水域

カドニウムなど、人の健康に関わり有害な物質である健康項目については大幅な改善がみられ、平成25(2013)年度の達成率は約99.2%である。一方、生活環境項目であるBODまたはCODについての環境基準の達成率[1]は全体で87.3%で、河川で92.0%、湖沼で55.1%、海域で77.3%であった。なお、達成率は、達成水域数の類型指定水域数に対する割合である。水質汚濁防止法制定以来、河川は着実に改善されているが、湖沼、内海、内湾などの水の出入りが少ない停滞性の水域(閉鎖性水域)の水質改善状況は横ばい、または緩やかな改善傾向である。
 閉鎖性水域は外部との水の交換が行われにくく汚濁物質が蓄積しやすいため水質の改善や維持が難しく、河川や海域に比べて基準の達成率が低い。また、クリストスポリジウムなどの新種の病原性微生物、環境ホルモンと呼ばれる内分泌攪乱作用の恐れのある化学物質、あるいは廃棄物処分場からの浸透水による水質汚染が問題化している。

Public waters

 Significant improvements have been seen in health items such as cadmium, which is a harmful substance related to human health, and the achievement rate in FY2013 was approximately 99.2%. On the other hand, the achievement rate of environmental standards [1] for BOD or COD, which is a living environment item, was 87.3% overall, 92.0% for rivers, 55.1% for lakes, and 77.3% for sea areas. The achievement rate is the ratio of the number of achieved water areas to the number of type-designated water areas. Since the enactment of the Water Pollution Control Law, rivers have been improving steadily, but the water quality improvement status of stagnant water areas (closed water areas), such as lakes, inland seas, and inner bays, is flat or is gradually improving.
 In closed water areas, it is difficult to exchange water with the outside and pollutants easily accumulate, so it is difficult to improve and maintain water quality, and the rate of achievement of standards is low compared to rivers and sea areas. In addition, new types of pathogenic microorganisms such as Christosporidium, environmental chemicals called endocrine disrupting chemicals, and water pollution from permeated water from waste disposal sites are becoming a problem.

地下水

 地下水は有機塩素化合物および硝酸性窒素による汚染が明らかになっている。地下水は一旦汚染されると、快復するまで長い年数を必要し効果的な対策も困難であるので、汚染に対して特に注意が必要である。地下水汚染では、硝酸塩、亜硝酸塩、消化器病原菌などがある。有害物質による汚染では、クロム(VI)化合物によるもものが最も多く、水銀、シアン、カドミウム、ヒ素、有機リン化合物、鉛について小数ながら報告されている。塩素系溶剤による地下水汚染は、我が国でも広範な汚染が確認されている。

Groundwater

 Groundwater is known to be contaminated with organochlorine compounds and nitrate nitrogen. Once the groundwater is polluted, it takes a long time to recover and it is difficult to take effective countermeasures. Groundwater pollution includes nitrates, nitrites, and gastrointestinal pathogens. Chromium (VI) compounds are the most common pollutants due to harmful substances, and mercury, cyanide, cadmium, arsenic, organophosphorus compounds, and lead have been reported in small numbers. Groundwater pollution by chlorine-based solvents has been confirmed to be widespread in Japan.


掲載日:2016年07月09日
Posted: July 9, 2016
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