Water Pollution Continuous Monitoring Technology in Japan
Overview of Water Pollution Monitoring Conducted by Local Governments in Japan
Based on the law, Osaka Prefectural Government prepares its Measurement Plan for Public Water Areas and Underground Water Quality every year, and monitors water pollution under this plan.
Environmental Quality Standards serve as an effective guideline for determining items to be monitored, including evaluation criteria for measured values. Monitoring items and evaluation criteria (Environmental Quality Standards), are specified by the national government. The Basic Environment Law enacted in 1992, states the national government shall set standards concerning air pollution, water pollution, soil pollution and noise, so as to protect human health and preserve the living environment. Osaka Prefectural Government determines items to be monitored and monitoring frequency in the measurement plan for rivers and coastal areas, so measured values can be evaluated according to standard specified by the national government. To reinforce water pollution monitoring, the measurement plan is designed to include items whose criteria are specified in national effluent standards for water discharged from factories and establishments. In addition, the measurement plan includes items necessary to take measures for eutrophication issue.
(2) Measurement plan
Osaka Prefectural Government monitors water pollution based on the Measurement Plan it prepares each year. The Measurement Plan is determined by proposals under the Environmental Council of Osaka Prefectural Government, includes the following:
-Purpose
-Monitoring points and organization in charge of monitoring
-Monitoring period
-Items to be monitored
-Monitoring frequency
-Sampling method
-Measurement method
-Reporting measurement results
In Osaka Prefectural Government, 138 points for rivers and 22 points for coastal areas are monitored. Among these points, 87 river points and 15 coastal area points are designated as points to be applied to Environmental Quality Standards. Water quality at these points is monitored on a monthly basis so as to be judged to comply with Environmental Quality Standards. The remaining 51 river points and 7 coastal area points are designated as quasi-points, where water quality is monitored every 3 months (every month for some items.) Information obtained at these quasi-points is not directly judged for compliance with Environmental Quality Standards related to preserve the living environment. It is used instead as reference data for evaluation and compliance of items related to human health. Osaka Prefectural Government divides 73 river areas into 5 categories (A to E) and 8 coastal water areas into 3 categories (A to C), according to water use.
(Although national standards divide river areas into 6 categories from AA to E, there is no river in Osaka Prefecture Government which is classified as AA. National standards also include classification criteria for artificial and natural lakes of a volume of more than 10 million cubic meters, but Osaka Prefecture has no such lake.)
As to continuous monitoring of public water areas, items related to living environment are monitored according to standard designated for each category of water area, whereas items related to human health are monitored according to standard that apply for every pubic water area, including water area not included in the above-mentioned.
The governor of each prefecture is obligated to monitor water pollution. However, national government also gives the governor of each prefecture the privilege to entrust water pollution monitoring with the mayors of cities with more than 200,000 people, as well as the authority to use the results of water pollution monitoring by organizations managing a river. The measurement plan of Osaka Prefectural Government is designed so that the role of water pollution monitoring is shared by the Ministry of Construction, which is responsible for management of big rivers; and cities with more than 200,000 people (e.g. Osaka Prefecture has 10 cities); as well as by Osaka Prefectural Government.
Items to be monitored include 23 related to human health and 10 related to the living environment, for which Environmental Quality Standards apply; special items (for which effluent standards apply, or those necessary for water pollution control); specially designated items (trihalomithane production capacity for water purification plants); and other items (water temperature, color and odor). River flow rates and sediment conditions in coastal water areas are also monitored to measure water pollution.
River water samples are collected 4 times a day, as every 6 hours, because pollution levels are significantly fluctuated by human activity. Flow rate is measured when samples are collected. In coastal water areas, samples are collected once a day from both surface and bottom layers.
Collected samples are analyzed in various ways. For items of Environmental Quality Standards, analysis methods designated by the national government are used; for other items, analysis methods generally used by the national government or other official organization are used. When determining analysis method, the popularity of an analyzer is taken into account, as well as precision, sensibility and cost and process time of analysis. Some of items require more than one method of analysis.
(3) The selection of monitoring points
Monitoring points should be selected so as to meet the following requirements:
[1] Points not affected by a particular source of pollution
[2] Points at which samples representing the water quality of the area are obtained
[3] Points at which there is no difference in the quality of water among at the center of a river and its banks
In requirement [1] above, it should be noted that the purpose of monitoring described in this section is not to monitor waste water discharged from a particular factory or establishment, but to evaluate water quality according to water use at these points.
In requirement [2] above, problems may occur if water quality measured at the least polluted points complies with standards but becomes worse at its downstream. To ensure water quality, points representing water quality in an area should be where water quality is worst, or immediately upstream of water use.
In requirement [3] above, careful consideration is necessary for points downstream of one river joined another. Depending on river profile and flow rate, there may be cases where water quality near one bank is completely different from that near the other bank, and this difference lasts more than 10 kilometers; but that is rare in Japan. In such a river it is necessary to measure water quality at separate points along each bank, or to measure water quality in a river before it joins another. In Osaka Prefecture, water quality is measured in small-sized rivers by collecting samples from the center flow, whereas water quality is measured in medium-sized rivers by mixing sample water collected in the middle of the river and along its banks. In extremely wide-sized rivers (more than 300 meters wide), samples collected at the center flow and along each bank are separately measured.
(4) Selection of items to be monitored
All items designated by Environmental Quality Standards are monitored and subject to evaluation for compliance with the standards. As to points for which no Environmental Quality Standards apply (for example, the number of coliform groups in water areas of category E), all items are not always monitored.
Fluorine and zinc designated by effluent standard are measured at all monitoring points as "specific items". So are nitrogen (nitrate, nitrite, organic-nitrogen) and phosphorus (phosphoric acid), which play a critical role in eutrophication.
The number of plankton is also measured at all monitoring points for coastal water.
In water areas used as a source for tap water, the production capability of trihalomethane, which is pointed out to be carcinogenic, and "items requiring monitoring" which are in consideration to application for Environmental Quality Standards are also measured. The measurement plan by Osaka Prefectural Government does not include "items requiring monitoring".
Sediment quality is also measured in coastal water. Accumulated mercury and PCB in sediments are considered capable of dissolving in seawater. To prevent the pollution of seawater by these substances, removal standard value is designated because elution-substances from sediments may pollute seawater. Samples of sediment in coastal water areas are collected every 6 months, and their compliance with standards is evaluated. Other items for sediments are also measured, because sediments are suppose to have something to do with low oxygen and eutrophication in seawater, directly affecting the living environment of marine creatures.
|
Human-health-related items A |
Human-health-related items B |
|
|
Rivers and Coastal water areas |
Total cyanide Lead Chromium Arsenic Total mercury |
Alkyl mercury, Polychlorobiphenyl(PCB), Dichloromethane, Tetrachloromethane, 1,2-dichloromethane, 1,1-dichloroethylene, 1,1,1-trichloroethane, 1,1,2-trichloroethane, Trichloroethylene, Tetrachloroethylene, 1,3-dichloropropene, Thiram, Simazine, Thiobencarb Benzene, Selenium (Altyl mercury is measured only when total mercury is detected.) |
|
Rivers |
pH, Dissolved Oxygen(DO), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD: acid method), Suspended Solid (SS), Number of Coliform groups, Total Nitrogen, Total Phosphorus |
|
Coastal water areas |
pH, Dissolved Oxygen (DO), Chemical Oxygen Demand (COD: acid method, alkali method, filtration acid method), Number of Coliform Groups, N-hexane Extract (oil content), Total Nitrogen, Total Phosphorus |
|
Rivers |
N-hexane extract (oil content), Phenol, Copper, Zinc, Dissolved Iron, Dissolved Manganese, Total Chrome, Fluorine, |
|
Coastal water areas |
Phenol, Copper, Zinc, Dissolved Iron, Dissolved Manganese, Total Chrome, Fluorine, Anionic Surface Active Agent, Number of Plankton, Chlorophyll a, Nitrite Nitrogen, Nitrate Nitrogen, Ammonia Nitrogen, Phosphorus Phosphate, Suspended Solid (SS), Ignition Loss of Suspended Solid, Turbidity, EPN |
|
Rivers |
Trihalomethane Production Capacity |
|
Rivers |
Ambient temperature, Water temperature, Color, Odor, |
|
Coastal water areas |
Ambient temperature, Water temperature, Color, Odor, Transparency, Salt Content, etc. |
|
Coastal water areas |
Cadmium , Total Cyanide, Lead, Arsenic, Total Mercury, |
|
Coastal water areas |
pH, Chemical Oxygen Demand, Water Content, Sulfide, Oxidation / Reduction Potential, Ignition Loss, Total Chromium, N-hexane Extract (oil content) |
|
Coastal water areas |
Water depth, Characteristics, Color, Odor, |
|
Group |
Items related to living environment Other items |
Items related to human health |
Special items | |
|
Items related to human health A |
Items related to human health B | |||
|
I-A |
At least 12 times / year |
At least 6 times / year |
At least 4 times / year |
At least once / year |
|
I-B |
At least 4 times / year |
At least 2 times / year | ||
|
I-C |
At least 4 times / year |
At least 2 times / year |
||
|
Group |
Items related to living environment Other items |
Items related to human health |
Special items | |
|
Items related to human health A |
Items related to human health B | |||
|
II-A |
At least 12 times / year |
At least 4 times / year (PCB: at least once / year) |
At least once / year | |
|
II-B |
At least 4 times / year |
|||
Other items |
|
Measurement frequency |
Month |
Once / year |
August |
Twice / year |
August. and February in the following year |
4 times / year |
May, August, November, and February in the following year |
6 times / year |
May, July, August, November, and January and February in the following year |
(5) Measures taken upon detection of abnormal water quality
Should concentration value over standards be detected for any substance, the following measures must be taken.
(a) Items related to human health
If any measured value does not conform to standards for items related to human health, the cause should be identified and proper measures should be taken to the party with water rights.
For water use, information about abnormal water quality is given to water supply authorities, farms and fisheries and industrial water users. Such information is particularly important for water supply authorities. Since any water supply authority is also continuously monitoring water quality itself, pertinent information is exchanged when abnormal water quality is detected.
To identify a source of pollution, potential upstream sources are investigated. Cooperation may be necessary with the organization managing a river. It may also be necessary to provide notice and information to municipalities situated to upstream in addition to the following investigation.
-Measurement of water pollution at points upstream (including points upstream from where rivers join)
-Investigation of waste water discharged from factories or establishments using a targeted pollutant. (Water and sediments at points close to a discharge port and liquid inside an oil-water separation tank may also be analyzed to trace the discharge of a pollutant.)
-Collection and confirmation of information regarding illegal disposal or accidental discharge
As for metal compounds, they are sometimes discharged naturally from the ruins of mines, or when metal compounds with a heavy accumulation in sediments are dissolved in river water because of construction for river improvements. Water pollution caused by such metallic substances is usually temporary, and the concentration is very subtle. However, if standards are exceeded for a long time, proper measures may be necessary, including replacement of sediments. (Osaka Prefecture has never had such serious pollution.)
Several times a year, some items related to human health have been detected in rivers in Osaka Prefecture. Half of those substances are discharged from factories or establishments; the other half are due to natural discharge and discharge from sediment. However, in the 3 years from 1995 to 1997, exceeding standard values for one item was only experienced at one monitoring point. Since items other than total cyanide and mercury are evaluated according to their mean value for a given year, Environmental Quality Standards are complied if their annual mean value is less than the standard despite of some excess of the standard or some detection. In Osaka Prefecture, items related to human health have not be detected for coastal water during the past several years.
(b) Items related to the living environment
Certain rivers chronically exceed standards for BOD, which Environmental Quality Standards designate as related to the living environment. This is due mainly to the following factors:
If the water pollution results from any illegal activity by a factory or establishment, proper supervisions are taken against them. In case of chronic excesses of standard, however, it is difficult to take immediate countermeasures against the source of pollution. A long-term measures, such as promoting sewage treatment and proper water quantity control, will be necessary.
Osaka Prefecture is notorious for having many rivers that are contaminated with high concentrations of BOD. Many of these rivers suffer pollution due to more than one of the factors mentioned above. Although the level of pollution has gradually been reduced since 1970, it remains quite high when compared to the average level all across Japan. Only 30 out of 73 rivers comply to applicable standards(i.e. less than 50% as rate of compliance). In coastal water areas, only coastal bay areas, for which the standard is less strict, satisfy the applicable criteria. No central bay area or fishery area comply to the applicable standards.
