The purpose of the Total Maximum Daily Loading (TMDL) regulation is to reduce the total amount of loading into large, closed water bodies faced with serious pollution. The reduction must be uniform and effective for all the activities in the basin including the inland area. The basic policy for the regulation is as follows.

(specified basin) the entire drainage basin for the specified waters. The Prime Minister formulates the basic policy for TMDLs to avoid inequality among prefectures,

(total loading) the total amount of loading to be reduced, includes not only those from industries under control by the Water Pollution Control Law, but also those without regulations such as domestic wastewater,

(target of TMDL) should be specified for each source,

(implementation) all the industries in the specified basin are required to comply with the target of the TMDL. Also, regulation of the TMDL requires construction and improvement of sewage systems, on-site treatment plants, small-scale industrial wastewater treatment processes, and environmental education,

(loading to be regulated) total daily loading by the specified effluents originating mainly from production processes. No regulation for indirect cooling water and rainwater,

(monitoring) each industry must monitor and file daily loading reports based on the specified procedure to estimate total daily loading.

The governmental ordinance defines specified water, basin (drainage basin for the water), and parameters (parameters to be regulated) for the regulation of TMDLs. Specified waters are large polluted enclosed water bodies with a drainage basin having concentrated human activities and a high potential of pollution loading. Specified basins are the drainage basins of the specified water.

• specified water: Tokyo Bay, Ise Bay, SetoInland Sea
• specified parameter: COD, nitrogen, phosphorus
• specified basin: all the drainage basins of the specified waters in 20 prefectures

The Prime Minister is responsible for the basic policy TMDL policy. The policy for the lst TMDL in 1979 was based on the following information:

• present loading of COD
• target and year of TMDL within the possible limit, taking into consideration increases in loading associated with the developments of industrial activities and population growth, developments of wastewater treatment technology, and percent service of sewerage systems in the basin,
• target of TMDLs for each activity and prefecture.

The regulation of TMDLs requires defining the target of the maximum daily loading for COD into the specified water from each activity in each prefecture in the target year.

Since 1979 a series of plans under five-year plans has been put into effect. The first four pollutant control plans set targets for COD, followed by inclusion of targets for nitrogen and phosphorus in the fifth pollutant control plan. The targets for 2009 were enforced in November 2006 under the sixth pollutant control plan.

The plan for the lst TMDL was issued in 1980. The governor of each prefecture is responsible for making the TMDL plan based on the basic policy for TMDLs as follows:

• target of TMDLs for each activity
• measures to implement the target

Major management plans to attain the target of TMDL are as follows:

• increase in the percent service by public owned sewer systems and domestic wastewater treatment systems (Gappei-Jokaso (Jokaso to treat both night-soil and gray water), sewage systems for farming villages, community owned sewage treatment plants, etc.)

• regulation of industrial effluents according to TMDL standards

• advice and assistance to reduce pollution loadings from these industries

Contemporary regulations controlled the concentration of effluents at the point of discharge. The TMDL regulations, however, controls the maximum allowable daily loading from industries located in the specified basin and having a daily discharge of more than 50m³.

Specified effluents are effluents from specified industries except for waters without pollution loads like cooling water.

Water Pollution Control Law

• Effluent Pollution Control and Standards
• Application of Effluent Water Quality Standards and Designation of Specified Facilities
• Enforcement of Effluent Water Quality Standards
• Regulation of Total Maximum Daily Loading
• Promotion of Countermeasures against Domestic Effluents
• Water Quality Monitoring for Public Waters
• Countermeasures Against Groundwater Pollution
• Roles of Local Government in Water Quality Control
• Referneces : Effluent Water Quality Standards for the Sewage System