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Council Directive 91/271/EEC on Urban Waste Water Treatment: Provisions Overview
Article 1: Objective
This Directive addresses the collection, treatment, and discharge of urban waste water, as well as the treatment and discharge of waste water from specific industrial sectors. The primary objective is to protect the environment from the adverse effects resulting from these waste water discharges.
Article 2: Definitions
- Urban Waste Water: Domestic waste water or a mixture of domestic waste water with industrial waste water and/or rain run-off.
- Agglomeration: An area with a sufficient concentration of population and/or economic activities for urban waste water to be collected and directed to a treatment plant or discharge point.
- Collecting System: A network of conduits that collects and conveys urban waste water.
- Population Equivalent (1 p.e.): Represents an organic biodegradable load with a five-day biochemical oxygen demand (BOD5) of 60 grams of oxygen per day.
- Secondary Treatment: Treatment process generally involving biological treatment with secondary settlement, meeting the requirements specified in Table 1 of Annex I.
- Appropriate Treatment: Any treatment process or disposal system that ensures the receiving waters meet relevant quality objectives and comply with this Directive and other Community Directives.
- Eutrophication: Nutrient enrichment of water, especially nitrogen and phosphorus compounds, leading to excessive growth of algae and plants, disrupting aquatic ecosystems and water quality.
Article 4: Treatment Requirements Before Discharge
Member States must ensure that urban waste water entering collecting systems undergoes secondary treatment or equivalent treatment prior to discharge, according to the following deadlines based on the size of the agglomeration:
- By 31 December 2000 for all discharges from agglomerations exceeding 15,000 p.e.
- By 31 December 2005 for all discharges from agglomerations with populations between 10,000 and 15,000 p.e.
- By 31 December 2005 for discharges to fresh water and estuaries from agglomerations with populations between 2,000 and 10,000 p.e.
Additionally, discharges from these treatment plants must comply with the relevant requirements of Annex I.B. The population equivalent load is calculated based on the maximum average weekly load entering the treatment plant during the year, excluding unusual situations such as heavy rainfall.
Article 5: Stringent Treatment in Sensitive Areas
Member States must ensure that urban waste water entering collecting systems is subject to more stringent treatment before discharge into sensitive areas or their catchment areas. The deadlines for achieving this more stringent treatment are:
- By 31 December 1998 for all discharges from agglomerations exceeding 10,000 p.e.
Discharges from these treatment plants must meet the requirements of Annex I.B. Alternatively, in sensitive areas where it’s demonstrated that there’s at least a 75% reduction in total phosphorus and nitrogen loads across all urban waste water treatment plants in the area, individual plant requirements under this Article may not apply. Additionally, discharges from treatment plants located in the catchment areas of sensitive areas must adhere to these stringent treatment requirements.
Areas identified as sensitive must comply with these requirements within seven years of their identification.
Article 10: Performance of Treatment Plants
Member States must ensure that urban waste water treatment plants designed to comply with Articles 4, 5, 6, and 7 are adequately designed, constructed, operated, and maintained to ensure sufficient performance under all normal local climatic conditions. This includes accounting for seasonal variations in waste water load during the design phase.
Article 15: Monitoring and Compliance Verification
Competent authorities or appropriate bodies are required to monitor discharges from urban waste water treatment plants to verify compliance with Annex I.B. This monitoring must adhere to the control procedures specified in Annex I.D. Specifically:
- Monitoring must ensure that discharges meet the quality standards outlined in Annex I.B.
- Control procedures in Annex I.D detail the methods and frequency of sampling and analysis.
- There is a maximum allowed number of samples that may fail to meet the specified requirements within a given monitoring period.
Failure to adhere to these monitoring requirements constitutes a breach of Article 15 and the associated annexes.
Annex I: Requirements for Urban Waste Water
Section B: Discharge Requirements
Details the quality standards that treated urban waste water must meet before being discharged into receiving waters. This includes limits on pollutants such as chemical oxygen demand (COD) and biochemical oxygen demand (BOD5).
Section D: Reference Methods for Monitoring and Evaluation
Outlines the approved methods for monitoring and evaluating the quality of discharges from urban waste water treatment plants. It specifies sampling frequency, analytical procedures, and criteria for evaluating compliance based on the collected data.[:]
