Wastewater Treatment Sludge Management Plan (2017-2024)
The Plan covers the management of the sludge generated in the treatment plants of the Community of Madrid that receive urban wastewater, in septic tanks and in other wastewater treatment plants that treat water of a similar composition (mainly from the agri-food industry).
Sewage sludge is a mixture of water and solids resulting from the treatment of wastewater in purification facilities. Its composition is based on the quality of the wastewater at source and the purification system used, and determines the type of management to be applied and possible uses (mainly in agriculture).
This sludge is considered waste, both in its original state at the end of the wastewater treatment (solid/liquid mixture) and after being subjected to the appropriate treatments that can convert it into solid waste.
Madrid City Council, Canal de Isabel II, owners of wastewater treatment plants, companies that apply sludge, owners of agricultural land and waste managers.
- Waste prevention.
- Management measures.
- Inter-administrative coordination.
Since 2006 there has been a 30% reduction in the amount of sludge generated in the treatment plants of the Community of Madrid, despite the general increase in population in the same period. This is explained by the improvements in the treatment and dehydration processes of WWTP sludge and by the economic crisis of recent years.
98% of sewage sludge is generated in the Canal de Isabel II WWTP and the Madrid City Council. The remaining sludge is generated in treatment plants in large urbanizations and in industries from various sectors (mainly agri-food).
After subjecting the wastewater to the corresponding purification treatments, a semi-solid residue is generated in the WWTP, mainly composed of a mixture of water, organic matter and various elements, some of interest as agricultural amendments (mainly Ca, P, N, Fe, K and vegetable micronutrients) and other potentially contaminants such as heavy metals (fundamentally Cd, Cr, Cu, Hg, Ni, Pb and Zn), pathogens and organic contaminants. In WWTPs, the sludge generated is subjected to various treatments in order to achieve its stabilization, thickening and sanitization. In this way, its subsequent handling and management is facilitated.
As a result of the analysis and characterization of these sludges, their management is determined:
- Almost all of the sludge generated can be considered as non-hazardous waste and, therefore, can be managed as such.
- Almost all of the sludge generated has a low content of heavy metals, which is why it is suitable to be managed by applying it to agricultural soils, either by direct application, or after subjecting the sludge to a prior process of thermal drying or composting. .
- To carry out the treatment of the sludge, the Canal de Isabel II has a composting plant, thermal drying with cogeneration and a landfill located in Loeches. The sludge with a higher content of heavy metals, and therefore not suitable for agricultural use, generated at the Canal de Isabel II facilities is preferably used for energy recovery in facilities not established in the Community of Madrid, after treatment in the drying plant Loeches thermal plant (commissioned in 2010), and occasionally deposited in a controlled landfill for non-hazardous waste.
- For its part, the Madrid City Council has two thermal drying and cogeneration plants. The treated sludge generated in the WWTP owned by the Madrid City Council has been entirely used for application in agriculture, either directly or having previously been subjected to thermal drying.
- The management of sludge generated by other producers outside the Canal de Isabel II and the Madrid City Council has been carried out through its application in agriculture.
Of the total sludge generated, more than 98% is being applied in agriculture (material recovery), so it is considered that the current management is in accordance with the objectives of the State Framework Plan for Waste Management (PEMAR) 2016-2022.
Problems for the future:
- The agricultural area available to receive sludge is reaching its maximum.
- There are periods in which the application of sludge cannot be carried out due to weather conditions (rainfall and inadequate temperatures) or due to agricultural conditions.
- The inadequate application of sludge in agriculture can cause problems due to bad odors and the risk of contamination of groundwater or soil masses.
This problem can be minimized with the proper operation, monitoring and control of the sludge drying facilities, the implementation of temporary storage and good agricultural practices in its application.
Optimize the current management of the agricultural use of sludge with some complementary measures, aimed at reducing sludge contamination and improving its agricultural application, achieving adequate recovery of its organic matter content at an affordable cost.
The objectives to be achieved with the Plan are in line with the objectives established in the Waste Management Framework State Plan (PEMAR) 2016-2022:
- Improve the information system on sludge management.
- Apply the waste hierarchy increasing the prevention of wastewater and, consequently, the contamination of the sludge at source.
- Improve intermediate storage capacity, especially that of sludge intended for application to soils.
- Apply a final management model for wastewater treatment sludge that is environmentally appropriate and at affordable economic costs.
- Improve traceability and control of sludge, both for agricultural use and for incineration.
Quantitative objectives to be achieved in 2020:
- Recovery in soils and other types of recovery (excluding energy) of a minimum of 85% of the total sludge produced.
- Incineration/co-incineration and landfill disposal of a maximum of 15% of the total sludge produced (minimum 8% with energy recovery).
- Incineration/co-incineration (energy recovery) of at least 8% of the total sludge produced (percentage included in the objective of the previous section).
- Landfill disposal of a maximum of 7% of the total sludge produced (percentage included in the objective of the second section).
Activities to develop
- Control campaigns in industrial activities, especially in the areas of the Community of Madrid served by WWTP in which the limit values of contaminants in sewage sludge are exceeded.
- Reduction at source of contamination from wastewater discharges through pretreatment systems for industrial effluents, changes in processes or industrial raw materials, segregation of industrial effluents that require treatment as waste, as well as improvement in treatment systems for wastewater. purification sludge in the WWTP, taking into account the Best Available Techniques (BAT).
- Preparation of guides, codes and manuals of good practices aimed at the business sectors to promote the adoption of the Best Available Techniques and the improvement of the quality of their liquid effluents, especially with regard to the presence of metals.
- R+D+i programs to reduce pollution from industrial wastewater, treatment of sludge in WWTPs, drying or conditioning processes for sludge and new agricultural, industrial or energy applications.
- Promotion of the best techniques available in sludge sanitization and drying treatments.
- Promotion of the use of sludge in agricultural and forestry soils and reinforcement of inspection and control by the competent administrations.
- Construction of intermediate storage centers by managers and users, to avoid the temporary storage of sludge on the farms.
- Preparation of codes and manuals of good practices related to the use of sludge in agricultural soils.
- Implementation of a single registration system on production and producers of sludge, managers and agricultural users.
- Improve coordination between the different Administrations, the sludge management companies, the producers or operators of WWTPs and the owners of land suitable for the application of sludge in agriculture.
The implementation of the measures and actions contemplated in the Plan are budgeted between the Community of Madrid and private companies.
The Community of Madrid, with the support of Canal de Isabel II and the Madrid City Council, will address actions to control industrial liquid discharges, sludge treatment and its agricultural application, preparation of guides and manuals of good practices, promotion of use on agricultural and forest land, implementation of the single computerized system for the production and management of sludge, research and development programs on pollution reduction, improvement in the treatment of sludge in WWTPs, their conditioning, and new applications, both agricultural and industries, as well as inter-administrative coordination tasks and with the affected economic sectors.
The budget amount estimated to be necessary by the Community of Madrid for the period of validity of the Plan amounts to €110.000, to support the implementation of a single computer system on sludge production and management. This amount must be added to the budgeted measures such as transversal communication and R+D+i measures.
The execution and financing of the infrastructures to increase the temporary storage capacity will correspond to the managers or the owners of the lands on which they are applied.
Perception result indicators
For the continuous monitoring and evaluation of the Plan, the following indicators are expected to be used to analyze the degree of compliance with the objectives:
- Amount of sludge generated by the different entities that generate sludge (Madrid City Council, Canal de Isabel II, private urbanizations and agri-food industries).
- Percentages of the different final destinations of sewage sludge, calculated on the total amount of sludge produced.
- Compliance with the percentages established in the PEMAR objectives (2016-2022) in the management of sludge in terms of its agricultural recovery, energy recovery and landfill disposal.
- Agricultural land used for sewage sludge.
- Amount of sludge dried in energy facilities.
- Number of industrial activities with discharges to the integral sanitation system that have a Discharge Authorization.