Land application of biosolids: benefits, risks and cost

Summarization: Governmental agencies, municipalities and industries around the world have been seeking viable alternatives for disposing of biosolids generated from wastewater treatment since landfill capacity diminishes and waste disposal costs increase. Biosolids are composed of compounds valuable for agricultural use (organic matter, nitrogen, phosphorous, potassium and micro-nutrients such as calcium, sulphur and magnesium), and pollutants that include heavy metals, organic compounds and pathogens. While they can be a valuable resource, potential risks associated with the nutrients, disease causing microorganisms, chemical contaminants and unstabilized material that biosolids include need to be appropriately managed. Alternative disposal methods for biosolids that have been used in the past include dumping at sea, landfilling, incineration and land application. The amount of generated sludge that needs to be disposed of in EU is exceeding 10 M dry tons per year while the US has to dispose approximately 7 M dry tons per year. Given that approximately half of the operating cost of waste water treatment plants is related to the treatment and disposal of sludge, the magnitude of treatment and disposal has promoted regulatory actions during the past 20 years focusing mostly on land application of biosolids and spurred the development of composting and other lower cost technologies that ensure not only their disposal, but also their reuse. The objective of this manuscript is to provide an overview of the potential benefits and risks of land application of biosolids with special emphasis on rural environments as well as on the management cost of disposal. Special focus will be given to sludges produced in rural areas such as the island of Crete and on closing the nutrient loop between urban and peri-urban areas. Sewage sludge has to be treated (dewatered and stabilized) before land application either in terms of soil fertilization or land reclamation. There are several treatment methods available: lime stabilization, composting, anaerobic digestion and thermal drying. Land application of biosolids has significantly positive effect on soil fertility ensuring their use in a sustainable manner. Their relatively high and readily available nutrient content has high fertilization value for the plants. In addition to the high nutritional value, biosolids improve the physico-chemical properties of the soil (soil conditioning) by increasing soil organic matter, decrease bulk density, increase soil particle aggregation, soil structure and porosity. Organic matter addition stimulates microbial activity and enzymatic production in the soil that are essential biocatalyst for plant growth. Finally, sludge amendments to agricultural lands have increased crop production and yields typically exceed inorganic fertilization yields. The risk associated with land application of biosolids depends on the origin of the pollution loads entering the waste water treatment plants (municipal versus industrial loads). Human and animal health, soil quality, plant growth and water quality can be seriously affected by uncontrolled pollutants and pathogens and excessive or improperly application of N and P that may be contained in biosolids. Excessive rates of land application can negatively impact groundwater quality because of nutrient leaching. However, this risk is substantially reduced if appropriate stabilization methods have been applied and risk bazed, site-specific land application loads have been incorporated in current regulations. This would be especially true in rural areas where the quality of sludges is of superior quality compared to major urban centres that have significant industrial contributions. The cost of treatment (both capital cost and operating cost) can be significantly reduced if we view sludge treatment and disposal as part of a holistic system of separation and recycling of organic matter from all sources (including solid waste -organic fraction recycling, agricultural wastes, livestock etc) in a urban-peri urban system and in this way closing the nutrient loop and returning the organic matter back to the cultivated soil, restoring in this way soil fertility.Παρουσιάστηκε στο: International Water Association, Wastewater Purification and Reus

Towards sustainable management of Mediterranean river basins: policy recommendations on management aspects of temporary streams

In 2011, the European Council stressed the significance of water quality for sustainable development in Europe and emphasized the need for better integration of the water policy objectives into the Common Agriculture Policy reform in rural areas. Since 2000, the Water Framework Directive (WFD) has required the EU Member States to target good ecological status for their water bodies. However, the implementation of the Directive for the numerous Mediterranean temporary streams has been delayed indicating the need for elaboration of the tools and methods that address the special characteristics of such water bodies. This requirement has been addressed by the recently completed MIRAGE project. In the context of the recent publication of the European Commission’s Blueprint to Safeguard Europe’s Waters, the MIRAGE-proposed framework for the characterization of the ecohydrological dynamics and the systematic description of the measured impact for temporary rivers could bring considerable added value to the EU revision of all relevant water policies. The project recommends additions to WFD articles including an explicit definition of temporary rivers, adaptation of environmental objectives to their peculiarities and establishment of a proper method to determine the initial status and specific actions in River Basin Management Plans

Innovative methodology for the prioritization of the Program of Measures for integrated water resources management of the Region of Crete, Greece

Summarization: An innovative multi-criteria methodology was proposed for the prioritization of the Program of Measures (PoM) in the Water Region of Crete, and applied specifically to the basin of Geropotamos river according to the requirements of the Water Framework Directive. This study relied on the four pillars of sustainability and the EU cross-compliance legislative objective for the minimization of the climate change impact. The multi-criteria evaluation methodology was based on the results of four different types of analyses: a DPSIR analysis, a SWOT analysis, a Cost-Benefit Analysis and a climate change impacts analysis. Public participation on the results of the study with local stakeholders was used at every stage of the multi-criteria evaluation process, from the selection and weighing of the criteria to the final ranking and measures' prioritization. The PoM contains two types of measures: basic measures which deal with the implementation of existing legislation and are the same for all regions of Greece and additional measures which are specified for the Region of Crete. The results of the prioritization process in Geropotamos Basin suggests that improving the water quality and ecological status of available water resources do not always require significant financial resources and can have a high impact in terms of achieving “good” quality status.Παρουσιάστηκε στο: Science of the Total Environmen