Sewage Sludge Management and its Possible Trends in Estonia

Estonian legislation in the area of environmental protection has followed EU directives and there are no discordances between them. The quality of sewage sludge has to be controlled and samples taken correspondingly. Only attested persons shall take the sludge sample.Approximately 550 000 m3 sludge per year is produced contains ca. 24 000 tons dry solids. In the year 2000 the utilisation of sewage sludge in urban landscaping, agriculture, horticulture and land restoration was 31 640 m3 of total. In addition ca. 46 700 m3/y is hauled to landfills. The concentration of heavy metals in the sewage sludge from the Estonian treatment plants is below the specified limits and therefore the land application of sludge could have been larger than at the present time. The residual sludge is held at the sites of wastewater treatment plants, composting places, is deposited in biological ponds and other artificial water bodies. A number of shortcomings and problems exist in sewage sludge disposal. A vision for Estonia, how the sludge disposal should be carried out, is presented. With the on-site and small wastewater treatment facilities when local sludge treatment is troublesome, expensive or impossible, sludge has to be hauled for treatment into bigger treatment plants. This is not a good solution and should be avoided. Simplified wastewater and sewage sludge treatment scheme is suggested for small (up to 2000 PE) treatment plants in rural areas. The technological concept for the scheme arose from practice and it is applicable under conditions where sufficient land is available to establish the biological ponds. Advantages of the suggested technological scheme are as follows: a) a high operator competency is not needed; b) process is technologically simple; c) sludge treatment is not expensive; d) wastewater treatment is stable. Disadvantages of proposed technological scheme are as follows: a) treatment complex needs biological ponds with proper layout, which is not often the case by the existing ponds; b) quality of treated water is not so high as in the case of the more complex treatment plants.