ANALYSIS OF COMPOSTED SLUDGE AT BIRŽAI SEWAGE TREATMENT PLANT
Keywords:wastewater sludge, sludge quality, composting, use of compost.
The article discusses the most important and efficient ways to use a sludge. The main goal of the research is to select the optimal method of sludge use in Biržai wastewater treatment plant, taking into account technical, economic and environmental factors. To achieve the goal, the quantities and the quality of a sludge accumulated at Biržai NV were systematized and evaluated. After analyzing the sludge research reports in 2015 and 2021 according to the concentration of heavy metals, the sludge has met category I and after calculating the quantities of accumulated sludge, it was found that from 2013 to 2021, 3 845 t of sludge was composted at the Biržai wastewater treatment plant. After evaluating the quantity and quality of sludge, alternatives for the use of sludge were selected. Technical, economic and environmental data on 6 potential uses of sludge have been collected and summarized, as well as other information describing the use of sludge. The task is multi-objective, covering both quantitative and qualitative criteria, therefore the method of multi-criteria decision analysis was chosen to solve it. The DAM program established that fertilization, energy forestry, and recultivation are the most efficient uses of sludge. Fertilization energy forests with compost would reduce the losses of Biržai NV compared to the alternatives examined in the study.