# Municipal Sewage Sludge Disposal in the Republic of Poland
## 5 Methods of Disposal of Sewage Sludge
### Composting  
One of the methods of processing municipal sewage sludge is composing. According to the provisions of the Act on Waste Pole [23], this is a recovery process using the R3 method. In the process of composting municipal sewage sludge, the aim is to destroy pathogenic organisms, stabilize organic matter (maturing), dry it, and produce a material that can be used for agriculture or sold. For this purpose, the sewage sludge must be mixed with structure-forming materials in the appropriate proportion to obtain a C:N ratio of approximately 30:1. In practice, construction materials containing cellulose are most often wood chips, sawdust, bark, straw, and leaf litter [45]. The process produces a final product, compost. Compost improves the soil's physical, chemical, and biological properties, such as organic matter, water and nutrient retention capacity, infiltration, aeration, compaction and erosion resistance, and soil-borne diseases [46, 47, 48]. Compost promotes the development of soil macrofauna, which plays an important role in improving soil quality. In addition, compost slowly releases nutrients that plants can take up, thus contributing to enhanced crop productivity. Compost contains macronutrients (mainly nitrogen, phosphorus, and potassium) and micronutrients essential for plant growth; so, its use improves soil fertility. Compost stimulates microbial activity, thereby increasing the availability of nutrients to plants and producing hormone-like substances that can contribute to crop growth. It is widely used in agriculture, horticulture, viticulture, forestry, urban landscapes, and greenhouses [46, 47, 48, 49]. It can be used for shaping green areas, municipal and forest management, construction and maintenance of embankments of communication routes, construction of acoustic screens, and reclamation and covering of landfills. Composing, as a method of processing municipal sewage sludge, is a beneficial technology for sewage treatment plants in rural areas. Municipal sewage sludge contains low concentrations of heavy metals caused by the lack of industrial sewage flowing into the treatment plant through the sewage system. The compost obtained can be used for agricultural purposes to obtain a fertilizer certificate, as is the case at the sewage treatment plants in Shupsk, Nova Wies Elcka, Pila, and Sokolka. Since 1996, a composting plant for biodegradable waste, including stabilized municipal sewage sludge with green waste, has been operating at the Sewage Treatment Plant in Shupsk. The composting plant covers an area of 1.5 ha, of which 0.91 ha is roofed. It has a hardened surface as a reinforced concrete slab placed on the ground with a compost pile aeration system, a leachate drainage system, and a deodorization system. This facility is adapted for the biological processing of approximately 20,000 tons/year of waste subject to aerobic decomposition with the participation of microorganisms, including approximately 13,000 Mg/year of sewage sludge operating using the technology of a shifted heap. The remaining part consists mainly of structural waste obtained from other producers in the form of straw, branches, and bark. As a result of aerobic decomposition processes with the participation of microorganisms, a full-value product is created--a compost called \"BIOTOP\", which is admitted to circulation and has the status of organic fertilizer. In composting plants, approximately 7000 Mg/year of compost are produced from 20,000 Mg/year of waste raw materials [50]. Another example of municipal sewage sludge processing into full-value compost is the Sewage Treatment Plant in Nova Wies Elcka. Compost production is based on turning a pile, the so-called additional method involving recirculating the hot phase. Fermented and mechanically dewatered municipal sewage sludge mixed with straw, wood chips, and inoculum from the pile in the hot phase is used for composting. The product obtained this way is a fertilizer called \"Kompelk\", which used to grow cereals and establish lawns [51].