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Julita Milik, Rafał Pasela, Marek Szymczak, Mariusz Chalamoński
Uniwersytet Technologiczno-Przyrodniczy, Bydgoszcz

Abstract
Municipal sewage sludge are a by-product of waste water treatment. The problems of sludge associated with the development of sludge require urgent solutions. Municipal sewage sludge may be used in agriculture in two forms: processed and unprocessed if they are stabilized and comply with acceptable levels of heavy metals and sanitation indicators and include the relevant product quantities of organic compounds and fertilizing nitrogen, phosphorus and potassium. Composition and quantity of sludge produced in the wastewater treatment process is different and depends on several parameters such as quality of waste water and processes for their purification. The presents shows an assessment of the physical and chemical sludge from sewage treatment plants selected and the results of research and analysis for the sludge collected from said object. Analysis of the results was carried out for possibilities to use sewage sludge for agricultural purposes. Sewage sludge derived from a sewage treatment plant mechanical-biological stabilization of sludge anaerobic digestion with a capacity of 26,400 m3 per day. The sediment samples were collected in the period from January to September 2015 year with a two-month interval. Attempts were subjected to microwave mineralization in a closed system in aqua regia. The heavy metal concentrations determined with a spectrophotometer Coupled Plasma emission ICP-OES Perkin-Elmer Optima 8000 detecting elements P, Ca, Mg, Pb, Cd, Hg, Ni, Zn, Cu, Cr. The collected sediment were determined: pH, dry weight of sediment, organic matter (marked as loss on ignition at 550 ° C), total nitrogen (Kjeldahl) and ammonium nitrogen. The results were compared with the limit values according to the law. It has been shown that the predominant heavy metals present in the sludge was copper and zinc, mercury was not detected. The value of organic matter sludge tested ranged from 49.36 to 63.15% of dry matter. The content of heavy metals in sediments was measured by reference to the existing provisions governing the use of natural sewage sludge. The contents of heavy metals were low and did not exceed the limit values in sewage sludge for their use in agriculture and land reclamation. The studied sediments were stable nature. The results indicate the good properties of the sludge, which can be used as organic fertilizer. It has been shown that the sludge produced in the study treatment did not exceed in any case permissible concentrations of heavy metals specified for sewage sludge used for agricultural purposes. The annual average content of heavy metals in the study period remained at a similar level. Understanding the composition of the physico-chemical sludge waste is the basis for the decision over their processing, use or disposal. The precipitate may be disposed by using thermal methods for combustion of solid comprising 90% of dry matter.

Słowa kluczowe
osady ściekowe, skład chemiczny, metale ciężkie, substancja organiczna, oczyszczanie ścieków komunalnych

Evaluation of the Physico-chemical Composition of Sludge from Municipal Sewage Treatment Plant

Key words 
sewage sludge, chemical, heavy metals, organic material, waste water treatment

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