Research of methods for the waste water sluge treatment technology of Petrozavodsky treatment facilities

In large Russian settlements, including settlements in Karelia, the problem of treating sewage sludge has not yet been solved or has been partially solved. Existing sludge treatment schemes are often not efficient and do not correspond to the best available technologies. As a result, waste disposal facilities are congested with sludge and huge areas for sediment storage are withdrawn from public use. The sludge itself, as a valuable product, remains unclaimed forever. Industrial effluents from Petrozavodsk account for 10 - 20% of the total urban wastewater discharge. The effluent is discharged into the Petrozavodsk Bay of Lake Onega in an average volume of 130,000 m3 / day. Approximately, the volume of formation of dehydrated sludge is 13 000 - 16 000 tons / year. The most popular wastewater sludge treatment options are composting in open piles and composting with preheating; chemical stabilization; thermal drying; burning. From the point of view of capital costs and operating costs, the method of composting in open piles is defined as cost-effective. The other technology options under consideration provide a higher level of sediment stabilization and are characterized by a lower need for areas, but the capital costs for their implementation and operating costs are higher than for the open composting technology. The sediment consumption for composting is 600 - 700 cubic meters per sludge site per month. One year research showed that the dynamics of temperature indicators did not reveal differences in temperature between compostable mixtures embedded in the summer, winter and demi-season periods of the year. The sludge is mixed with bark in a ratio of 1: 1 by weight of the dry matter content. Also, the treatment process can be intensified by supplementing it with a mixing system and preliminary heating of the soil, which provides the required level of compost disinfection. At the same time, the compost ripening period is reduced by 3-4 months. The resulting soil is implemented during the improvement of urban areas. Analysis for the presence of heavy metals and radioactive elements showed that their maximum allowable concentrations have not been exceeded.