Experience in dewatering of municipal wastewater sludge with multi-disc screw press dehydrators. Example of Chornomorsk Vodokanal, Ukraine Public Utility Provider

Wastewater treatment plants, which are inferior to Chornomorsk Vodokanal, are the most important environment-related objects of the city of Chornomorsk. Their work directly affects the health of the city inhabitants, the attractiveness of the region as a tourist center, which in turn affects the replenishment of the city budget with tourism revenue.

Wastewater treatment plants have been put into operation since 1977 and after 40 years of continuous operation both the equipment and the technology itself have become morally and physically obsolete.

To renovate and modernize the structures, the city applied for inclusion in the Program for the development of municipal infrastructure of Ukraine, which was implemented at the expense of a loan from the European Investment Bank. After 2 years of hard work, the city was forced to withdraw from the Program due to unfavourable loan terms. Nevertheless, co-operation with the Bank and the European experts was not in vain. Based on European experience, the representatives of the Public Utility Provider have developed their own program, which appeared to be much cheaper than the concept proposed by the Western experts. With the support of the city’s Executive Committee the water and sanitation authority started the reconstruction of the main buildings and replacement of equipment in the state of disrepair. As part of the reconstruction, a mechanical dehydration plant was put into operation at the treatment facilities. The plant is the most important wastewater processing stage and the facilities have been operating without it for over 40 years.

Previously, the company practiced depositing untreated sludge in sludge lagoons. This outdated method had a negative impact on the environment in the region, and Chornomorsk Vodokanal was one of the first large water utilities in Ukraine which started using modern progressive and efficient methods of sludge treatment. Today, a mixture of wet sediments and excess sludge is processed in a new dehydration plant based on MDQ multi-disc screw press dehydrators. This type of equipment has been manufactured at the plant of the Ukrainian company Ekoton, under the license of Tsurumi, Japan, since 2011. During this time, Ekoton Industrial Group has successfully implemented more than 100 projects based on such dehydrators in the United States, European Union, Israel, the CIS countries and Ukraine.

The innovative Japanese technology has proven itself worldwide as a reliable and highly efficient solution for sludge dewatering. The use of dehydrators reduces the amount of sludge by about 20 times, which significantly reduces the cost of its transportation and disposal.

Besides the above the multi-disc screw press dehydrators are characterized by optimal price-quality relationship, high level of automation, low operating costs for electricity, reagents and flushing water and high productivity. All these factors influenced the choice of Ekoton equipment.

Thanks to the strengthened screw and its low rotation rate, the dehydrator can dehydrate even abrasive materials without the need to replace the discs and screw at least within 5 years. Another possible application of such dehydrators is dehydration of fat-containing sludge because such sludge does not clog the filter drum due to a special self-cleaning mechanism.

The use of new equipment not only allowed achieving the highest technological efficiency of the process but also optimizing significantly the dehydration plant service quality, while all systems have a high level of automation which will make it possible to operate the plant in fully automatic mode in the future and will not require the constant presence of the staff.

The productivity of this dehydration plant is 20 m3 per hour or 216 kg of dry matter per hour. The residual moisture content in the dehydrated sludge reaches 72-80% at an exceptionally economical average dose of flocculant of 3 kg/t of dry matter in the sludge. Energy consumption is 5 kW per hour for the whole set of equipment or 0.25 kW/m3 of sludge, and the consumption of flushing water is only 99 liters per hour.

Currently, the Public Utility Provider plans to compost the dehydrated sludge and use it further as fertilizer for industrial crops.