Roxia treats difficult leachate and reject waters in Lappeenranta

Roxia Plasma Oy has been the reliable partner for Etelä-Karjalan Jätehuolto Oy (EKJH) for many years. EKJH is responsible for collecting and utilizing municipal waste of nine municipalities in the South Karelia region.

EKJH waste management facility has a new biogas plant that produces biogas from biowaste and municipal wastewater sludge. All wastewaters in the facility area are collected in an equalization basin before being pumped into the municipal sewage network and further to a municipal wastewater treatment plant. The wastewaters are from various sources including leachate from the close by landfill areas, reject water from the biogas plant and process waters from a composting facility. In the springtime, runoff meltwater has a considerable effect on the quality and quantity of the collected wastewater.

The biogas plant reject water has a very high load and is not acceptable to be treated in the municipal wastewater treatment plant as such. Therefore, the need for an agile on-site treatment process arose.

Having supplied other services such as aeration for the equalization basin, Roxia Plasma Oy was already familiar with the water management system and processes on the facility premises. Floating aerators keep the basin ice-free during winter and prevent odours during summertime.

We started to investigate a suitable solution with laboratory-scale testing. A process which transforms colloid solids into easily separable form with chemical treatment and subsequently separates the solids with flotation was found suitable. Economically feasible treatment removed over 90% of the load in the laboratory tests.

Real-life experiences with full-scale pilot

After the laboratory-scale testing, it was time to do a full-scale on-site pilot study. The pilot plant was built in sea containers and included transfer pumping, chemicalization, flotation and sludge dewatering units. The automated pilot plant was equipped with remote monitoring and control system. This kind of agile and fast commissioned pilot plant enables the demonstration of the treatment process on large scale and in different sites.

The pilot plant treated wastewater continuously and the cleaned water was led directly to the pumping station to be pumped to the sewer network. This enabled remediation of the challenging water situation already during the piloting phase. The results matched those of laboratory testing with over 90% reduction in load in continuous operation.

Roxia Floating Aerators keep the equalization basin ice-free during wintertime and the water treatment plant pre-treats wastewater to be eligible for municipal treatment.

Agile delivery and commissioning of a containerized wastewater treatment plant

The delivery and commissioning of the actual wastewater treatment plant took place at the beginning of 2022. The installation of the containers was quick and in addition, only the intermediate piping and electrical work were needed. After installation works the process start-up and adjustment could be done in one day. The automated process and continuous support from Roxia Plasma Oy ensure the continuity and effectiveness of the treatment even though the wastewater is a very challenging type and its quality and quantity vary hour by hour. Water leaving for the municipal wastewater treatment is now of considerably better quality and it is now acceptable for final treatment without problems. The sludge from the treatment process is pumped to the nearby composting facility.


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Lyle Henson

Sales Manager North America

+1 443 695 9510

Pyry Kupias

Technical Product Manager

+358 40 721 8919

Maija Mehto

Technical Account Manager

+358 50 534 3211