EFFECTIVENESS OF CONSTRUCTED WETLANDS FOR DAIRY WASTEWATER TREATMENT

There are 9 dairy facilities having their own wastewater treatment plants in Podlasie province. In majority, they were built in 70's of the 20th century, when "Promlecz" technology based on high and low-loaded sludge activated chambers dominated. According to data from 2008, the amount of disposed wastewaters is from 470 to 5200 m(3) . d(-1), at personal equivalent (P.E.) from 7130 to 277 000. Most of wastewater treatment plants requires to be modernized due to their poor technical status along with the increase of production, which is associated with the quantity of generated wastewaters, sludge, and reject water that should be processed. In the case of small treatment plants, the constructed wetland method may be an alternative for advanced and expensive technologies that are usually incorporated during modernization. Vertical and horizontal-flow wetlands can successfully work as a second stage of dairy wastewater purification after their preliminary mechanical and biological treatment. The study was carried out on a base of existing installation designed by the author and working in dairy wastewater treatment plant in Wysokie Mazowieckie. Studies were concentrated upon applying the hybrid system consisting of vertical-flow constructed wetland (VF-CW) and horizontal-flow constructed wetland (HF-CW). Wastewater after de-phosphatation and high-loaded sludge activated chamber were subjected to purification. Mean pollution concentrations in dairy wastewater taken to the researches were: BOD5 (234.1 mg O-2 . dm(-3)), COD (332.8 mg O-2 . dm(-3)), Kjeldahl's nitrogen (25.9 mg N-TKN . dm(-3)), ammonium nitrogen (13.9 mg N . dm(-3)), total phosphorus (10.9 mg P-T . dm(-3)). BOD5 removal efficiency was 84.8 %, Kjeldahl's nitrogen 81.0 %, ammonium nitrogen 91.0 %, and total phosphorus 39 %, on average. The study confirmed the usefulness of constructed wetland method applied after mechanical and biological stages at dairy wastewater treatment plants.