Oczyszczanie odcieków z beztlenowej stabilizacji osadów z oczyszczalni ścieków mleczarskich przy zastosowaniem metody hydrofitowej

The paper presents author's experience related to reject water treatment with constructed wetland (CW). CW technology is well known worldwide to treat municipal wastewater, rainwater and also industrial wastewater. The problem with reject water is mainly concerning high concentration of ammonia nitrogen. It is observed mainly in municipal WWTPs utilizing anaerobic sewage sludge stabilization. Dairy WWTP belonging to Mlekovita was modernized in 2013 with implementation of flotation process in wastewater line and anaerobic stabilization of excess and flotation sludge. Probably this is the biggest dairy WWTP in Poland. It is operating (July 2014) with 6886 m3/d and personal equivalent about 278 000 (project was done for PE 35 0000 and maximum flow 75000 m3/d). Reject water as a byproduct like sewage sludge is returned to the beginning of wastewater line. During own research with reject water it was found that concentration of ammonia nitrogen was varied from 291 N-NH4+/dm3to 423 mg N-NH4+/dm3. while value of BOD5 from 132 to 185 mg O2/dm3. Laboratory scale investigation was carried out with vertical flow CW model with total depth 0,65 m. filled with gravel and sand. Two hydraulic loads were applied during investigations – 0,1 and 0,2 m/d. The temperature during two series was changing from 22,0 do 26,0°C. High efficiency of BOD5 removal (up to 91%) from reject water produced in dairy WWTP was observed. The efficiency of ammonia nitrogen removal was varied from 78,3% to 90,0%. The efficiency of total phosphorus removal was low in both series. Vertical flow constructed wetland can be used as a low cost method to decrease load of dairy WWTP utilizing anaerobic sewage sludge utilization. To increase efficiency of reject water treatment lower hydraulic load (from 0,05 m/d) should be applied. Future researches will be carried out with real scale installation in Wysokie Mazowieckie equipped with special aeration system to supply vertical flow CW with oxygen.