Improvement of the parameters of constructed wetlands filter when applying it for the treatment of dairy wastewater

Abstract

This study investigated the suitability of sand reed filter for the treatment of waste water from milk collection post and on the basis of the studies performed to determine the minimal length of filtration path in order to reach the normative waste water treatment level. In 2003, in Padargupiai village (Ariogala municipality, Raseiniai district in Lithuania) experimental treatment facilities for waste water from milk collection post were constructed. As the pollution of such waste water after pre-treatment (primary treatment) is 2 times higher than that of domestic waste water, the filtration path in constructed wetlands was made 2 times longer (up to 10 long). On the basis of the study results the dependence equations were made, with the help of which the amounts of the main pollutants contained in waste water of milk collection posts were calculated, after the waste water is filtered through the sand layer of different length. As calculations have shown, the treatment of waste water from milk collection posts until the allowable rates depends on the constructed wetlands with the length of the filtration path of 7. The removal of organic pollutants, total nitrogen and total phosphorus from waste water flowing through such media are 97.2, 68.7, and 91.0% respectively. The studies performed allowed to improve the calculations of the necessary area of constructed wetlands in order to reach the normative treatment level of waste water from milk collection posts according to the index biochemical oxygen demand (BOD5).