Biological pilot treatment reduces physicochemical and microbiological parameters of dairy cattle wastewater.

ABSTRACT

The objectives of the present study were to characterize and evaluate a pilot treatment unit (PTU) for dairy cattle wastewater (DCW) in relation to its efficiency in reducing the physicochemical and microbiological parameters and possible application of this fertilizer in organic production. A PTU was set up, composed of the following elements a dung pit of 7.8 m3, already in place; a septic tank; a set of anaerobic biological filters comprising an upflow filter and a downward-flow filter filled with fragments PVC corrugated conduit; and two constructed wetland systems (CWSs) of horizontal subsurface flow in two parallel routes (Routes 1 and 2), controlled by means of a flow rate divider box. Route 1 passed through CWS 1 cultivated with cattail (Typha domingensis) and Route 2 passed through CWS 2 cultivated with vetiver grass (Chrysopogon zizanioides). To evaluate the treatment stages, biweekly investigations were carried out to collect effluent samples. The results of monitoring, in absolute values, were evaluated by means of the medians and variation coefficients and compared by means of Kruskal-Wallis non-parametric test followed by the Student Newman Keuls test. The treatment efficiencies of Routes 1 and 2 were calculated. The influence of vetiver on the removal of nutrients from the DCW was analyzed and the productivity estimate (t.ha-1) was performed. CWS 1 was not able to reduce the organic load indices, but it was able to retain fatty material and sodium. CWS 2 showed a reduction in nitrogenous forms and also for other nutrients, achieving the greatest removal of sodium and greatest decay of fecal contamination indicators, thermotolerant coliforms (56.13%), and E. coli (46.82%).