engleski

Elimination of coliform bacteria from municipal wastewater by "Green technology"

A pilot constructed wetland ("Green technology") of the surface of 125 m2 has been built in the village Hrušćica near Zagreb in October 2003. The constructed wetland receives a raw municipal wastewater. After primary settlings, the main flow is divided into tree treatment lines. The first line is planted with Typha latifolia and Scirpus sylvaticus, the second line is planted with Phragmites australis and Scirpus sylvaticus and the third line is not planted and serves as a control line. The goal of this study was to determine the elimination of faecal coliform bacteria (FC) and total suspended solids (TSS), as well as the decrease of biological oxygen demand within 24 h (BOD1) in the water of the horizontal profile of pilot constructed wetland. Moreover, the relation between these tree parameters was estimated. Analyses were conducted from Mart, 21 to May, 28 2004 (n=15). The high FC load in the influent wastewater (4.87 7.18 x 109 MPN/L) decreased in the effluent of the first line for 99.99%, second line 99.92% and control line 99.88%. The BOD1 of 62.88 62.89 mg O2/L in the influent decreased in the effluent for 91.41% in the first line, 89.51% in the second line and 90.30% in the control line. The TSS in the influent (61.60 22.51 mg/L) decreased in the effluent for 78.08% in the first line, 78.73% in the second line and 78.08% in the control line. A good performance of the control line is explained by the high adsorption capacity of the still unsaturated material that fills the bead of the wetland. The abundance of FC significantly positively correlated with the BOD1 (r=0.420, p=0.001) and TSS (r=0.409, p=0.001). The BOD1 also showed significant positive correlation with TSS (r=0.716, p=0.000). From the results it can be deduced that the FC population is responsible for much of the oxygen consumption in constructed wetland system. Moreover, much of the TSS in water can be described to the presence of live FC population. According to the data available, it seems that the elimination of FC, TSS and BOD1 in the examined pilot constructed wetland performs simultaneously.

coliform bacteria; municipal wastewater; constructed wetland

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