Determination of microbial contamination of urban runoff and reduction of microbial load using new column and biological batch filter design

Abstract

In this study first, amounts of coliform contamination were measured by sampling from urban runoff of Yasouj city, Iran. In order to designing column experiments, zeolite, anthracite, sand, iron filings, sawdust, geotextile and polyester fiber were used. In the next step, batch experiments were designed: PRB materials included 25% anthracite, 20% zeolite, 20% iron filings, 10% sawdust and 25% sand. This experiment was performed in two ways: with and without the availability of nutrients. For all experiments, E. coli used as biological contaminants and bacterial enumerations were done by MPN test. Amounts of coliform contamination in urban runoff were at the 93 to 1200 instance. The results of the column experiments showed that removability of these materials was 90.48 to 96.13% and materials saturated after operated for some time and it shows the phenomena detachment of pollutants. The results of batch experiment showed bacterial elimination 91.55–93.18% and detachment rate with and without nutrients 0.2% and 0.14% rate attachment respectively. Coefficients, growth rates, death rates, rates of attachment and detachment were 0.1396, 0.1633, 0.396 and 0.0555 per unit time, respectively. As a supplementary case, modeling of contaminant transport in the porous medium of a new biological filter was also investigated. Synthetic wastewater with an initial nitrate concentration of 100 mg/l is introduced to the filter over 25 minutes of the filter breakthrough curve (BTC). The BTC from the column test is assumed as a normal curve and the obtained longitudinal dispersion coefficient is equal to 1×10− 7m2/s.