Alternative methods in tracking sources of microbial contamination in waters

A key factor in the management and remediation of impaired ground- and surface water is the ability to distinguish the sources of faecal contamination. Several approaches have been adopted as microbial source tracking methods (MST), which are generally classified as culturing, phenotypic, genetic, and chemical MST. None of the techniques used thus far can be considered a standard; important factors, such as the statistical correlation between the source and the faecal indicator and the understanding of the environmental fate of the faecal pollutants, still need attention. The most promising MST methods available today are based on the genetic fingerprinting of faecal micro-organisms. However, research is very active also in the investigation of pharmaceuticals and personal care products discharged in the environment together with faecal waste. An updated overview of MST methods to distinguish human from animal sources of faecal pollution is presented here, focusing particularly on the potentialities of new chemical tracers

Biological conversion of sulfide to elemental sulfur

202-210<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">The use of a biological reactor (bioreactor) as a means of removing hydrogen sulfide from waste water and converting it to elemental sulfur has several advantages over conventional physical/chemical treatment processes. A suspended-growth continuous-flow stirred-tank bioreactor utilizing the green sulfur bacterium Chlorobium limicola was successfully operated at five different sulfide loading rates and three different hydraulic retention times. In all but one of the five experiments, the rate of consumption of the sulfide was equal to its loading rate. The separation of elemental sulfur from the bioreactor contents is essential to realize its value as a chemical industry feedstock. Separations of elemental sulfur by plain settling, settling at elevated p<span style="font-size:11.0pt;line-height: 115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:arial;mso-ansi-language:="" en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa;mso-bidi-font-style:="" italic"="">H, <span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">filtration and centrifuging were tested at bench scale using the contents of several batch bioreactors. Under plain settling, elemental sulfur and bacteria were removed from suspension to the same degree. Raising the <span style="font-size: 11.0pt;line-height:115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:="" minor-latin;mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:="" minor-fareast;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:arial;="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">pH to <span style="font-size:11.0pt; line-height:115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:arial;mso-ansi-language:="" en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">8.6 or <span style="font-size:11.0pt; line-height:115%;font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;="" mso-fareast-font-family:"times="" new="" roman";mso-fareast-theme-font:minor-fareast;="" mso-hansi-theme-font:minor-latin;mso-bidi-font-family:arial;mso-ansi-language:="" en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">8.8 resulted in some of the sulfur or bacteria settling independently of the sulfur-bacteria floes. Filtration was found to give conflicting results with different batches of bacteria. Centrifugation resulted in the best separation between elemental sulfur and bacteria; 90% of the elemental sulfur and 29% of the bacteria could be removed from suspension.</span

Evaluation of microbial indicators for the determination of bacterial groundwater contamination sources

Several different Microbial source tracking methods (MSTs) can be used to distinguish human from animal fecal contamination in water; In this study, experiments were carried out to test the effectiveness and reliability of three bacteria based approaches (the fecal coliforms to fecal streptococci ratio, antibiotic-resistant Clostridium perfringens, and human bifidobacteria) in a simulated groundwater micro-environment.The methods were evaluated in three phases: initially, the specificity of each indicator was validated on groundwater samples affected by known pollution source; then the variation of performance with time of each method was determined, and finally, the die-off coefficients for pure species of Clostridium perfringens and Bifidobacterium adolescentis were measured.The results indicate that only the determination of human bifidobacteria concentration can be considered reliable in distinguishing human from animal pollution in groundwater at the conditions applied. Nevertheless, human bifidobacteria were detectable only for two weeks after the contamination event. This study also shows that antibiotic resistant Clostridium perfringens detected using the Shahidi-Ferguson medium is not source specific, whereas it confirms that this species can be useful for timing general fecal contamination events