Tālis Juhna

Detection of Escherichia coli in Biofilms from Pipe Samples and Coupons in Drinking Water Distribution Networks

ABSTRACT Fluorescence in situ hybridization (FISH) was used for direct detection of Escherichia coli on pipe surfaces and coupons in drinking water distribution networks. Old cast iron main pipes were removed from water distribution networks in France, England, Portugal, and Latvia, and E. coli was analyzed in the biofilm. In addition, 44 flat coupons made of cast iron, polyvinyl chloride, or stainless steel were placed into and continuously exposed to water on 15 locations of 6 distribution networks in France and Latvia and examined after 1 to 6 months exposure to the drinking water. In order to increase the signal intensity, a peptide nucleic acid (PNA) 15-mer probe was used in the FISH screening for the presence or absence of E. coli on the surface of pipes and coupons, thus reducing occasional problems of autofluorescence and low fluorescence of the labeled bacteria. For comparison, cells were removed from the surfaces and examined with culture-based or enzymatic (detection of β-d-glucuronidase) methods. An additional verification was made by using PCR. Culture method indicated presence of E. coli in one of five pipes, whereas all pipes were positive with the FISH methods. E. coli was detected in 56% of the coupons using PNA FISH, but no E. coli was detected using culture or enzymatic methods. PCR analyses confirmed the presence of E. coli in samples that were negative according to culture-based and enzymatic methods. The viability of E. coli cells in the samples was demonstrated by the cell elongation after resuscitation in low-nutrient medium supplemented with pipemidic acid, suggesting that the cells were present in an active but nonculturable state, unable to grow on agar media. E. coli contributed to ca. 0.001 to 0.1% of the total bacterial number in the samples. The presence and number of E. coli did not correlate with any of physical and/or chemical characteristic of the drinking water (e.g., temperature, chlorine, or biodegradable organic matter concentration). We show here that E. coli is present in the biofilms of drinking water networks in Europe. Some of the cells are metabolically active but are often not detected due to limitations of traditionally used culture-based methods, indicating that biofilm should be considered as a reservoir that must be investigated further in order to evaluate the risk for human health.

Formation of biofilms in drinking water distribution networks, a case study in two cities in Finland and Latvia.

The formation of biofilms in drinking water distribution networks is a significant technical, aesthetic and hygienic problem. In this study, the effects of assimilable organic carbon, microbially available phosphorus (MAP), residual chlorine, temperature and corrosion products on the formation of biofilms were studied in two full-scale water supply systems in Finland and Latvia. Biofilm collectors consisting of polyvinyl chloride pipes were installed in several waterworks and distribution networks, which were supplied with chemically precipitated surface waters and groundwater from different sources. During a 1-year study, the biofilm density was measured by heterotrophic plate counts on R2A-agar, acridine orange direct counting and ATP-analyses. A moderate level of residual chorine decreased biofilm density, whereas an increase of MAP in water and accumulated cast iron corrosion products significantly increased biofilm density. This work confirms, in a full-scale distribution system in Finland and Latvia, our earlier in vitro finding that biofilm formation is affected by the availability of phosphorus in drinking water.

Purification of Contaminated Water with Chromium (VI) Using Pseudomonas aeruginosa

A bacterial strain Pseudomonas aeruginosa isolated from an uncontaminated soil has been used for the removal of hexavalent chromium (Cr (VI)). The experiments were carried out in batch system in a culture broth. The results obtained have shown that 100% of Cr (VI) are removed. Contact time, initial concentration of the hexavalent chromium, temperature, as well as the nature of the culture broth have influenced this elimination. To the initial concentration of 20g/L of Cr (VI) the elimination rates are lower, while the reverse occurs for an initial concentration of 8g/L. This study allows considering the use of Pseudomonas aeruginosa in the treatment of water polluted by toxic heavy metals such as Cr (VI).

Removal of phenols-like substances in pharmaceutical wastewater with fungal bioreactors by adding Trametes versicolor

Fungi are known to be more resistant to toxic compounds and more effective in removing recalcitrant organics such as phenols than bacteria. Here we examined the removal of phenols (as a component of Zopliclone drugs), added to non-sterile pharmaceutical wastewater with continuous treatment fungal bioreactor by its augmentation with mono-species of white-rot fungi (WRF) Trametes versicolor. Results showed that WRF in a sterile reactor (a batch mode) were moderately effective for removal of phenols (40% in seven days); however, native wastewater microbes at optimal conditions for fungi (pH 5.5, 25 °C) were more effective (90%, both in batch and continuous flow modes). In continuous flow mode, addition of WRF was an effective way to mitigate high loads of phenols (up to 400 mg/L), by both fungal enzymes (growth rate 0.075 h-1, laccase enzymatic activity 4 nkat/mL) and biosorption. The study confirmed that naturaly occuring fungi in combination with fungus-augmentation is an effective approach for treatment of high-strength pharmaceutical wastewater.

Review on Challenges and Limitations for Algae-Based Wastewater Treatment

Abstract Microalgae biomass production is recognized as a cost-effective and sustainable alternative to currently used approaches to tertiary wastewater treatment. However, such limitations, as algae biomass separation from water, process efficiency in cold climate and the algae biomass ability to reduce micropollutant content in wastewater hamper this method from full-scale use. This review discusses the identified drawbacks and offers possible improvements and modifications for wastewater phycobioremediation.

Alkaline Activated Material as the Adsorbent for Uptake of High Concentration of Zinc from Wastewater

The use of wastes for developing of new materials is a sustainable approach. In current study filter media produced from industrial waste was tested for an ability to decrease high concentration of zinc in standard solution and industrial wastewater. The geopolymer production requires mixing of post-industrial waste with naturally occurred aluminosilicate materials by using binding agent at the ambient or slightly increased temperature in order to produce a long lasting eco-friendly cementitious material. The tested media decreased concentration of zinc in standard solution from 72,9 to 19,6 mg/L in 30 min showing similar performance as commercially available zeolite material. In experiments with wastewater the adsorption of Zn by AAM was much lower, which can be explained by the fact that wastewater contained generous amounts of different metal ions, organic substances and oils. Despite complex composition of wastewater AAM was able to immobilize at minimum 22 mg/L (32%) Zn from the solution.

Electrochemical Drinking Water Disinfection with TiO2-x Ceramic Electrodes at Flow Conditions

Electrochemical disinfection device EDI-001 equipped with titanium oxide (TiO2-x) ceramic electrodes was tested as a system for direct treatment of drinking water at flow conditions. Laboratory experiments were conducted to estimate the disinfection efficiency and main system parameters. Escherichia coli was selected as the model microorganism. The results have shown that contaminated tap water was completely disinfected within 15 minutes by using EDI-001.

Latvian Practices for Protecting Water and Wastewater Infrastructure

The Republic of Latvia has promulgated a number of laws that govern the national response to emergencies in water and wastewater.