Reclamation of Cobalt and Copper from Single- and Co-contaminated Wastewater via Carbonate and Hydroxide Precipitation

Wastewater containing cobalt and copper comprised of plating wash water, plant wash water, and equipment cooling and wash water is generated in the electroplating industry. These metals can be detrimental to humans, animals, plants, and the environment. Thus, it is necessary to treat electroplating wastewater to remove these toxic metals. Carbonate and hydroxide precipitation were utilized for the removal of Co(II) and Cu(II) from synthetic electroplating wastewater by jar tests in this work. The effects of solution pH, precipitant-to-metal ratio, and type of precipitant on the precipitation efficiency of cobalt and copper from the single- and co-contaminated systems were investigated. Carbonate precipitation achieved higher removal efficiency for both target metals in the single- and co-contaminated wastewater streams. Furthermore, it can operate at relatively low pH range of about 7.0-8.0. Cobalt in both pollutant systems was almost completely removed at pH 10.0 using both precipitant systems. Copper was found to be easily removed which was possibly brought about by precipitation-adsorption mechanism. The extent of the co-removal of cobalt with copper is significantly pH dependent. The effect of precipitant-to-metal ratio for cobalt and copper treatment varied in single- and co-contaminated streams. Carbonate precipitation led to lower sludge density than that of hydroxide precipitation.

Extended-Spectrum Beta-Lactamase Producing-Escherichia coli Isolated From Irrigation Waters and Produce in Ecuador

In cities across the globe, the majority of wastewater – that includes drug resistant and pathogenic bacteria among other contaminants – is released into streams untreated. This water is often subsequently used for irrigation of pastures and produce. This use of wastewater-contaminated streams allows antibiotic-resistant bacteria to potentially cycle back to humans through agricultural products. In this study, we investigated the prevalence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolated from produce and irrigation water across 17 provinces of Ecuador. A total of 117 vegetable samples, 119 fruit samples, and 38 irrigation water samples were analyzed. Results showed that 11% of the samples were positive for E. coli including 11 irrigation water samples (29%), and samples of 13 vegetables (11%), and 11 fruits (9%). Among the 165 E. coli isolates cultured, 96 (58%) had the ESBL phenotype, and 58% of ESBL producing E. coli came from irrigation water samples, 11% from vegetables, and 30% from fruits. The blaCTX–M–55, blaCTX–M 65, and blaCTX–M 15 genes were the most frequently found gene associated with the ESBL phenotype and coincided with the blaCTX–M alleles associated with human infections in Ecuador. Three isolates had the mcr-1 gene which is responsible for colistin resistance. This report provides evidence of the potential role of irrigation water in the growing antimicrobial resistance crisis in Ecuador.

Microbiological and chemical evaluation of acid mine drainage from mining sites in Southwestern, Nigeria

Microbial content of acid mine drainage effluents contaminated streams from some geographical areas was evaluated. Water was obtained from acid mine drainage sites in Ekiti and Osun state where twelve (12) samples were obtained from different locations. Culture plating method was used to analyze the samples for bacteria, and Atomic Absorption Spectrophotometer (AAS) was used to determine heavy metals such as Cd, Co, Pb, Cr, Zn, Cu and Mn. The results of biochemical and morphological characterization of the isolates revealed three probable bacterial from the samples which are Bacillus subtilis, Pseudomonas spp. and Staphylococcus aureus; B. subtilis being the bacteria with the highest percentage frequency of occurrence. Heavy metals analysis of the mine drains shows that the concentration of Cd, Co, Pb, Cr and Zn exceeded permissible limit set by WHO except Cu and Mn. The results of this study established the presence of bacterial and heavy metals in acid mine drainage sites, which is an indication that the acid mine effluents are contaminated. It is therefore essential for proper dissemination of information concerning the dangers these microbes and heavy metals could pose to human.

SEM-EDX Analysis of Heavy Metals in Anal Papillae of Hydropsyche Angustipennis Larvae (Trichoptera, Insecta) as a Support for Water Quality Assessment

Anal papillae of caddisflies are peripheral organs responsible for osmoregulation and detoxification. Investigation of morphological abnormalities in the anal papillae of Hydropsyche angustipennis enriched with using SEM-EDX analysis (scanning electron microscopy-energy dispersive X-ray analysis), was used to assess heavy metal pollution levels in urban streams receiving surface runoff. Heavy metal ions not previously detected in water and tissue samples were detected using SEM-EDX method. Morphological irregularities were most frequently observed in larvae from the most contaminated streams. Heavy metals were almost 10 times more concentrated in darkened papillae than in pale, normal-shaped papillae. The present study confirms that SEM-EDX microscopy is an effective method as a support of standard heavy metal bioassays, especially if there is a necessity to detect trace elements in very low concentrations or incidental appearance of some ions in the water.

Difference of ecological half-life and transfer coefficient in aquatic invertebrates between high and low radiocesium contaminated streams

The Fukushima accident emitted radioactive substances into the environment, contaminating litter, algae, sand substrate, aquatic invertebrates, and fish in freshwater streams. Because these substances have substantial effects on stream ecology over many years, it is necessary to clarify the diffusion and decay mechanisms of radiocesium. The transfer coefficient differed among aquatic invertebrate groups, likely due to the differences in habitat. The ecological half-life of cesium was longer where the air dose rate was lower. The transfer coefficient was also higher in areas with lower air dose rate. The radiocesium concentration in algae was inversely related to stream current velocity in the radiocesium-contaminated area. However, this relationship was not observed in the lower air dose rate area: the radiocesium concentration in algae in the rapid-velocity areas tended to be higher than that in the slow-velocity areas. This reverse trend would lead to a longer period of freshwater contamination. The radiocesium concentration would continue to decrease in highly contaminated areas, but it would be difficult to reduce the radiocesium concentration in less-contaminated areas because different contamination mechanisms are at work. Controlling the water flow is key to regulating radiocesium concentration in freshwater ecosystems.

Are fungal strains from salinized streams adapted to salt-rich conditions?

Anthropogenic salinization of freshwater is a global problem with largely unknown consequences for stream functions. We compared the effects of salt addition (6 g l −1 NaCl) in microcosms on leaf mass loss and microbial parameters in single- and multispecies assemblages of fungal strains ( Heliscus lugdunensis , HELU; Tetracladium marchalianum , TEMA; Flagellospora curta , FLCU) isolated from a reference (R) or salinized (S) stream. Fungal growth and interactions were also assessed. Salinization inhibited leaf decomposition and fungal biomass, but no differences were observed between species, strains or species combinations. Sporulation rates in monocultures were not affected by added salt, but differed among species (FLCU > HELU > TEMA), with S strains releasing more conidia. Fungal assemblages did not differ significantly in total conidia production (either between strains or medium salt concentration). HELU was the dominant species, which also had highest growth and most pronounced antagonistic behaviour. Fungal species, irrespective of origin, largely maintained their function in salinized streams. Strains from salt-contaminated streams did not trade-off conidial production for vegetative growth at high salt levels. The expected reduction of fungal diversity and potential changes in nutritional litter quality owing to salinization may impact leaf incorporation into secondary production in streams. This article is part of the theme issue ‘Salt in freshwaters: causes, ecological consequences and future prospects’.