Pesticides in aquatic environments and their removal by adsorption methods.

Although pesticides are widely used in agriculture, industry and households, they pose a risk to human health and ecosystems. Based on target organisms, the main types of pesticides are herbicides, insecticides and fungicides, of which herbicides accounted for 46% of the total pesticide usage worldwide. The movement of pesticides into water bodies occurs through run-off, spray drift, leaching, and sub-surface drainage, all of which have negative impacts on aquatic environments and humans. We sought to define the critical factors affecting the fluxes of contaminants into receiving waters. We also aimed to specify the feasibility of using sorbents to remove pesticides from waterways. In Karun River in Iran (1.21 × 105 ng/L), pesticide concentrations are above regulatory limits. The concentration of pesticides in fish can reach 26.1 × 103 µg/kg, specifically methoxychlor herbicide in Perca fluviatilis in Lithuania. During the last years, research has focused on elimination of organic pollutants, such as pesticides, from aqueous solution. Pesticide adsorption onto low-cost materials can effectively remediate contaminated waters. In particular, nanoparticle adsorbents and carbon-based adsorbents exhibit high performance (nearly 100%) in removing pesticides from water bodies.

Comprehensive review of polycyclic aromatic hydrocarbons in water sources, their effects and treatments.

Polycyclic aromatic hydrocarbons (PAHs) are principally derived from the incomplete combustion of fossil fuels. This study investigated the occurrence of PAHs in aquatic environments around the world, their effects on the environment and humans, and methods for their removal. Polycyclic aromatic hydrocarbons have a great negative impact on the humans and environment, and can even cause cancer in humans. Use of good methods and equipment are essential to monitoring PAHs, and GC/MS and HPLC are usually used for their analysis in aqueous solutions. In aquatic environments, the PAHs concentrations range widely from 0.03 ng/L (seawater; Southeastern Japan Sea, Japan) to 8,310,000 ng/L (Domestic Wastewater Treatment Plant, Siloam, South Africa). Moreover, bioaccumulation of ∑16PAHs in fish has been reported to range from 11.2 ng/L (Cynoscion guatucupa, South Africa) to 4207.5 ng/L (Saurida undosquamis, Egypt). Several biological, physical and chemical and biological techniques have been reported to treat water contaminated by PAHs, but adsorption and combined treatment methods have shown better removal performance, with some methods removing up to 99.99% of PAHs.

Dominant Candidatus Accumulibacter phosphatis Enriched in Response to Phosphate Concentrations in EBPR Process.

Candidatus Accumulibacter phosphatis (Accumulibacter), which plays an important role in enhanced biological phosphorus removal in wastewater treatment plants, is phylogenetically classified into two major types (Types I and II). Phosphate concentrations affect the Accumulibacter community of the biomass enriched in treatment plants. Therefore, in the present study, Accumulibacter enrichments were conducted using a down-flow hanging sponge reactor under five conditions and a wide range of controlled phosphate concentrations in order to investigate how phosphate governs the community. We found that excessive phosphate levels inhibited Accumulibacter activity, that this inhibitory effect was greater for Type II. In addition, the affinity of Type II for phosphate was higher than that of Type I. Type IIA-B dominated at a phosphate concentration less than 5 mg P L-1, while Type IA was dominant at 50 and 500 mg P L-1. These patterns of enrichment may be explained by an inhibition kinetics model.

Phosphate recovery as concentrated solution from treated wastewater by a PAO-enriched biofilm reactor.

Phosphorus recovery from wastewaters and its recycling are of importance for sustaining agricultural production. During the conventional enhanced biological phosphorus removal process, phosphorus is removed by withdrawing excess sludge from wastewater. However, excess sludge disposal is costly and energy intensive. A proposed novel process for phosphorus recovery from sewage treatment will result in no excess sludge if a polyphosphate accumulating organisms (PAOs) enrichment biofilm can be applied to effluents containing phosphate. This process allows the recovery of phosphate as phosphate-concentrated solutions by controlling PAOs to absorb and release phosphate. A reactor consisting of a modified trickling filter with a synthetic substrate (5 mg P L⁻¹) was operated to form a PAO-enriched biofilm. As a result of the enrichment, the concentration of phosphate of >100 mg P L⁻¹ was successfully achieved. During this experiment, no sludge withdrawal was carried out over the duration of the operation of 255 days. To highlight the new process, the principle of enriching PAOs on biofilm and concentrating phosphate from treated sewage is explained, and a discussion on phosphate recovery performance is given.