Treatability of hazardous substances in industrial wastewater: case studies for textile manufacturing and leather production sectors.

Hazardous substances used and produced by different industrial activities pose a potential risk to the environment and to human health. Different physicochemical and/or biological processes are used in industrial wastewater treatment; these methods, however, may not be effective in removing these substances. This study was carried out to comparatively evaluate the removal of hazardous substances through conventional wastewater treatment processes that are used by major industries in Turkey. A four-season monitoring study was carried out in textile manufacturing and leather production sectors, representing industrial activities in Turkey. Samples were analyzed for 45 priority substances defined by the European Union and 250 specific pollutants listed in the Turkish Regulation on Surface Water Quality. For both wastewaters, where biological treatment was performed after pretreatment, their characteristics showed that organics were almost completely removed. except for dichloromethane (44-51% removals) and dioxin and dioxin-like compounds (64-69% removals). Additionally, different removal ratios (16-97%) were obtained for metals; the poorer removal was observed for B, Ba, Ag, Sb, and Si. The remaining metals (Cu, Pb, Sb, V, Si for textile; Cr, Cu, Sb, Si for leather effluents) in the treated wastewaters were still higher than environmental quality standards (EQS) of receiving water bodies. The study revealed that existing treatment processes were not adequate for efficient hazardous substance removal and there is an urgent need to improve them. Finally, advanced treatment technologies were suggested for specific pollutants together with their unit treatment costs.

A study of inline chemical coagulation/precipitation-ceramic microfiltration and nanofiltration for reverse osmosis concentrate minimization and reuse in the textile industry.

Reverse osmosis concentrate (ROC) is one of the major drawbacks in membrane treatment technologies specifically due to the scale-forming ions. It is important to remove these ions from ROC to enhance total water recovery and reuse in the textile industry that is the largest water-consumer and polluter industry. In this work, coagulation/high pH precipitation (CP) integrated with ceramic microfiltration (CMF) was studied as a pre-treatment method followed by nanofiltration (NF) to increase the efficiency of water recovery. To prevent organic fouling, ferric chloride (FeCl3) was applied at a concentration of 3 mM, and ceramic membranes were used for the removal of non-precipitating crystals and/or suspended solids (at high pH) before the NF processes. The CP-CMF method successfully removed calcium (Ca2+), magnesium (Mg2+), silica (SiO2), and TOC up to 97, 83, 92, and 87% respectively, which resulted in higher performance of the NF process. Moreover, this method provided higher flux at lower pressure that ultimately increased overall water recovery of the NF process to achieve near-zero liquid discharge (n-ZLD). A cost-benefit estimation showed that a high-quality effluent (COD<5 mg/L; conductivity 700<µS/cm; negligible residual color) can be generated and recycled in the textile industry at an economical cost (approximately 0.97 USD/m3). Therefore, ROC minimization and water recovery can help to achieve n-ZLD using the CP-CMF/NF method.

Ceramic membrane overview and applications in textile industry: a review.

The importance of water recovery and reuse is increasing day by day. Therefore, the use of advanced technologies is applied for the treatment and recovery of textile wastewater. The fact that ceramic membranes are resistant to the challenging characteristics of textile wastewater makes the use of ceramic membranes useful. Within the scope of this review, general information about the textile industry and treatment techniques are mentioned, as well as the properties of ceramic membranes and textile wastewater treatment. In the literature review made in this study, recent studies on the production of ceramic membranes and laboratory applications have been compiled. However, it has been observed that although the real-scale studies are relatively higher in industries such as the food and petrochemical industry, it is rather limited in the textile industry.

An approach for determining the nutrient sensitive areas: a case study for Gediz River Basin, Turkey.

This study presents an approach to the determination of nutrient sensitive areas (SA) based on National Urban Wastewater Treatment Regulation harmonized under the Water Framework Directive (WFD). A three-stage approach that covers designation of potential sensitive areas (PSA) which are under the risk of eutrophication, physicochemical and biological monitoring at PSA, and application of the suitable biotic indices is used for the determination of sensitive areas. PSA are identified as a result of either available monitoring data or if this is not available according to indexing method which developed in this study based on pressure and impact analysis. The Gediz River Basin, one of the most polluted basins in Turkiye, is chosen as a pilot area. According to the results of the study, 40% of the total drainage area of the basin was designated as sensitive area.

Pilot-scale ceramic ultrafiltration/nanofiltration membrane system application for caustic recovery and reuse in textile sector.

For sustainable water management, the treatment and reuse of industrial wastewater are becoming increasingly important. There have been many studies on color removal, especially from textile wastewater. However, there are deficiencies in the literature regarding highly alkaline caustic recovery and reuse in the plant. For this reason, this study examines caustic-containing textile wastewater treatment and the reuse potential of the obtained caustic chemicals with a pilot-scale ceramic membrane system. During operations, only an ultrafiltration membrane, a nanofiltration membrane, and combined ultrafiltration + nanofiltration membranes were put to use. Chemical oxygen demand, total hardness, color, total organic carbon, sodium ion concentration, and pH tests were applied to samples, and temperature and flux were recorded throughout all operations. The obtained results showed that for ultrafiltration + nanofiltration cycles, the overall average removal efficiencies were 67, 71, 42, and 92% for total organic carbon, chemical oxygen demand, total hardness, and color respectively. For only ultrafiltration cycles, the overall average removal efficiencies were 22, 36, 25, and 63% for total organic carbon, chemical oxygen demand, total hardness, and color, respectively. Sodium values in the input wastewater were around 12 mg/L on average, and nanofiltration membrane output values changed to between 7 and 11 mg/L. Based on the sodium concentration differences between inflow and outflow samples, the permeate of ceramic membrane systems has potential for reuse in facilities.

A strategy for the implementation of water-quality-based discharge limits for the regulation of hazardous substances.

Many developing countries apply technology-based discharge standards that set quantitative limits on pollutant discharges. These standards do not inherently consider ambient constraints and, therefore, cannot guarantee to protect aquatic life from hazardous pollutants. It is a challenge for developing countries to enforce water-quality-based limits for wastewater discharges and guarantee the intended use of water. This study aims to develop a strategy that suits the needs of developing countries for a transition from technology-based discharge standards to water-quality-based discharge limits. To this end, a pilot monitoring program was carried in the Gediz River Basin in Turkey. Surface water, industrial, and urban wastewater samples were collected and analyzed for 45 priority pollutants identified by the European Union and 250 national river basin specific pollutants. The monitoring results revealed that the environmental quality standards (EQSs) were exceeded for 8 priority, and 28 specific pollutants. This finding indicated that the existing technology-based discharge standards are not satisfactory to guarantee the intended water quality, and there is a need for adopting a new strategy for the implementation of water-quality-based discharge limits in Turkey. As a widely applied approach for determining water-quality-based discharge limits, firstly, conservative mass balance with and without consideration of mixing zone was evaluated. The results indicated that this approach was not applicable due to the receiving environment concentrations being higher than the EQSs. As an alternative approach, the dilution methodology, which considers the level of dilution occurring at the immediate discharge point, was tested. The results proved that the dilution methodology is the most appropriate strategy for developing countries with relatively poor surface water quality to improve the water quality to the level where the conservative mass balance approach can be applicable.

ESR investigation on the potential use of potassium citrate as a dosimeter material.

Un-irradiated potassium citrate exhibited a weak ESR singlet at g = 2.0045 ±â€¯0.0003 with peak-to-peak line-width of ΔHpp = 0.16 mT. However, multi-resonance signals spreading over a magnetic field range of ~5 mT were observed in gamma irradiated potassium citrate. A linear function of absorbed radiation dose was found to describe well the dose-response curves of the resonance signals A, B and C in a dose range of 5-5000 Gy. Room temperature fading study showed that radiation-induced radicals in potassium citrate are highly stable but less stable when exposed to the sunlight. Three different radical species were found to describe well experimental room temperature ESR spectrum of irradiated potassium citrate. The resonance signal B can be used in measuring the accidental radiation doses and the radiation doses used in food industry, at least up to a dose of 5 kGy. Further studies were needed in order to increase the sensitivity of potassium citrate at low radiation doses.

2,4-Dichlorophenol (DCP) containing wastewater treatment using a hybrid-loop bioreactor.

Synthetic wastewater containing 2,4-dichlorophenol (DCP) was biologically treated using a hybrid-loop bioreactor system consisting of a packed column biofilm reactor (PCBR) and an aerated tank with effluent recycle. Effects of the feed DCP concentration on COD, DCP and toxicity removals were investigated. Biomass concentration in the packed column and in the aeration tank decreased with increasing feed DCP content due to toxic effects of DCP on the microorganisms. Low biomass concentrations at high DCP contents resulted in low COD, DCP and toxicity removals. Therefore, percent DCP, COD and toxicity removals decreased with increasing feed DCP content. Nearly 70% COD removal was achieved with a feed DCP content of 380 mg L(-1). The system should be operated with the feed DCP lower than 100 mg L(-1) in order to obtain DCP, COD and toxicity removals above 90%.