R. Etchepare

Health risk assessment of organic micropollutants in greywater for potable reuse.

In light of the increasing interest in development of sustainable potable reuse systems, additional research is needed to elucidate the risks of producing drinking water from new raw water sources. This article investigates the presence and potential health risks of organic micropollutants in greywater, a potential new source for potable water production introduced in this work. An extensive literature survey reveals that almost 280 organic micropollutants have been detected in greywater. A three-tiered approach is applied for the preliminary health risk assessment of these chemicals. Benchmark values are derived from established drinking water standards for compounds grouped in Tier 1, from literature toxicological data for compounds in Tier 2, and from a Threshold of Toxicological Concern approach for compounds in Tier 3. A risk quotient is estimated by comparing the maximum concentration levels reported in greywater to the benchmark values. The results show that for the majority of compounds, risk quotient values were below 0.2, which suggests they would not pose appreciable concern to human health over a lifetime exposure to potable water. Fourteen compounds were identified with risk quotients above 0.2 which may warrant further investigation if greywater is used as a source for potable reuse. The present findings are helpful in prioritizing upcoming greywater quality monitoring and defining the goals of multiple barriers treatment in future water reclamation plants for potable water production.

Car wash wastewater treatment and water reuse – a case study

Recent features of a car wash wastewater reclamation system and results from a full-scale car wash wastewater treatment and recycling process are reported. This upcoming technology comprises a new flocculation-column flotation process, sand filtration, and a final chlorination. A water usage and savings audit (22 weeks) showed that almost 70% reclamation was possible, and fewer than 40 L of fresh water per wash were needed. Wastewater and reclaimed water were characterized by monitoring chemical, physicochemical and biological parameters. Results were discussed in terms of aesthetic quality (water clarification and odour), health (pathological) and chemical (corrosion and scaling) risks. A microbiological risk model was applied and the Escherichia coli proposed criterion for car wash reclaimed water is 200 CFU 100 mL(-1). It is believed that the discussions on car wash wastewater reclamation criteria may assist institutions to create laws in Brazil and elsewhere.

Application of flocculation–flotation followed by ozonation in vehicle wash wastewater treatment/disinfection and water reclamation

AbstractThis article provides the results of flocculation–flotation followed by sand filtration and ozonation (FFO), applied for the treatment of car wash wastewater in a water reclamation system in Brazil. The assessment of the efficiency of the process in enhancing reclaimed water quality, especially aesthetic, microbiological, and chemical issues is reported. The FFO process provided disinfected (Escherichia coli < 1.8 CFU 100 mL−1) and clarified water (10 NTU), minor foaming (residual surfactants = 1.30 mg L−1MBAS), and no odor-related problems from reclaimed water. Comparative studies were carried out at bench scale; ozone (AOP) and chlorine were applied separately as oxidation procedures and a mass balance was assessed as a function of the number of water cycles. Results revealed that besides higher oxidation of organics and water clarification, both conductivity and dissolved solids concentrations for the ozone-treated water were lower than those obtained with the chlorinated water. A cost–benefit ...

Raw water clarification by flotation with microbubbles and nanobubbles generated with a multiphase pump

Raw water clarification by flotation was studied by injecting air into a centrifugal multiphase pump to generate microbubbles (MBs) and nanobubbles (NBs). Measurements of gas dispersion parameters were performed and optimal conditions were obtained using a pump pressure of 4 bar. Values showed a bubble Sauter diameter of 75 μm, an air holdup of 1.2%, a bubble surface area flux of 34 s-1 and an NB concentration of 1 × 108 NBs mL-1 (measuring 220 nm). Then, a study compared flotation with bubbles formed with the multiphase pump (F-MP) to lamellar settling at the clarification stage of a water treatment plant (WTP), in Brazil. The F-MP showed a higher separation efficiency at high hydraulic loads (9-15 m h-1), even without the use of a polymer, reaching 2 NTU (10-25 NTU raw water feed), which was much lower than the technical goal of the WTP (5 NTU). The results and the technical aspects are discussed, and it is concluded that the employment of MBs and NBs with pumps widens new research lines and applications in modern flotation.

Separation of emulsified crude oil in saline water by flotation with micro- and nanobubbles generated by a multiphase pump

The flocculation-column flotation with hydraulic loading (HL, >10 m h-1) was studied for the treatment of oil-in-water emulsions containing 70-400 mg L-1 (turbidity = 70-226 NTU) of oil and salinity (30 and 100 g L-1). A polyacrylamide (Dismulgan, 20 mg L-1) flocculated the oil droplets, using two floc generator reactors, with rapid and slow mixing stages (head loss = 0.9 to 3.5 bar). Flotation was conducted in two cells (1.5 and 2.5 m) with microbubbles (MBs, 5-80 μm) and nanobubbles (NBs, 50-300 nm diameter, concentration of 108 NBs mL-1). Bubbles were formed using a centrifugal multiphase pump, with optimized parameters and a needle valve. The results showed higher efficiency with the taller column reducing the residual oil content to 4 mg L-1 and turbidity to 7 NTU. At high HL (27.5 m h-1), the residual oil concentrations were below the standard emission (29 mg L-1), reaching 18 mg L-1. The best results were obtained with high concentration of NBs (apart from the bigger bubbles). Mechanisms involved appear to be attachment and entrapment of the NBs onto and inside the flocs. Thus, the aggregates were readily captured, by bigger bubbles (mostly MBs) aiding shear withstanding. Advantages are the small footprint of the cells, low residence time and high processing rate.