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The treatment and reuse of domestic wastewater using an anaerobic baffled reactor (ABR) followed by a duckweed pond (DWP) were the main theme of the present study. The ABR was fed continuously with domestic wastewater at four HRTs ranging from 8 to 24 h and corresponds to organic loading rates ranging from 0.67 to 2.1 kg COD/m 3 /day. The ABR effluent was fed to a DWP operating at 10 and 15 days. The performance of the ABR at the four HRTs gave satisfactory results. Chemical oxygen demand (COD) removal was between 68 and 82%. Fecal coliform removal was between 1 to 2 logs. The 12-and 18-h hydraulic retention times (HRTs) gave close results, as indication of the possible selection of the 12-h HRT as the optimum operation for the ABR based on economic advantage. The ABR compartmentalized structure gave results higher than those produced by the onestage digester and similar to those produced by the twophase anaerobic digestion process. Duckweed ponds as post-treatment operated at 10 days and 15 days gave the best results at 15-day HRT, where it was possible to remove 73.4% of nitrogen and 65% of phosphorus and produce protein-rich dry duckweed of 105 kg/ha/day on average. The removal of fecal coliform (FC) in duckweed ponds was 3-4 logs. The final treated domestic sewage characteristics proved its compliance with the Egyptian standards for reuse in restricted irrigation.

Treatment of chemical industrial wastewater from building and construction chemicals factory and plastic shoes manufacturing factory was investigated. The two factories discharge their wastewater into the public sewerage network. The results showed the wastewater discharged from the building and construction chemicals factory was highly contaminated with organic compounds. The average values of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were 2912 and 150 mgO 2 /l. Phenol concentration up to 0.3 mg/l was detected. Chemical treatment using lime aided with ferric chloride proved to be effective and produced an effluent characteristics in compliance with Egyptian permissible limits. With respect to the other factory, industrial wastewater was mixed with domestic wastewater in order to lower the organic load. The COD, BOD values after mixing reached 5239 and 2615 mgO 2 /l. The average concentration of phenol was 0.5 mg/l. Biological treatment using activated sludge or rotating biological contactor (RBC) proved to be an effective treatment system in terms of producing an effluent characteristic within the permissible limits set by the law. Therefore, the characteristics of chemical industrial wastewater determine which treatment system to utilize. Based on laboratory results engineering design of each treatment system was developed and cost estimate prepared.

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This study aimed to investigate, from a techno-economic point of view, cattle slaughterhouse wastewater (CSWW) treatment via the electrocoagulation (EC) technique. A novel lab-scale EC unit with a 3 L volume was manufactured and tested. The EC unit contains nine identical cylindrical shape electrodes from aluminum material in connection with a controllable DC power supply. Investigation of optimum operating parameters in terms of pH, current density (CD), contact time, and electrolyte concentration was carried out in batch mode and then applied to continuous mode. At each batch, a cost analysis was calculated in terms of the consumption of electrode material and electrical power. The optimum operating conditions at which the best removal efficiency was achieved were pH 7, contact time 75 min, total dissolved solids of 3000 mg L−1, and CD of 4 mA cm−2. After application of these conditions on continuous flow mode, the removal efficiency of chemical oxygen demand, color, turbidity, biological oxygen demand, and oil, grease were 95, 99, 99, 97 and 95%, respectively. The total electrode consumption and electrical consumptions were 0.6 kg m−3 and 0.87 kWh m−3 with an operational cost of about $1.5 m−3. This proved that EC is a techno-economically effective treatment method than other conventional treatment methods for high-rate removal of pollutants from CSWW.