This study aimed to evaluate the efficiency of a novel pilot-scale passively aerated biological filter (PABF) as a low energy consumption system for the treatment of municipal wastewater. It consists of four similar compartments, each containing 40% of a non-woven polyester fabric as a bio-bed. The PABF was fed with primary treated wastewater under a hydraulic retention time (HRT) of 3.5 hr and a hydraulic loading rate of 5.5 m²/m³/d. The effect of media depth, HRT, dissolved oxygen (DO) and surface area of the media on the removal efficiency of pollutants was investigated. Results indicated that increasing media depth along the axis of the reactor and consequently increasing the HRT and DO resulted in great removal of different pollutants. A significant increase in the DO levels in the final effluent up to 6.7 mg/l resulted in good nitrification processes. Statistical analysis using SPSS showed that the reactor performance has significant removal efficiency (p < .05) for all pollutants. Overall results indicated that PABF is a viable ecological engineering approach that can be optimized and applied to improve water quality with minimal consumption of energy and low sludge production compared with conventional activated sludge and trickling filter systems.

The aim of this study was to evaluate the performance of two pilot horizontal flow constructed wetlands (HFCWs) with and without vegetation. Three types of plants namely Canna, Phragmites australis and Cyprus papyrus were used. The surface area of each plant was 654 m2. The flow rate was 20 m3 d−1 and the organic loading rate range was 1.7–3.4 kg BOD d−1 with a detention time of 11 days. The results obtained showed that planted HFCW produced high quality effluent in terms of reduction of chemical oxygen demand (COD; 88%), biochemical oxygen demand (BOD; 91%) and total suspended solids (TSS; 92%) as well as nutrient removal. In addition, 4 logs of total coliform were removed from the planted unit compared with only 3 logs in the unplanted one. The phosphate uptake by the plants reached 29, 30.91 and 38.9 g P m−2 for Canna, Phragmites and Cyprus, respectively, with 60% removal rate in the treated effluent. The nitrogen uptake by the same plants reached 63.1, 49.46 and 82.33 g N m−2. Although, the unplanted unit proved to be efficient in the removal of COD, BOD and TSS, it lacks efficiency in pathogen and nutrient removal. The reclaimed wastewater, after disinfection, could be reused for non-restricted irrigation purposes.

The process of retting flax produces a huge amount of wastewater which is characterized with bad unpleasant smell and high concentration of organic materials. Treatment of such waste had always been difficult because of the presence of refractory organic pollutants such as lignin. In this study, treatment of retting wastewater was carried out using combined system of Fenton oxidation process followed by adsorption on granular activated carbon (GAC). The effects of operating condition on Fenton oxidation process such as hydrogen peroxide and iron concentration were investigated. In addition, kinetic study of the adsorption process was elaborated. The obtained results indicated that degradation of organic matters follows a pseudo-first order reaction with regression coefficient of 0.98. The kinetic model suggested that the rate of reaction was highly affected by the concentration of hydrogen peroxide. Moreover, the results indicated that the treatment module was very efficient in removing the organic and inorganic pollutants. The average percentage removal of chemical oxygen demand (COD), total suspended solid (TSS), oil, and grease was 98.60%, 86.60%, and 94.22% with residual values of 44, 20, and 5mg/L, respectively. The treated effluent was complying with the National Regulatory Standards for wastewater discharge into surface water or reuse in the retting process