No abstract

No abstract

The main theme of the study was a comparative study of domestic wastewater treatment using conventional and baffled septic tanks. The septic tanks were fed continuously with domestic wastewater at three different hydraulic retention times (HRTs). The HRTs chosen were 24, 48 and 72 h with corresponding organic loads of 0.321, 0.436 and 0.885 kg chemical oxygen demand (COD) per m3 per day, respectively. The performance of the septic tanks at the three HRTs gave satisfactory results. For the conventional septic tank, COD removal was 53.4%, 56% and 65.3%, at an HRT of 24, 48 and 72 h, respectively, with residual COD of 412, 380 and 334mg/l, respectively. At HRTs of 72, 48 and 24 h, the following percentages removals were realized for: biochemical oxygen demand (BOD), 68.4%, 57, 53.5%; total suspended solid (TSS), 65.3%, 58.3, 55%; phosphorus, 29.3%, 26.9, 25.6%; total Kjeldahl nitrogen 26.8%, 20.8, 17.7%, respectively. On the contrary, ammonia concentrations increased by 7.1%, 5.2 and 4.2% under the same conditions. Consequently, the results showed that the removal of fecal coliform at all HRTs was less than one log. The two baffled septic tanks exhibited superior results at HRTs of 72, 48 and 24 h. Comparing the treated domestic wastewater quality produced by the two types of septic tanks in terms of physico-chemical and biological characteristics, better results were obtained using the two baffles type.

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.

No abstract