Treatment of domestic sewage at low temperature in a two-anaerobic step system followed by a trickling filter.
The treatment of domestic sewage at low temperature was studied in a two-anaerobic-step system followed by an aerobic step, consisting of an anaerobic filter (AF) + an anaerobic hybrid (AH) + polyurethane-foam trickling filter (PTF). The AF+AH system was operated at a hydraulic retention time (HRT) of 3+6 h at a controlled temperature of 13 degrees C, while the PTF was operated without wastewater recirculation at different hydraulic loading rates (HLR) of 41, 15.4 and 2.6 m3/m2/d at ambient temperature (ca. 15-18 degrees C). The AF reactor removed the major part of the total and suspended COD, viz. 46 and 58% respectively. The AH reactor with granular sludge was efficient in the removal and conversion of the anaerobically biodegradable COD. The AF+AH system removed 63% of total COD and converted 46% of the influent total COD to methane. At a HLR of 41 m3/m2/d, the COD removal was limited in the PTF, while at HLR of 15.4 and 2.6 m3/m2/d, a high total COD removal of 54-57% was achieved without a significant difference between the two HLRs. The PTF was mainly efficient in the removal of particles (suspended and colloidal COD removal were 75-90% and 75-83% respectively), which were not removed in the anaerobic two-step. The overall total COD removal in the AF+AH+PTF system was 85%. Decreasing the HLR from 15.4 to 2.6 m3/m2/d, only increased the nitrification rate efficiency in the PTF from 22% to 60%. Also, at HLR of 15.4 and 2.6 m3/m2/d, PTF showed a similar removal for E. coli by about 2 log. Therefore, the effluent of AF+AH+PTF system can be utilised for restricted irrigation in order to close water and nutrients cycles. Moreover, such a system represents a high-load and a low-cost technology, which is a suitable solution for developing countries.
Elmitwalli
T A
TA
Department of Civil Engineering, Benha High Institute of Technology, P.O. Box 13512, Benha El-Gedida, Benha, Egypt. t_elmitwalli@hotmail.com
van Lier
J
J
Zeeman
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Lettinga
G
G
D001421:Bacteria, Anaerobic; D001673:Biodegradation, Environmental; D005374:Filtration; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism; D012722:Sewage / Q000737:chemistry*; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods*; D014872:Water Movements; D018508:Water Purification / Q000379:methods*
D012722:Sewage; D010100:Oxygen