title: Effect of hydraulic retention time on the performance of down-flow hanging sponge system treating grey wastewater.
abstract: Grey wastewater (GW) treatment via down-flow hanging sponge (DHS) system was the subject of the study. The reactor was operated at different hydraulic retention times (HRTs) of 11.7, 5.8 and 2.9 h, corresponding to organic loading rates (OLRs) of 1.9, 3.6 and 6.8 kgCOD/m3 day, respectively. The results obtained revealed that decreasing the HRT from 11.7 to 2.9 h negatively affected on the performance of the DHS system. COD(total), COD(soluble), COD(particulate) and detergent removal efficiency were reduced from 96 ± 2.4 to 90 ± 2.3%, from 83 ± 10 to 69 ± 8%, from 98 ± 2 to 94 ± 3% and from 96 ± 12 to 88 ± 6.9%, respectively. However, the removal efficiency of the distinguished COD fractions and detergent remained unaffected when decreasing the HRT from 11.7 to 5.8 h. The DHS system provided a removal efficiency of 95 ± 1% for COD(total), 79 ± 8% for COD(soluble), 98 ± 2 for COD(particulate) and 94.7% for detergent at an HRT of 5.8 h. Based on these results, it is recommended to operate such a system at an HRT of 5.8 h and OLR not exceeding 3.6 kgCOD/m3 day for producing an effluent quality complying for reuse in unrestricted irrigation purposes. The removal of TKj-N and nitrification efficiency in the DHS system was significantly affected by increasing the OLR from 1.9 to 3.6 kgCOD/m3 day and from 3.6 to 6.8 kgCOD/m3 day. At an OLR of 1.9 kgCOD/m3 day, the DHS system removed 80 ± 12% of TKj-N and 91 ± 22% of ammonia which is significantly higher than that at an OLR of 3.6 (58.5 ± 13%) and 6.8 kgCOD/m3 day (26.8 ± 16%). Similar results were recorded for the removal of total coliform (TC), viz., the efficiencies dropped for TC from 99.8 ± 0.2 to 99.4 ± 0.8% and from 99.4 ± 0.8 to 90.0 ± 7.6%, respectively. DHS profile results showed that the major part of COD was removed in the upper portion of the system while the nitrification process was taken place in the lower part of the DHS system at OLR of 1.9 kgCOD/m3 day and HRT of 11.7 h.
authors.affiliation: School of Energy Resources and Environmental Engineering, Egypt-Japan University of Science and Technology (E-Just), P.O. Box 179, New Borg El Arab City, Alexandria, 21934, Egypt. Tawfik8@hotmail.com.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Tawfik
authors.forename: Rifaat Abdel
authors.initials: RA
authors.lastname: Wahab
authors.forename: Azza
authors.initials: A
authors.lastname: Al-Asmer
authors.forename: Fatma
authors.initials: F
authors.lastname: Matary
mesh_terms: D003902:Detergents / Q000032:analysis; D003906:Developing Countries; D004755:Enterobacteriaceae / Q000302:isolation & purification*; D004867:Equipment Design; D006801:Humans; D008855:Microscopy, Electron, Scanning; D058465:Nitrification; D013696:Temperature; D013997:Time Factors; D014865:Waste Disposal, Fluid / Q000295:instrumentation / Q000379:methods*; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000302:isolation & purification; D018508:Water Purification / Q000295:instrumentation / Q000379:methods
chemical_list: D003902:Detergents; D014874:Water Pollutants, Chemical