Maha Halalsheh

Grey water characteristics and treatment options for rural areas in Jordan

Low water consumption in rural areas in Jordan had resulted in the production of concentrated grey water. Average COD, BOD and TSS values were 2568mg/l, 1056mg/l and 845mg/l, respectively. The average grey water generation was measured to be 14L/c.d. Three different treatment options were selected based on certain criterions, and discussed in this article. The examined treatment systems are septic tank followed by intermittent sand filter; septic tank followed by wetlands; and UASB-hybrid reactor. Advantages and disadvantages of each system are presented. It was concluded that UASB-hybrid reactor would be the most suitable treatment option in terms of compactness and simplicity in operation. The volume of UASB-hybrid reactor was calculated to be 0.268m(3) with a surface area of 0.138m(2) for each house having 10 inhabitants on average. Produced effluent is expected to meet Jordanian standards set for reclaimed water reuse in irrigating fruit trees.

Effect of increasing the surface area of primary sludge on anaerobic digestion at low temperature.

Two sets of reactors were operated at 15°C and at sludge retention times (SRTs) of 65 days and 30 days, respectively. Each set was operated at six different mixing velocities. Shear forces provided by mixing affected particle size distribution and resulted in different sludge surface areas. The aim was to investigate the effect of increasing primary sludge surface area on anaerobic digestion at low temperature. The maximum surface areas at the applied mixing velocities were 5926 cm2/cm3of sludge and 4672 cm2/cm3 of sludge at SRTs of 65 days and 30 days, respectively. The corresponding calculated methanogenesis were 49% and 15% at SRTs of 65 days and 30 days, respectively. Maximum total solids (TS) reductions were 26% and 11% at 65 days and 30 days SRTs, respectively. Lipase activity increased with increasing SRT and sludge surface area. Results clearly showed that increasing sludge surface area improved sludge digestion at 15°C.

Anaerobic treatment of strong sewage by a two stage system of AF and UASB reactors

An anaerobic treatment system that consists of an Anaerobic Filter (AF) and an Upflow Anaerobic Sludge Blanket (UASB) in series was built and operated to investigate its performance in treating strong domestic wastewater with high suspended solids fraction under Jordans ambient temperatures of 25 degrees C for summer and 18 degrees C for winter. The system was operated from September 2003 until early April 2004. The system was operated at a Hydraulic Retention Time (HRT) of 4 hours for the first stage AF and 8 hours for the second stage UASB. Average COD(t) and COD(ss) removal efficiencies of the AF/UASB were 58% and 81% respectively for the operation period. The results showed that the first stage AF was effective in removing suspended solids. In addition, hydrolysis, acidification and methanogenesis took place in the first stage AF which was advantageous to the second stage UASB. It was concluded that the AF/UASB system is effective in treating strong domestic wastewater with high suspended solids content under Jordans ambient temperatures.

Anaerobic wastewater treatment of concentrated sewage using a two-stage upflow anaerobic sludge blanket- anaerobic filter system

A two-stage pilot-scale upflow anaerobic sludge blanket – anaerobic filter (UASB-AF) reactors system treating concentrated domestic sewage was operated at 23°C and at hydraulic retention times (HRT) of 15 and 4 h, respectively. Excess sludge from the downstream AF stage was returned to the upstream UASB reactor. The aim was to obtain higher sludge retention time (SRT) in the UASB reactor for better methanization of suspended COD. The UASB-AF system removed 55% and 65% of the total COD (CODtot) and suspended COD (CODss), respectively. The calculated SRT in the UASB reactor ranged from 20–35 days. The AF reactor removed the washed out sludge from the first stage reactor with average CODss removal efficiency of 55%. The volatile fatty acids concentration in the effluent of the AF was 39 mg COD/L compared with 78 mg COD/L measured for the influent. The slightly higher CODtot removal efficiency obtained in this study compared with a single stage UASB reactor was achieved at 17% reduction in the total volume.

Fate of Pathogens In Tomato Plants and Soil Irrigated With Secondary Treated Wastewater

Pathogenic indicators, namely total coliform, E. coli and Enterococcus were measured on harvested tomato fruits and leaves and in soil irrigated with fresh water, effluent of extended aeration wastewater treatment plant and effluent of upflow anaerobic sludge blanket-rotating biological contactors integrated pilot treatment system. Plantation was taking place in a greenhouse during summer in Jordan. A drip irrigation system was applied in which laterals were covered with mulch to minimize contact between irrigation water and plants. Results showed that total coliform and Enterococcus counts in all tomato fruit samples (except one) and E. coli count in all harvested tomato fruit samples were less than 1 MPN/g dry plant. Although secondary treated wastewater had indicator pathogenic counts of 2 to 5 log units, a considerable reduction was noticed in the collected soil samples after 10 days of the last irrigation. All soil samples contained less than 1 MPN/g dry soil of E. coli, while total coliform counts ranged from less than 1 to 19.23 MPN/g dry soil. The results suggest that disinfection of the reclaimed wastewater may not be necessary with respect to the measured indicator pathogens when proper agricultural practices are applied.

Anaerobic filter for polishing effluent of UASB reactor treating strong sewage at 23°C

Anaerobic filter (AF) was used for polishing effluent of UASB reactor treating strong sewage at an average water temperature of 23 degrees C. The UASB-AF system was operated with sludge discharge taking place only from the AF reactor. It was hypothesized that better removal of suspended COD (COD(ss)) fraction from the system can be achieved by increasing sludge discharge frequency from the AF reactor. For this purpose, sludge discharge frequencies of once, twice and thrice per day from the AF reactor were investigated. Results showed that average total COD (COD(tot)) removal efficiency of the system increased from 62% when sludge was discharged once per day from the AF reactor up to 67% when sludge was discharged twice and thrice per day. However, the increase in COD(tot) removal was not due to increased removal of COD(ss) fraction; but mainly due to development of an active biomass on the filter media, which increased removal efficiency of soluble COD fraction. The AF reactor had also an evidence of pathogens reduction. The AF reactor achieved 1-2 log reduction in Fecal Coliform counts.

Improving solids retention in upflow anaerobic sludge blanket reactors at low temperatures using lamella settlers

Lamella settlers were used to increase sludge concentration in pilot scale UASB reactors treating concentrated sewage at low temperature. The aim was to increase sludge retention time (SRT) and achieve better digestion in UASB reactors without the need for increasing the hydraulic retention time (HRT). Two modified UASB reactors were used for this purpose. In the first reactor, lamella settlers were installed in the settling zone of the UASB reactor and the reactor was named UASB-ESR1. In the second reactor, lamella settlers were installed underneath the gas liquid separator (GLS) and the reactor was named UASB-ESR2. The sludge concentration, sludge profile, and system performance of each reactor were monitored. The obtained sludge concentrations were 50 and 53 g TS/l for UASB-ESR1 and UASB-ESR2, respectively. The measured concentrations were almost double the concentrations reported for conventional UASB reactors ranging 16–26 g TS/l. The calculated SRT in the modified UASB reactors was 103 days in both reactors. The average total COD (COD tot ) and suspended COD (COD ss ) removal efficiencies were 38% and 60%, respectively for the UASB-ESR1. The average COD tot and COD ss removal efficiencies for the UASB-ESR2 were 41% and 62%, respectively. The modified reactors were considered at the startup period and the performances of the modified systems are expected to significantly improve when arriving at steady state conditions.