Results - Technological Demonstration Centers (TDCs)

Description of the Training and Demonstration centre (TDC) of Institut Agronomique et Vétérinaire Hassan II (IAV), Rabat, Morocco

The TDC is constructed in the area harboring the existing wastewater treatment plant of the IAV Campus. The later was constructed in late 1996 to be used as a research and teaching support and has therefore many associated components and facilities. But the principal biological techniques tested are: Two-Step Upflow Anaerobic Reactor (TSUAR), a high-rate algae pond followed by a maturation ponds and a multi-stage constructed wetland.

The funds to construct the TDC are allowed by the European Commsion (UE), within the frame work of MEDA Water project (Zer0-M), by the Canadian "Programme Universitaire de Coopération et de Développement" shared with the University of Guelph and of course by the IAV. The European money is mainly used to widen the TDC capabilities to include some of the closing loop and low cost and environmentally friendly techniques. The TDC is used as a support to the numerous training sessions also funded by Zer0-M project. The following description focuses on greywater treatment and recycling and on the hybrid-multistage constructed wetland.

TDC layout

1. Setup of the GW recycling system: The Club of the “Association Culturelle et Sportive de l'Agriculture” (ACSA) and the Campus of IAV Hassan II in Rabat lie next to each other. Around 8 m3/d of greywater (GW) from the showers of the Gym room users are segregated from toilet effluent. Collected GW is pumped out to the wastewater treatment facility located inside the IAV Campus and recycled for flushing in the toilets of the Department of Rural Engineering.

1.1. Greywater treatment (see photos): Greywater is treated in three different units inside the campus namely: Constructed wetland (CW) followed by a Vertical-flow sand filter followed by UV disinfection, Submerged Membrane Sequencing Batch Reactor (SM-SBR) and SBR without membrane including UV disinfection. The last two are compact and mechanically aerated units.

1.1.1. The Constructed wetland/sand filter/UV disinfection: The CW is constructed in reinforced concrete and has the following characteristics: length 2.25 m, width 2.0 m, depth 0.8 m, cross sectional area 1.6 m2 and bottom slope 2%. The bed filling material consists of limestone aggregates with an effective diameter of 5.5 mm. The uniformity coefficient (UC; d60/d10) is 1.60, the porosity 47%, and the clean Darcy's hydraulic conductivity, K, is 60 10-3 m/s. The bed is planted with reed; Phragmites sp. The hydraulic loading rate is 1.8 m/d with an organic load of 210 g COD/(m²*d). The vertical multilayer sand filter is also made in reinforced concrete and has the same dimensions as the CW. Five sand layers of 0.14 m thick each with particle sizes going from 0.55 to 6 mm are used. The measured clean Darcy's hydraulic conductivity, K, of the unit is 25.10-3 m/s. The effluent of this unit is then disinfected in an UVTspa Teflon system (Iritech Finmeccanica, Italy). GW is pumped upward in a Teflon pipe placed in an aluminum box with dimensions of 0.20 m x 1.70 m x 0.20 m. The Teflon pipe is surrounded by four 0.90 m long low-pressure mercury tubes of 30 Watts each emitting at 253.7 nm and placed at a distance of 0.03 m from the Teflon tube. The contact time is adjusted to 6.35 s leading to a dose of 400 mJcm-2.

The MBR technology combines activated sludge process, for the removal of biodegradable pollutants, and membrane filtration for solid/liquid separation. The equipment used is from Busse, Germany, type MF-GW-HKA 4 (one reservoir). The membrane is a 5 m² "frame and plates" made of polyelectrolyte complex (Kubota, Japan) with a nominal pore size of 0.4 µm. The operating conditions were as follows: cycle duration 3 h (8 cycles/d); contact time 25 min (treatment aeration) then intermittent aeration (10 min every one hour); flow 675 L/d and HRT 19.5 h. After some time, the cycle was reduced to 2h, (12 cycles/d) to treat 980 L/d at HRT of 13.5 h. The purchase of the large unit was preceded by bench-pilot experiments (see (Merz et al., 2007). The COD load was decreased from 0.16 to 0.14 g COD/ (g VSS*d) when the cycle was reduced from 3 to 2 hours.

The SBR is an activated sludge unit in which the biomass grows inside small floating foam cubes. The unit used is an Aquacycle 900 from Pontos, Germany. It includes 3 reservoirs, two for the treatment and the third for storing the UV-disinfected effluent. Operating conditions were as follows: Cycle duration 3 h, i.e. 8 cycles/d; (3min aeration and 5 min rest) followed by 20 min settling period corresponding to 850 L/d and 16.5 h as HRT. The settled material was pumped out every 4 days. The operating conditions were later changed to a cycle of 2 hours i.e., 12 cycles/d (3 min aeration and 5 min rest) followed by 20 min settling period corresponding to 1100 L/d and 13 h as HRT. The COD load was 0.2 g COD/ (g VSS*d) for the 2-hour cycle.

GW recycling for toilet flushing (see photos): Treated and disinfected GW was stored in a black polyethylene reservoir. This reservoir is connected to the building of the Department of Rural Engineering (DRE) to feed four toilets at the ground floor. A dual pipe network was adopted with the valve of drinking water staying permanently closed except when GW is not available. Also and to prevent GW from flowing back into the drinking water network, a gap of 4 cm was left between the drinking water pipe and the highest water level in the flushing reservoirs (figure 4, where the drinking water valve was open for the purpose of the picture). Four similar toilets, located on the first floor of the DRE building, were flushed with potable water for comparison.

1.2. Hybrid-raw wastewater constructed wetland: A hybrid-three-stage Constructed wetland was implemented in April 2007 in the framework of the cooperation between IAV and University of Guelph in Canada. The system is based on the Cemagref design which normally include two vertical planted filters in series. Here, recycling to a horizontal-flow planted filter (located between the two vertical-flow filters, was added to achieve a better denitrification of the effluent. The unit is receiving 10 m3/day of raw wastewater , which is subjected to sand and coarse material removals.

Planted gravel filter and multilayer sand filter.

Dual network (greywater recycling /potable water) for toilet flushing

Monitoring results

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