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Pathogenic enteric parasites are the major health concern associated with sewage reuse in irrigation. Therefore, reduction of these agents is recommended to prevent any risks for human health. The present study was designed to evaluate the occurrence and persistence of pathogenic parasite eggs and cysts in a constructed overland flow and percolation plant. The pilot was operated at a flow rate of 0.02 m3 s−1 with a hydraulic loading of 0.21 m3 m−2 d−1. The found results demonstrated that the process was effective in the removal of eggs and cysts from treated wastewater with rates up to 100%. During the treatment process cysts and eggs concentrate in soil with mean numbers of 2.8 × 104 cysts/100 g d.w (dry weight) and 37.5 eggs/100 g d.w, respectively, with decreasing levels from the system’s inlet toward the outlet. Also, eggs and cysts were found to percolate in soil but not greater than 12 cm of depth. Crops grown on soil were contaminated with averages of 1.7 × 103 cysts/kg and 0.9 eggs/kg. Ascaris and Trichuris eggs developed in soil, mainly during the hot period, and 19.8% attained the infective stage. Helminth eggs persisted for longer periods in soil reaching over 3 months versus few days for protozoan cysts. Relatively shorter persistence periods were seen on crops with 9 days for eggs versus 6 days for cysts.

Waste stabilization ponds are frequently considered as being effective for the removal of intestinal parasites while conventional wastewater treatment processes are not. Over a 24-month period, grab samples from a pilot stabilization pond system in Marrakech were analyzed for the presence of Giardia cysts and Ascaris eggs. Giardia was isolated with an average of 2.8×103 cysts/l, while Ascaris eggs were detected with a mean number of 1.7 eggs/l. The data also suggest seasonal differences in Giardia cyst and Ascaris egg concentrations in raw wastewater, recording high monthly mean numbers during dry period (Spring and Summer). At the outlet of the system, neither Giardia cysts nor Ascaris eggs were found in treated wastewater. Enumeration of Giardia cysts and Ascaris eggs in the sediment at the entrance of the system resulted in average numbers of 1.3×103 cysts/g and 29.6 eggs/g dry weight of sediment. These concentrations decreased towards the outlet of the ponds where the sediment was free of Giardia cysts and Ascaris eggs.

The present study aimed to determine the occurrence and removal of protozoan cysts and helminth eggs from municipal wastewater by pilot waste stabilisation ponds in the arid climate of Marrakech (Morocco). Protozoan cysts detected in raw wastewater at the entrance of the system were identified as Entamoeba histolytica, Giardia sp. and Entamoeba coli at a mean concentration of 1.5×104 cysts/l. Helminth eggs identified were Ascaris, Trichuris, Hymenolepis, Enterobius and Taenia with an average of 7.6 eggs/l. The effluent at the system outlet did not contain detectable cysts or eggs. Sludge samples collected in the pond basins resulted in detection of protozoan cysts and helminth eggs. Sedimentation therefore seems to be the main factor for cyst and egg elimination during wastewater treatment by waste stabilisation ponds. This phenomenon leads however to parasite accumulation in the sediment.

In Marrakech, raw sewage has been used for farming purposes for several decades for many types of crops. This study aimed to determine the contamination level of Giardia cysts and Ascaris eggs for crops designated for human consumption. Collected crops in irrigated fields were turnip, marrow, squash, potatoes, pepper and eggplant. Field trials were also carried out on four crops, coriander, carrots, mint and radish, using three water types for irrigation, i.e. raw waste water, treated waste water (sedimentation and 16 days retention) and fresh water. Giardia cysts were detected at a level of 5.1 cysts/kg in potatoes, while Ascaris eggs were observed in numbers varying between 0.18 eggs/kg in potatoes and 0.27 eggs/kg in turnip. Field trials confirmed that irrigation of crops by raw waste water leads to contamination. Giardia and Ascaris were isolated in coriander at concentrations of 254 cysts/kg and 2.7 eggs/kg, respectively; mint was also highly contaminated with numbers reaching 96 cysts/kg and 4.63 eggs/kg. Carrots and radish were contaminated and respective numbers observed for Giardia were 155 and 59.1 cysts/kg; Ascaris was discovered in numbers of 0.7 and 1.64 eggs/kg, respectively. However, cultures irrigated with treated waste water and fresh water were free from contamination. Cysts and eggs on coriander persisted for a maximum of 8 days.

The present study consists of assessing the efficiency of a macrophyte (Phragmites australis) system in wastewater purification in an arid climate. The experimental system is made up of three beds differing in length (30, 40 and 50 m) and implanted with Phragmites australis. Wastewater inflow through these beds is horizontal with a flow of 10 l.s−1. Retention time varies between 1 and 4 h. The frequency of irrigation is weekly. The studied parameters are: the organic load (COD and TSS), nutrients (total Kjeldhal nitrogen: TKN and total phosphorus: TP) and the parasitical load (helminth eggs). Water, soil and plants are the three components of the experimental system we analyzed. Results reveal that in the output, the decrease in organic load, nutrients and parasitical load is very sharp in the large bed (COD: 62%, TKN: 43%, TP: 14%, helminth eggs: 93%). However, in the small bed (30 m), the decrease is slight (COD: 48%, TKN: 23%, TP: 5%, helminth eggs: 88%). Concerning parasitical load, the study shows that the three beds are effective in eliminating helminth eggs, even with a very short retention time (1–4 h). The quality of the effluent of the reed bed system should be classified within category B according to WHO guidelines (1989) for crops irrigation. Soil sample analysis from entrance to exit shows a decreasing gradient of nitrogen (N), phosphorus (P), organic carbon (Org.C), organic matter (OM) and parasitical helmith eggs. The gradient becomes more significant in the largest bed with decreasing rate, reaching respectively 49%, 44%, 37%, 40% and 100% for TKN, TP, Org.C, OM and helminth eggs. As for the plant material, the composition of major elements (nitrogen and phosphorus) of Phragmites aerial parts shows the same evolution. While the decreasing rate of nitrogen in the leaves reaches 50% in the largest bed, it does not exceed 8% in the smallest bed. Mean aerial productivity of the studied reed beds was estimated at 134 tons dry weight.ha−1. The aerial biomass exported contains only 5–6% of nitrogen and 10–12% of phosphorus with regard to their load at the influent.