Urban wastewater treatment in stabilization ponds: occurrence and removal of pathogens

doi:10.1016/S1462-0758(01)00071-1

Urban Water

Volume 4, Issue 3, September 2002, Pages 255-262

https://doi.org/10.1016/S1462-0758(01)00071-1 Get rights and content

Abstract

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.

Introduction

The growing urbanization in many areas of Morocco has resulted in a significant increase of generated amounts of urban wastewater. There is no doubt that urban wastewater effluents represent a valuable source of water and nutrients which may be reused to advantage in land irrigation systems. However, the transmissive stages of pathogens excreted in the feces of infected individuals, whether human or animal, may become a potentially pathogenic component of the wastewater. The degree of risk to public health which may be associated with wastewater reuse is related to the microbial characteristics of the effluents. In fact, there are several pathogenic microorganisms which can be transmitted via sewage and epidemiological studies have shown that reuse of raw wastewater for agricultural purposes increases the contamination level of irrigated crops and the prevalence of parasitic infections among the exposed populations (Amahmid, Asmama, & Bouhoum, 1999; Bouhoum & Schwartzbrod, 1998; Cifuentes, Blumenthal, Ruiz-Palacios, & Bennet, 1992). Different wastewater treatment processes have been used to limit sanitary risks related to wastewater (Feachem, Bradley, Garelick, & Mara, 1983; Shuval, Adin, Fattal, Rawitz, & Yekutiel, 1986). Stabilization ponds, as a result of their long retention times, have been considered as a well established method for removing parasites from urban wastewaters.

The current study aimed to determine the occurrence and removal of protozoan cysts and helminth eggs in municipal wastewater by a pilot of waste stabilization ponds under arid climate conditions in Marrakech (Morocco). For helminths, Ascaris eggs were chosen due to their high resistance to hostile environment factors (Feachem et al., 1983). For protozoa, Giardia cysts were retained because of the cosmopolitan character of this parasite implied in many waterborne epidemics (Constantine, Hales, & Dawson, 1995; Isaac-Renton, Moorehead, & Ross, 1995; Moore et al., 1994).

Section snippets

Pilot details

The studied stabilization ponds consist of two circular basins disposed in series, each of a superficial area of $2500 m^{2}$ and a depth of 2.3 m for the first basin and 1.5 m for the second, respectively (Fig. 1). Each basin contains a small island in the center and its bottom is rendered waterproof by a film of polyethylene $180 μm$ thick. The system is fed by urban wastewater forwarded by an earth canal of approximately 2 km. The wastewater flow at the system entrance varied according to seasons and

Investigation of wastewater

In raw wastewater, Giardia cysts were detected in 24/48 (50%) of samples taken at the station E₁ with a geometric average concentration of 2.8×10³ cysts/l and a range of 29––8.3×10³ cysts/l. Only 39.5% (19/48) of these samples contained Ascaris eggs with numbers ranging from 0.3 to 6.1 eggs/l with an average of 1.7 eggs/l (Fig. 2).

To examine the existence of a seasonal variation in parasite numbers in raw wastewater, two periods were defined, the cold period comprising Winter and Autumn and the

Discussion

The concentration of Giardia cysts in wastewater has been estimated in a number of studies at a variety of treatment works with a range of different catchment variables (Table 1). In general these studies suggest that in the contributory catchments for these sewage influents, Giardia cyst numbers are very variable. The study results seem to be in accordance with those reported by many investigators. However, the lack, at present time, of a standard method for the recovery and detection of

Conclusions

Giardia cysts were detected in 50% of raw wastewater samples with an average concentration of 2.8×10³ cysts/l, while Ascaris eggs were isolated in 39.3% of samples with an average of 1.7 eggs/l. The concentration of cysts and eggs varied according to seasons, with highly significant concentrations in the hot period. Wastewater treatment in waste stabilization ponds (16 days retention time) resulted in removing Giardia cysts and Ascaris eggs from the effluent. During the sewage treatment

Acknowledgements

Thanks to Dr. Tony Grimason, Division of Environmental Health, Department of Civil Engineering, University of Strathclyde, Glasgow, Scotland, for his assistance.

This research was supported by a grant of the European Union, Project SEM No. 03/204/017.

References (48)

O Amahmid et al.
The effect of waste water reuse in irrigation on the contamination of food crops by Giardia cysts and Ascaris eggs
International Journal of Food Microbiology
(1999)
R.M Ayres et al.
The accumulation, distribution and viability of human parasitic nematode eggs in the sludge of primary facultative waste stabilization pond
Transactions of the Royal Society of Tropical Medicine and Hygiene
(1993)
K.V Ellis et al.
Parasite ova and cysts in waste stabilization ponds
Water Research
(1993)
R.A Gibbs et al.
Pathogen die-off in stored wastewater sludge
Water Science Technology
(1995)
A.M Grimason et al.
Occurrence and removal of Ascaris sp. ova by waste stabilisation ponds in Kenya
Water Science Technology
(1996)
A.M Grimason et al.
Occurrence and removal of Giardia sp. cysts by Kenyan and French waste stabilization pond systems
Water Science Technology
(1996)
J.B Rose et al.
Removal of pathogenic and indicator micro-organisms by a full-scale water reclamation facility
Water Research
(1996)
S Wiandt et al.
Occurrence of Giardia sp. cysts during a wastewater treatment by a stabilization pond in south of France
Water Science Technology
(1995)
Z Alouini
Fate of parasites in five wastewater treatment plants in Tunisia
Revue des Sciences de l'eau
(1993)
Al Salem, S. S., & Tarazi, H. M. (1992). Wastewater reuse and helminth infestation in Jordan: A case of study. Regional...

J Bailenger

Valeur comparée des méthodes d'enrichissement en coprologie parasitaire

Le pharmacien Biologiste

(1962)

C.R Bartone

Reuse of wastewater at the San Juan stabilisation ponds: Public health, environmental and socio-economic implications

K Bouhoum et al.

Epidemiological study of intestinal helminthiasis in a Marrakech raw sewage spreading zone

Zentralblatt Hygiene Umweltmed

(1998)

L.W Casson et al.

Giardia in wastewater – Effect of treatment

Water Pollution Control Federation Research Journal

(1990)

E Cifuentes et al.

Biological health risks associated with the composting of wastewater plant sludge

Water Pollution Control Federation Research Journal

(1992)

C.L Constantine et al.

Outbreaks of Giardiasis caused by a contaminated private water supply in the Worcester area

Cross, S. S., & Strauss, M. (1985). Health aspects of nightsoil and sludge use in agriculture and aquaculture. Part I....

F Delmas et al.

Etude parasitologique des boues résiduaires de la station de traitement des eaux usées de Marseille

Bulletin de la Société Française de Parasitologie

(1989)

R.G Feachem et al.

Sanitation and disease: Health aspects of excreta and waste water management

(1983)

L Gassman et al.

Wastewater and Giardia cysts

Water Science Technology

(1991)

Graham, H. J. (1981). Parasites and the land application of sewage sludge. Research program for abatement of municipal...

A.M Grimason et al.

Occurrence and removal of Cryptosporidium spp. oocysts and Giadia spp. cysts in Kenyan waste stabilization ponds

Water Science Technology

(1993)

C.J Hu et al.

Pathogen densities in wastewater sludge treated by anaerobic digestion and dewatering

J Isaac-Renton et al.

Giardia cysts concentrations and infectivity: longitudinal community drinking water studies

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Urban wastewater treatment in stabilization ponds: occurrence and removal of pathogens

Abstract

Introduction

Section snippets

Pilot details

Investigation of wastewater

Discussion

Conclusions

Acknowledgements

International Journal of Food Microbiology

Transactions of the Royal Society of Tropical Medicine and Hygiene

Water Research

Water Science Technology

Water Science Technology

Water Science Technology

Water Research

Water Science Technology

Fate of parasites in five wastewater treatment plants in Tunisia

Revue des Sciences de l'eau

Valeur comparée des méthodes d'enrichissement en coprologie parasitaire

Le pharmacien Biologiste

Reuse of wastewater at the San Juan stabilisation ponds: Public health, environmental and socio-economic implications

Epidemiological study of intestinal helminthiasis in a Marrakech raw sewage spreading zone

Zentralblatt Hygiene Umweltmed

Giardia in wastewater – Effect of treatment

Water Pollution Control Federation Research Journal

Biological health risks associated with the composting of wastewater plant sludge

Water Pollution Control Federation Research Journal

Outbreaks of Giardiasis caused by a contaminated private water supply in the Worcester area

Etude parasitologique des boues résiduaires de la station de traitement des eaux usées de Marseille

Bulletin de la Société Française de Parasitologie

Sanitation and disease: Health aspects of excreta and waste water management

Wastewater and Giardia cysts

Water Science Technology

Occurrence and removal of Cryptosporidium spp. oocysts and Giadia spp. cysts in Kenyan waste stabilization ponds

Water Science Technology

Pathogen densities in wastewater sludge treated by anaerobic digestion and dewatering

Giardia cysts concentrations and infectivity: longitudinal community drinking water studies