The removal of pathogens in surface-flow constructed wetlands and its implications for water reuse

Microbiological quality represents the biggest concern to the reuse of treated wastewater. This paper reports and discusses the results of an international survey on the removal of indicators of microbiological contamination in surface-flow constructed wetlands. Constructed wetlands consistently provide a reduction of 90–99% (1–2 log-removal) in the concentration of indicators such as coliform bacteria and faecal streptococci. This removal is found in wetlands treating water from different types of pretreatment (primary sedimentation, activated sludge, trickling filter, maturation ponds). On the other hand, when the influent is of high microbiological quality, wetlands act as sources of pathogenic contamination. The final water quality, however, is still compatible with medium to no-contact recreational activities and other final water uses. High variability in the effluent quality and seasonality might limit the opportunities for reuse. The role of constructed wetlands in different treatment schemes and the remaining open questions concerning removal mechanisms and reference pathogens are discussed.

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A survey of the microbial quality of wastewaters in Ismailia, Egypt and the implications for wastewater reuse

Water Science & Technology ◽

10.2166/wst.1997.0736 ◽

1997 ◽

Vol 35 (11-12) ◽

pp. 211-217 ◽

Cited By ~ 4

Author(s):

R. Stott ◽

T. Jenkins ◽

M. Shabana ◽

E. May

Keyword(s):

Constructed Wetlands ◽

Sewage Treatment ◽

Microbiological Quality ◽

Faecal Coliform ◽

Treated Wastewater ◽

Coliform Bacteria ◽

Intestinal Helminths ◽

Practical Applications ◽

Helminth Eggs ◽

Raw Wastewater

The occurrence of parasite ova, cysts and faecal coliforms in urban wastewater and their removal was determined after sewage treatment in gravel bed hydroponic (GBH) constructed wetlands receiving conventionally treated wastewater at Abu Attwa, Ismailia. Samples of raw wastewater and GBH influent and effluents were examined for eggs of intestinal helminths over two months in 1995. All raw wastewater samples were found to be positive for Ascaris lumbricoides but eggs of Hymenolepis spp, Trichuris spp, Ancylostoma duodenale and Toxocara spp were also detected in raw and conventionally treated wastewaters. In Ismailia, the concentration of eggs of human intestinal helminths in raw wastewater ranged from 6–42/L. In the influent to the GBH beds, the concentration of helminth eggs was reduced and ranged from 0–11/L; eggs of Ascaris were found in 28% of the samples. No helminth eggs were recovered from GBH treated effluents. Cysts of protozoa and faecal coliform bacteria were also removed by GBH beds to some degree. Raw wastewater contained cysts of the protozoa, Entamoeba coli, E. histolytica and Giardia spp. Although the density and diversity of species was reduced after treatment in the GBH beds, some amoebic cysts were found in the effluents. Faecal coliform removal averaged 2–3 logs during sewage treatment in GBH beds but effluents did not satisfy WHO guidelines for unrestricted irrigation. This survey indicates that GBH beds have the capacity to remove pathogens from wastewaters. Improvement in wastewater quality after GBH treatment satisfied WHO microbiological quality guidelines for restricted irrigation. With a retention time of 6h, GBH constructed wetlands have practical applications for wastewater treatment for safe reuse in Egypt.

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Enhanced nutrient removal and mechanisms study in benthic fauna added surface-flow constructed wetlands: The role of Tubifex tubifex

Bioresource Technology ◽

10.1016/j.biortech.2016.11.035 ◽

2017 ◽

Vol 224 ◽

pp. 157-165 ◽

Cited By ~ 18

Author(s):

Yan Kang ◽

Jian Zhang ◽

Huijun Xie ◽

Zizhang Guo ◽

Huu Hao Ngo ◽

...

Keyword(s):

Constructed Wetlands ◽

Nutrient Removal ◽

Benthic Fauna ◽

Surface Flow ◽

Tubifex Tubifex ◽

Surface Flow Constructed Wetlands

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IDENTIFYING THE MOST SUITABLE AREAS FOR SURFACE FLOW WETLAND CONSTRUCTION IN LITHUANIA

Proceedings of the 7th International Scientific Conference Rural Development 2015 ◽

10.15544/rd.2015.060 ◽

2015 ◽

Author(s):

Antanas DUMBRAUSKAS ◽

Nijolė BASTIENĖ ◽

Petras PUNYS

Keyword(s):

Constructed Wetlands ◽

Ecological Status ◽

Surface Flow ◽

Gis Analysis ◽

Proximity Analysis ◽

Wetland Construction ◽

The Mean ◽

Two Phases ◽

Terrain Features ◽

Surface Flow Constructed Wetlands

GIS-based approach to find the suitable sites for surface flow constructed wetlands was employed for the Lithuanian river basins with low ecological status. According to the nature of the analysed criteria the flowchart consists of two phases. Criteria used include hydrographical network, soil properties, terrain features, land use, etc. Some of them have strictly defined values (constraints), and other ranges within certain limits (factors). Limited criteria were analysed using rejection principle and influencing factors using proximity analysis and overlay methods. Selecting the potential sites using standard GIS analysis tools there was estimated about 3286 sites for possible wetlands with the mean area of inflow basin about 4 km2 in the basins of water bodies at risk.

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