Wetlands for wastewater treatment and subsequent recycling of treated effluent: a review

Abstract

Due to water scarcity challenges around the world, it is essential to think about non-conventional water resources to address the increased demand in clean freshwater. Environmental and public health problems may result from insufficient provision of sanitation and wastewater disposal facilities. Because of this, wastewater treatment and recycling methods will be vital to provide sufficient freshwater in the coming decades, since water resources are limited and more than 70% of water are consumed for irrigation purposes. Therefore, the application of treated wastewater for agricultural irrigation has much potential, especially when incorporating the reuse of nutrients like nitrogen and phosphorous, which are essential for plant production. Among the current treatment technologies applied in urban wastewater reuse for irrigation, wetlands were concluded to be the one of the most suitable ones in terms of pollutant removal and have advantages due to both low maintenance costs and required energy. Wetland behavior and efficiency concerning wastewater treatment is mainly linked to macrophyte composition, substrate, hydrology, surface loading rate, influent feeding mode, microorganism availability, and temperature. Constructed wetlands are very effective in removing organics and suspended solids, whereas the removal of nitrogen is relatively low, but could be improved by using a combination of various types of constructed wetlands meeting the irrigation reuse standards. The removal of phosphorus is usually low, unless special media with high sorption capacity are used. Pathogen removal from wetland effluent to meet irrigation reuse standards is a challenge unless supplementary lagoons or hybrid wetland systems are used.Electronic supplementary materialThe online version of this article (10.1007/s11356-018-2629-3) contains supplementary material, which is available to authorized users.

Assessing the environmental and economic efficacy of two integrated constructed wetlands at mitigating eutrophication risk from sewage effluent

“…Conversely, the River Mun ICW had a mean HRT of just 3.1 days, thus below the recommended period, because of a comparatively high outflow rate (187.1 m 3 /day) relative to the total volume (580 m 3 ). Previous studies have reported poor phosphorus removal performance when HRTs are short because of insufficient contact time between the sewage effluent and the sediments limiting phosphorus sorption and deposition (Almuktar et al, 2018); however no evidence of this was detected here. The HLR was also higher (0.055 m/ day) than recorded at the River Ingol ICW, although it was still below the recommended maximum of 0.1 m/day.…”

“…Typically consisting of a series of interconnected ‘cells’ or pools, ICWs are unlined, free surface flow systems characterised by shallow water depths (~20–40 cm), emergent vegetation and a bed constructed from in situ soil rather than artificial liners as typically found in non‐integrated constructed wetland designs (Harrington et al ., 2007; Kadlec et al ., 2010). ICWs are planted with a range of native aquatic plants which support diverse periphyton communities that act as important biofilters, absorbing excess nutrients from sewage effluent and reducing water velocities to encourage sedimentation of entrained particulate material (Almuktar et al ., 2018; Cooper et al ., 2019). With the additional aim of enhancing biodiversity and ‘integrating’ into the local environment, ICWs are designed to be environmentally sustainable, robust and largely self‐managing, thus making them a cost‐effective pollution mitigation option (Scholz et al ., 2007a).…”

Phytoremediation of Industrial Waste Leachates by Planted Filters Composed of Phragmites australis (Cav) Trin ex Steud, Typha latifolia L. and Cyperus papyrus L.

“…The reduction of nitrates, phosphates and heavy metals (Ni, Cd, Cr, Zn, Cu, Pb) in effluent leachates after passing through the reed plant filters was also highlighted, but their rate of abatement does not exceed 75%. These results appear to be an interessant alternative for the treatment of industrial wastewater by filters planted [41] with Phragmites australis (Cav) Trin ex Steud, Typha latifolia L. and Cyperus papyrus L. even though the salinity related to the nature of the wastewater somewhat reduces their purification capacity over time. However, we need to achieve absorption isotherms by the different plants and their kinetics of extraction of heavy metals to confirm the hypperaccumulator nature of the 3 plants chosen in this study.…”

Removal efficiency of nitrate, phosphate, fecal and total coliforms by horizontal subsurface flow-constructed wetland from domestic wastewater

“…It is demonstrated that the phenomenon of treatment is related to sedimentation, adsorption, biotic processing, and nutrient retention (20). However, an increase in HRT implies that the increase of the surface area of the gravel and, as a result, a larger total root surface area is available to support aerobic bacteria.…”