Abstract
This paper reports on the performance of using a multistage constructed wetland (CW) to treat municipal raw wastewater and an analysis of its suitability for agricultural irrigation. The pilot plant consists of two stages of vertical flow CWs plus one stage of a horizontal CW built in 2018 with different local materials at the Gaston Berger University Campus, Saint Louis (Senegal). Each CW stage is composed of several filters with different type of media (silex, granite, or river gravel), filtering media depths, and macrophytes (Phragmites and Typha). The physicochemical and microbiological indicators were monitored over six months at each bed inlet and outlet to evaluate the efficiency and achievements of the Senegalese, European, and WHO regulations/recommendations for disposal or reuse in irrigation. This study demonstrates the viability of this new multistage CW design to treat raw municipal wastewater and produce an effluent of good quality suitable for reuse in agriculture. The removal of organic matter, suspended solids, and nutrients was very high (>95% for SS, BOD5 and N-NH4+, >90% for COD and P-PO43−), as was the reduction of microbiological indicators (fecal coliform reduction >5 log units and helminth egg removal of 100%). First, trends related to the influence of design (the type of gravel, filter depth, and type of macrophyte), operational modes, and the CW treatment efficiency were determined. The use of non-crushed gravel and Typha spp. seemed to provide better removal rates. On the contrary, no differences were found between the use of silex or granite gravel. For the studied Senegalese conditions under dry and hot climates, the preliminary results indicate that no resting periods are necessary for vertical flow CWs (VFCWs), thus resulting in a reduction in construction and operation costs. The main outcome of our study is evidence that multistage CWs can provide robust, cost-effective treatments, as well as allow for safe water reuse, which is imperative in areas with severe water scarcity and endemic microbiological waterborne diseases.
Highlights
According to the United Nations’ 2017 World Water Development Report [1], close to 80% of the wastewater generated by anthropogenic activities returns to nature without being treated or reused
This study demonstrates the viability of combining different types of constructed wetland (CW) to treat raw municipal wastewater with loads up to 72 g of SS/m2· day and 199 g of Chemical Oxygen Demand (COD)/m2 ·day
The combination of the three stages of CWs generated effluent with good quality suitable for discharge in the media or reuse in agriculture
Summary
According to the United Nations’ 2017 World Water Development Report [1], close to 80% of the wastewater generated by anthropogenic activities returns to nature without being treated or reused. Some pilot projects on treated wastewater reuse have been implemented, this type of reuse is still not common practice in Senegal, since the majority of the population does not have a sanitation system able to produce good quality water [4] From this perspective, constructed wetlands (CWs) could provide an effective solution to fulfill the legal requirements for low operation and maintenance costs. FRB configurations do not achieve a significant removal of microbial indicators [10,11], resulting in a problem in their implementation when reusing wastewater for certain applications that require low pathogen content (e.g., non-restricted irrigation) To address this gap and increase the reduction of bacterial pathogens without adding “conventional” or “advanced” technologies This paper reports on the first 6 months of performance for this multistage CW, as well as an analysis of its suitability for agricultural irrigation reuse
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
