Sustainable Production of Reclaimed Water by Constructed Wetlands for Combined Irrigation and Microalgae Cultivation Applications

Abstract

Considering the increasing pressure on freshwater resources due to the constant increase in water consumption and insufficient wastewater control and treatment, recovering wastewater is a path to overcoming water scarcity. The present work describes the potential of reusing treated wastewater (reclaimed water) for irrigation and production of microalgae biomass in an integrated way, through experimental evaluation of plant and microalgae growth, and creation of an application model. First, two parallel experiments were conducted to evaluate the use of reclaimed water produced by a constructed wetland filled with a mix of solid waste: the irrigation of a set of small pots filled with soil and planted with Tagetes patula L., and the cultivation of microalgae Chlorella sp. and a mixed microalgae population with predominant species of the genus Scenedesmus sp. in shaken flasks and tubular bubble column photobioreactors. Results indicated no negative effects of using the reclaimed water on the irrigated plants and in the cultivated microalgae. The growth indicators of plants irrigated with reclaimed water were not significantly different from plants irrigated with fertilized water. The growth indicators of the microalgae cultivated with reclaimed water are within the range of published data. Second, to apply the results to a case study, the seasonal variability of irrigation needs in an academic campus was used to propose a conceptual model for wastewater recovery. The simulation results of the model point to a positive combination of using reclaimed water for the irrigation of green spaces and microalgae production, supported by a water storage strategy. Water abstraction for irrigation purposes can be reduced by 89%, and 2074 kg dry weight microalgae biomass can be produced annually. Besides the need for future work to optimize the model and to add economical evaluation criteria, the model shows the potential to be applied to non-academic communities in the perspective of smarter and greener cities.

Contribution of Constructed Wetlands for Reclaimed Water Production: A Review

“…The authors mention an ongoing study of a full-scale threestage plant consisting of horizontal subsurface CWs, an up-flow vertical flow CW, and a free surface flow CW. Pinho and Mateus [59] proposed the use of reclaimed water treated by a pilot-scale modular CW for combined irrigation and microalgae production. Although several works focused on the use of algae to treat and recover wastewater, there are no other examples of using reclaimed water produced by CWs.…”

Remote Monitoring of Energy-Autonomous Constructed Wetlands

“…Affordable means for wastewater treatment can avoid threats to freshwater availability for basic human needs, crops, and feed production, can avoid diseases and negative environmental impacts, and can potentiate the reuse of the treated wastewater [5][6]. Reclaimed water, as usually the recovered treated wastewater is named, can be used for diverse applications, such as irrigation, washing, fire control, and process water in the industry [7][8][9][10][11][12]. All applications of reclaimed water contribute to diminishing the abstraction of water from nature.…”

“…Due to the need for sustainable and low-impact technologies, nature-based solutions (NBS) are being considered as an alternative to conventional technologies [13,14]. Among NBS, CW is an affordable and greener technology for wastewater treatment [10,11].…”

“…119 of 2019; EU Regulation 2020/74 of the European Parliament and the Council of 25 May 2020 on minimum requirements for water reuse). Usual water quality parameters include physical parameters, such as suspended solids, electrical conductivity, and temperature, chemical parameters, such as such as pH, nutrients (nitrogen and phosphorous compounds), and chemical oxygen demand, and biological parameters, such as biochemical oxygen demand, and pathogenic microorganisms [10,18]. CW monitoring, like the monitoring of conventional wastewater treatment technologies, is typically made by the evaluation of the water quality parameters in chemical laboratories, after samples collection on site.…”

Considerations Related to the Application of the EU Water Reuse Regulation to the Production of Snow from Reclaimed Water

“…Therefore, it is very important to relieve the most valuable water resources. In selected areas, the water recovery from domestic waste water can be reused consisting of a solution for the water management enhancement [6] and an important part of the circular economy, closing the local water cycle [7][8][9].…”