From unplanned to planned agricultural use: making an asset out of wastewater

Abstract

Urban wastewater is increasingly used for agricultural production, particularly in those areas where access to fresh water resources is limiting. Depending on the prevailing institutional arrangements, this agricultural use is planned or unplanned. If planned, a general policy is to minimise health risks and environmental pollution, leading to an often centralised collection of the city's sewage, followed by primary, secondary and further treatment until the prevalent discharge effluent use standards are met. If society can afford them, advanced treatment technologies are installed, backed by a well functioning institutional infrastructure. In contrast, in less prosperous countries the agricultural use of wastewater is driven by the high needs for water and the absence of affordable fresh water resources along with insufficient financial means to construct treatment systems and distribution networks that comply with the official regulations. Combined with a poor institutional framework, this results in unplanned and unguided direct or indirect use of raw, partially treated or diluted wastewater. In an effort to mitigate health and environmental problems, we propose using a reverse water chain design approach, in which the ultimate fate of the water is the basis for the design of conveyance and treatment facilities.

Discussion on Sustainable Water Technologies for Peri-Urban Areas of Mexico City: Balancing Urbanization and Environmental Conservation

“…With letting the final users determine the quantitative and qualitative water requirements needed for a specific purpose such as agriculture, industry or (nonpotable) household activities, the user or purpose of the wastewater determines the quality to which the wastewater is improved, which is the opposite of the conventional water chain where governmental legislation or permits dictate the treatment level. This reverse water chain [9][10][11], results in a new and novel view of waste and wastewater treatment and water sourcing where legislation should allow for tailor-made solutions. This may also reduce costs as not all waste and wastewater need to be treated up to high standards, since a part can also be used for purposes only requiring lower standards.…”

Use of (partially) treated municipal wastewater in irrigated agriculture; potentials and constraints for sub-Saharan Africa

“…Also, the quantity and quality of water is rapidly reducing across countries in sub-Saharan Africa (Freitas, 2013), resulting in growing water shortages due to increasing water demands for food production as well as industrial and domestic use (Rockstr€ om et al, 2010). The agriculture sector is by far the largest freshwater user, and thus, water reclamation for irrigation is an alternative that might reduce pressure on freshwater resources, particularly near and in urban areas, while also preventing non-controlled wastewater discharges to the environment (Pedrero et al, 2010;van Lier and Huibers, 2010). In addition, urban water reclamation is an opportunity to reduce the use of artificial fertilizers, which can serve as an economic benefit to (poor) farmers and help to improve their livelihood.…”

“…In addition, guidelines that only take into consideration the water quality at the point of use are unrealistic for the current situation of many African cities and countries. On the long term, there is a need to balance the treatment level with the required water quality level (van Lier and Huibers, 2010). Within this approach, the required water quality at the farmer's level would set the boundary conditions for the treatment system, while combining the use of treated wastewater with other protective measures and master planning.…”

“…As a result, urban farmers often struggle to obtain high quality irrigation water because of competition with potable uses (Moglia, 2014). However, in urban areas, alternative (low-grade) water sources are generally available, such as wastewater originating from households, industries, and storm water (Toze, 2006;van Lier and Huibers, 2010). These alternative sources have frequently been studied for use in agricultural irrigation (Roon, 2007;Srinivasan and Reddy, 2009;van Rooijen et al, 2010;Villamar et al, 2018).…”

The Use of (Treated) Domestic Wastewater for Irrigation: Current Situation and Future Challenges

“…There are some examples of guidelines for water reuse [49], but the most common standards in many countries, particularly developing ones, have been influenced by the World Health Organization [10,79]. Some studies have called for a more flexible legal framework, less worried about issues of potential liability and more focused on the integral analysis of the water chain [110,118]. An incremental approach for the introduction of water quality standards is recommended, particularly for countries with high levels of excreta-related diseases and deficient wastewater treatment systems [10,119].…”