Urban water cycles, water service delivery systems and removal of pollutants

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This session will include the speaker: Nienke Koeman-Stein (KWR), Jim Wright (School of Geography and Environmental Science, University of Southampton) and Kees Roest (KWR Water Research Institute, Nieuwegein, The Netherlands)

Take a look at the abstracts below:

Removal of organic micro-pollutants by recovered activated carbon from lactate production and drinking water production 

Presenting speaker: Nienke Koeman-Stein

The removal of organic micro-pollutants (OMPs) from (waste) water is becoming increasingly important. More and more medicine residues have to be removed from household wastewater. Horticultural companies must also extensively purify their waste water from used crop protection agents. 

Removal of organic micro-pollutants from water can be achieved using various technologies. It has been shown that fresh (unused) activated carbon is suitable for this. However, fresh activated carbon from coal is not a sustainable source. Therefore, we investigated whether the application of powdered activated carbon, which has already been used in drinking water production or in lactose production, is still suitable for the removal of organic micro-pollutants from municipal and horticultural wastewater. 

The aim of this TKI-project is to clarify whether the reuse of powdered activated carbon (PAC) from drinking water production or lactose production is feasible for the removal of organic micro-pollutants from waste water from a technological, economical and sustainable point of view. 

First findings are that the adsorption capacity is such that powdered activated carbon from drinking water production is still sufficient to justify the reuse for posttreatment of WWTP effluent and a comparable amount of activated carbon is required compared to fresh carbon (different type). The activity of PAC from drinking water production is comparable with a fresh carbon type (PAC-type which literature states: suitable for wastewater). Results show that the PAC from lactose production has limited adsorption capacity left, as was suspected. However, application in the activated sludge tank is still under investigation. The activated sludge might increase the adsorption capacity by  (partly) reactivating the PAC.  

As part of the study safety issues, such as desorption of components (PFAS, organics) and safety of dosing, are investigated. Furthermore a LCA study will be conducted to determine the environmental impact of recycled (from drinking water production of lactose production) carbon compared to fresh activated carbon (from coal). A technical and logistical feasibility analysis and an economic evaluation are also part of this project. 

This activity is co-financed with public-private-partnership financing for Top Consortia for Knowledge and Innovation (TKIs) from the Ministry of Economic Affairs and Climate. 

Circular Water 2050 – Impact and opportunities of a fully circular urban water cycle 

Presenting author: Kees Roest

A vision and roadmap for the water sector was developed, with a view to the national ‘A Circular Economy in the Netherlands by 2050’ program. This involved the raw material efficiency in the urban water cycle, including the extraction and reuse of raw materials. An overview of possible conceptual and technological innovations that can be relevant for the water cycle in 2050, including an inspirational illustration, has been produced. Also a tool with 16 characteristics to monitor and evaluate circularity has been developed. Finally a circular system integration is needed. We investigated, described, discussed, defined and established what is meant in the water cycle with fully circular in 2050 and how this can look like in practice. Via back casting the steps and open questions to reach circularity in 2050 have been defined. 

Area selection for post-hoc impact evaluation of the delegated management model of urban water service delivery in Kisumu, Kenya 

Presenting author: Jim Wright

Background: Delegated management, also known as a water operator partnership, is a model under which a utility delegates operational responsibility for urban water services to a small-scale provider.  This decentralised service delivery model is currently operational in parts of Maputo(Mozambique), Arusha ( Tanzania), and Kisumu in Kenya.  To date, studies of the delegated management model’s impact have focused on service expansion, pipeline breakages and supply interruptions, and revenue recovery, but not its water quality impacts, nor systematically examined neighbourhood characteristics where delegated management has been implemented. 

Aim: This study therefore aims to evaluate delegated management’s impact on microbiological water quality in Kisumu by drawing a sample of enumeration areas (EAs) for follow-up fieldwork, comprising delegated management sites and control EAs with matching characteristics. 

Methods: This post hoc impact evaluation study will ultimately compare E. coli contamination of kiosk and household stored water in a matched sample of EAs under delegated management versus a control group. In this phase, EAs under delegated management were identified via utility records and relevant EA characteristics (including metered water connections/household; kiosks/capita; population density; proximity to sewerage lines; and probability of built-up land cover) were collated within a GIS from census data, utility records, and satellite imagery.  To minimise differences between EAs under delegated management and comparator control EAs, a balanced sample of EAs was selected using coarsened exact matching, a technique used to reduce imbalance when sampling for such impact evaluation studies.  Matched EAs neighbouring delegated management areas were excluded from the selection, so as to minimise spatial spillover effects in the subsequent evaluation. 

Results: Of 987 urban EAs in Kisumu County, 402 either lacked piped water or neighboured delegated management areas, so were excluded.  Among remaining EAs, there was joint imbalance in the characteristics of those under delegated management versus the remainder (L1=0.74). The 217 delegated management EAs were more densely populated with fewer metered connections/household, had a 23% greater mean probability of built-up land cover, and 20% fewer were located near sewerage piplines than the remaining EAs. Via coarsened exact matching, 139 delegated management EAs and 144 control EAs were successfully matched. In this selection, joint imbalance was reduced (L1=0.48), with delegated management EAs having 8% greater probability of built-up land cover and the same proportion located near mains sewerage as control EAs. 

Conclusions: These findings show EAs under delegated management are more densely populated, built-up, and further from mains sewerage than those directly managed by the utility.  A matched sample of EAs was identified to control for these differences via a subsequent impact evaluation study. This matched sample could also be used to target further expansion of delegated management as a decentralisation strategy for service delivery. The coarsened exact matching technique has potential for wider use in water sector impact evaluation studies. 

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