ZeroWasteWater: short-cycling of wastewater resources for sustainable cities of the future

Abstract

Actual sewage treatment relies on conventional activated sludge (CAS), which reaches sufficiently low carbon, nitrogen and phosphorus effluent levels, but is not cost-effective, hardly achieves recovery, requires electricity equivalent to a fossil fuel consumption of 85 kWh per inhabitant equivalent (IE) per year and has an operational CO 2 footprint of 80 kg CO 2 IE −1 year −1 . Projected water and phosphorus shortages and the need to lower greenhouse gas emissions force us to rethink wastewater treatment for sustainable cities of the future. ZeroWasteWater offers an approach to short-cycle water, energy and valuable materials while adequately abating pathogens, heavy metals and trace organics. A less diluted waste stream will be obtained from sewerage improvements, a more rational use of potable water and the addition of ground kitchen waste, complemented by an advanced physicochemical or/and biological concentration step at the entry of the sewage treatment plant. Anaerobic digestion will recover electricity from the concentrated stream and further treatment will render a value of 6.2 EUR IE −1 year −1 under the form of the nutrients nitrogen and phosphorus, and the carbon-sequestrating biochar. In the water stream, residual nitrogen will be removed through partial nitritation and anammox, followed by heat recovery and add-on membrane technologies yielding potable water (> 65 m 3 IE −1 year −1 ). Overall, compared to a CAS system without sludge digestion, the recovery of energy and nutrient in ZeroWasteWater avoids a fossil fuel use of 439 kWh IE −1 year −1 and an operational emission of 88 kg CO 2 IE −1 year −1. Interestingly, such approach is expected to be economically viable. The key challenges remain to incorporate water chain management in holistic urban planning and to render a cradle to cradle approach which society will find acceptable.

Prospects of Source-Separation-Based Sanitation Concepts: A Model-Based Study

“…Due to the significant energy gain from the grey water effluent reuse, grey water treatment in the SBR becomes energetically more favorable than bio-flocculation of grey water in the A-trap and subsequent grey water sludge co-digestion in the UASB reactor. Besides water and nutrient recovery, there is an increasing interest to recover the heat content of wastewater [44]. Heat recovery on-site from source-separated grey water using a heat exchanger would be an energy-efficient option to preheat the incoming tap water, as no electricity is needed.…”

Integrating Process and Factor Understanding of Environmental Innovation by Water Utilities

“…To achieve this, water utilities not only need to innovate in relation to the adoption of new technologies (Daigger 2012;Kujawa-Roeleveld and Zeeman 2006;Verstraete and Vlaeminck 2011), but also with respect to non-technical approaches including catchment management and the management of decentralised water and wastewater services (Daigger 2012;Dolan et al 2014). In order for regulation and utility management to influence innovation pathways it is essential to understand the processes and the factors that affect the selection of types of innovations of most relevance to water and sewerage utilities.…”

A two-stage decentralised system combining high rate activated sludge (HRAS) with alternating charcoal filters (ACF) for treating small community sewage to reusable standards for agriculture

“…Therefore, efficacious and cost effective technology to boost wastewater reuse and recycling needs development for the developing world. Verstraete and Vlaeminck (2011) proposed a new approach for optimal resource recovery, as opposed to the conventional wastewater management. In this approach which they label as the M & M treatment system, the wastewater is separated as near as possible to the source into two distinct streams: the major line (up to 90% of the flow) and the minor line (about 10% of the flow).…”