Nutrient and Precious Metal Recovery from Wastewater Systems

Water and wastewater treatment systems provide natural aggregation points for rapid and effective harvesting of nutrients, particularly phosphorus, and precious metals. This project aims to use smouldering for nutrient and precious metal recovery from wastewater treatment solids. Smouldering was developed as a remediation process for contaminated soils; here, it is proposed as a volume reduction and treatment process for wastewater biosolids. Because it uses the energy inherent to the biosolids, smouldering has the potential to reduce operating costs and improve value recovery.

Based on century-old technology, conventional wastewater treatment was designed to meet public health needs without more modern concerns of energy efficiency and resource recovery. Sludge treatment in particular is an energy-intensive and time-consuming process that accounts for up to 50% of total treatment plant costs. Smouldering of wastewater biosolids offers a 21st Century solution that will achieve the goals of rapid, energy-efficient treatment and resource recovery (e.g. phosphorus, biofuel, etc) without sacrificing the desired public health outcomes. Smouldering is an exothermic surface combustion phenomenon that uses the energy inherent within the biosolids as fuel, reducing energy costs while enabling resource recovery during treatment. Because it is exothermic, energy efficiency tends to increase with operating scale. Resource recovery is possible from process emissions generated during and residual ash remaining after smouldering. Experience with smouldering for soil remediation suggests that the process is particularly promising for harvesting phosphorus either through collection of condensate from process emissions or formation of residual ash that releases phosphorus slowly into water leachate. Temperatures are much higher for soil remediation than would be expected for biosolids treatment, so nitrogen recovery in condensate and/or ash may be possible as well. As with any combustion process, the extremes of operating conditions, particularly oxygen-lean conditions, may be associated with by-product formation; these conditions should be identified and avoided. This project addresses the critical knowledge gap of how operating conditions affect nutrient harvesting, precious metal recovery, and co-contaminant fate that are important to understand ahead of developing industrial-scale smouldering processes for biosolids treatment. Studying process emissions is of particular importance from a regulatory point of view.

The overall aim of this project is to evaluate the ability to harvest nutrients and precious metals from wastewater treatment biosolids under varying operating conditions. The specific objectives of this project are:
(1) Identify suitable test methods for total and available phosphorus in biosolids;
(2) Evaluate the range of operating conditions (e.g. water content, smouldering parameters) to optimise nutrient harvesting and precious metal recovery; and
(3) Determine the impacts of operating conditions on co-contaminant presence, availability, and/or potential formation in emissions and residual ash.
This project will use advanced analytical methods such as induction coupled plasma optical emission spectroscopy and/or mass spectrometry (ICP-OES, ICP-MS) and chromatographic techniques such as comprehensive two-dimensional gas chromatography (GCxGC) in order to study fate and availability of nutrients, precious metals, and co-contaminants.
Research outcomes and links to industry: This transformative project is anticipated to lead to publications in high quality academic journals as well as fundamental knowledge necessary for the design of improved wastewater treatment infrastructure for energy savings and material harvesting in the near future.
Candidate background: The ideal candidate will have a background in chemical, environmental, or mechanical engineering; environmental or analytical chemistry; or applied biogeochemistry.