Wastewater biorefineries involve the recovery of valuable products, including water and nutrients, from wastewater. Wastewater treatment systems represent a critical step in the increasing focus on resource efficiency, and potentially provide a link between the users of water and those responsible for its management where resources are recovered in closed loop cycles.
Ultimately the use of wastewater biorefineries should lead to an optimisation strategy for maximising efficiency of waste treatment and of bioresource utilisation in terms of economic, environmental and social impact.
This concept was born from a lifetime of thinking (communicated by Prof Sue Harrison) and research (lead by her and coworkers in the Centre for Bioprocess Engineering Research (CeBER), based at the University of Cape Town), and was eventually articulated through this partnership, funded by the Water Research Commission.
Our first report has been published, and is available for download for free at the Water Research Commission website: Introducing the wastewater biorefinery concept
Authors: Verster B; Madonsela Z; Minnaar S; Cohen B; Harrison STL;
2014/02/01; Research Report No.TT 587/13
(There is also a copy via Dropbox if the above link gives trouble)
Wastewater treatment plants represent a source of nutrients for microbial growth and product formation. In an approach in which bioresource productivity is maximised, it is desirable to not only achieve water treatment to the desired standard, but at the same time to harness the value in these resources. Wastewaters are a source of nutrients such as C, N and P. Macro-nutrients typically comprise the major share of the operating costs of commodity bioprocesses, such as the production of alcohols, organic acids and polymers. The nutrient loads in municipal wastewaters are dilute, but add up to significant daily loads because of the massive volumes generated in urban populations. Bioprocessing to reduce these nutrient loads in wastewater while producing a range of byproducts have conventionally included biogas and compost, produced with minimal modification of existing plants.
In extending the potential product range of these ‘wastewater biorefineries’, key design factors include the following: using waste resources in a non-sterile environment, thus requiring a positive selection pressure for the product of interest; and producing a product that is readily separated from the wastewater through a phase change such as precipitation. Stress and storage polymers satisfy both these requirements.
In such systems, the tension between the environmental biotechnology focus on resultant water purity and the industrial biotechnology focus on the additional products needs to be resolved. In this approach, it is accepted that water quality will take precedence; however, by introducing the product focussed unit operation within the multi-unit process, combined optimisation has potential to allow concomitant achievement of both goals.
While we translate this into plain language, have a look at other, also very technical, posts on the matter:
- Biotech in Sanitation: Working towards Wastewater biorefineries
- PhD report: Executive summary
- PhD report: closing remarks
We are currently researching wastewater biorefineries in greater detail through another Water Research Commission funded project (WRC Project Number: K5/2380). Watch this space, and please get in touch with any comments or inputs on wastewater beneficiation globally - firstname.lastname@example.org