IWA Publishing in conjunction with the International Water Association’s Young Water Professionals is happy to announce a new initiative spotlighting the work of Young Water Professionals and showing how the work published in IWA Publishing Journals can be useful to those beginning their careers in the water sector.
Our fourth spotlight blog is from An-Sofie Christiaens, a PhD student at KU Leuven. An-Sofie was selected for this blog post after attending a YWP Conference. You can connect with An-Sofie on LinkedIn.
An-Sofie had access to our entire journal portfolio for one month, and picked out some interesting papers to discuss, read her thoughts below! A big thank you to An-Sofie for participating!
Hello, I am An-Sofie, a 25-year old PhD student at KU Leuven. In my PhD I investigate the influence of surface-associated structural proteins called amyloid adhesins on flocculation of activated sludge in biological wastewater treatment. I typically spend my days in the lab identifying process conditions that enhance adhesin formation with the help of fluorescence-based monitoring tools. However, the COVID-19 regulations and subsequent temporary closure of the lab has given me some time to catch up on relevant literature, and, also read into some new topics. I have selected my top 5 most interesting finds to share with you in this blog post.
In their review paper from 2019, Mohammed et al. discuss the production of bioflocculants from waste streams for industrial applications. Indeed, extracellular polymeric substances secreted by bacteria, fungi, and algae have proven to be a renewable alternative to chemical flocculants. This review gives a fairly complete overview of how these bioflocculants can be produced from inexpensive media like solid and semi-solid waste (e.g., sugar beet molasses, rice bran), and wastewater. However, in this review, waste activated sludge is overlooked as a potential consortium of bacteria to produce the bioflocculants. Additionally, for researchers like myself, more focus on possible extraction methods of the bioflocculants from the organisms would be a useful addition. I believe that this type of paper can facilitate the transition from lab scale to industrial scale bioflocculant applications.
Bioflocculation is a critical step in many other biotechnological applications besides wastewater treatment. This also applies to microalgae harvesting as described in this article by Demir et al. (2020). Even though microalgae are a promising renewable energy source that can be cultivated on wastewater, its production and harvesting are currently economically unviable. While the use of synthetic flocculants can contaminate both the harvested biomass as well as recycled water, this review reports several natural flocculation methods as alternatives. The addition of bio-sourced flocculants such as natural polysaccharides is one option that is nicely in line with the above-mentioned paper by Mohammed et al. 2019. Another option is also mentioned as an alternative direction in natural flocculation: genetic engineering. This review paper discusses the successful insertion of the FLO5 gene encoding surface proteins, originally expressed in yeast, and microalgae. Personally, I find this a fascinating and powerful approach especially for high-end applications, although I acknowledge the controversy related to the use of GMOs. To conclude, this paper correctly states that the eventual bioflocculation performance is the result of a complex interplay between electrostatic, hydrophobic, and steric interactions.
Similar to flocculation, biofilm formation is a survival strategy for bacteria. While flocculation is wanted in activated sludge systems, biofilm formation is unwanted in drinking water systems. In both situations, understanding the formation and dynamics is key. Liu et al. (2020) investigated the effect of flow-induced shear on EPS production and composition in biofilms in drinking water distribution systems. They report that an intermediate velocity (1.0 m/s) enhances biofilm formation. To explain this result, the researchers investigated the EPS quantity and composition. More specifically they analyzed the surface hydrophobicity, extracellular polysaccharides and proteins, and zeta potential. These methods are all very black box. Therefore, I would suggest including more specific stainings to identify some of the proteins, such as Thioflavin T that targets amyloid adhesins. Indeed, it is hypothesized that amyloids exhibit a catch-bond behavior which plays a role in dynamic conditions.
Another paper that I enjoyed reading was this recent paper from 2020 where Agliamzanov et al. investigated the application of distributed computing for hydrological flood forecasting. Distributed computing, or the distribution of any kind of scientific computing task among participant devices, is a form of citizen science. Perhaps the most well-known example of distributed computing is the Folding@Home project, which aims to carry out protein folding simulations to enhance disease research projects. Agliamzanov et al. used this approach to forecast hydrological floods based on rainfall from climate projections. Keeping in mind the recent advances in high-resolution sensing and monitoring capabilities and the subject of “Internet of Water”, I look forward to many more applications of distributed computing and citizen science in the field of waste- and drinking water.
Finally, I came across this paper by Saravanan et al. (2019) that discusses the use of modified cellulose beads bearing chelating groups for the removal of heavy metals in wastewater. In this work, the effect of the pH, metal ion concentration, adsorbent dose, temperature, and equilibrium time on the removal of Cu(II) and Pb(II) ions is investigated. The adsorption capacity of this specific adsorbent for Cu(II) and Pb(II) was very high compared to other adsorbents. However, let’s keep in mind that (i) the ideal conditions used in the lab-scale batch tests are not likely to be fulfilled in full-scale applications, and (ii) real industrial wastewater will contain a mixture of heavy metals with varying concentrations. Therefore, I am looking forward to follow-up experiments with more realistic test setups. Overall, I like the idea of the use of cellulose as a cheap and renewable adsorbent, and I am wondering whether cellulose that is recovered from toilet paper could be used for this purpose.
Hopefully, you have enjoyed reading this spotlight blog where I have tried to highlight some new literature in the field of bioflocculation, as well as some topics that are outside of this field, for the sake of broadening my own (and your?) knowledge.
All the best,
ansofie.christiaens [at] kuleuven.be
Department of Chemical Engineering, KU Leuven
Implications for industrial application of bioflocculant demand alternatives to conventional media: waste as a substitute
Jibrin Ndejiko Mohammed, Wan Rosmiza Zana and Wan Dagang
Water Science & Technology (2019) 80 (10): 1807–1822.
Towards a better understanding of microalgae natural flocculation mechanisms to enhance flotation harvesting efficiency
Irem Demir, Alexandre Besson, Pascal Guiraud and Cécile Formosa-Dague
Water Science & Technology, April 2020.
Linking flow velocity-regulated EPS production with early-stage biofilm formation in drinking water distribution systems
Yanyan Liu, Rongrong Shan, Guowei Chen and Li Liu
Water Supply, March 2020.
Hydrology@Home: a distributed volunteer computing framework for hydrological research and applications
Ramil Agliamzanov, Muhammed Sit and Ibrahim Demir
Journal of Hydroinformatics (2020) 22 (2): 235–248.
Chelating modified cellulose bearing pendant heterocyclic moiety for effective removal of heavy metals
R. Saravanan, R. Mahalakshmi, M. S. Karthikeyan and L. Ravikumar
Water Science &Technology (2019) 80 (8): 1549–1561.