Dr Raffaella Villa

Job: Reader in Environmental Engineering

Faculty: Technology

School/department: School of Engineering and Sustainable Development

Address: De Montfort University, The Gateway, Leicester, LE1 9BH, United Kingdom

T: 0116 255 1551

E: raffaella.villa@dmu.ac.uk

W: http://dmu.ac.uk

 

Personal profile

Dr Raffaella Villa joined De Montfort University in 2019 as Reader in Environmental Engineering. Prior to that she worked at Cranfield, Stirling, Exeter and the University of Milan (Italy).

Raffaella has worked on microbial bioengineering for the last 20 years. Her major contributions relate to the delivery of the next generation biotechnological processes that combine protection and production for a more circular bioeconomy, such as bioremediation and high-value products from waste. This is achieved by understanding the common science in the two areas (protection and production) on how to control and enhance specific functions of microbial communities by manipulating operative conditions to increase process yields and stability, with increasing emphasis on the concept of the “waste biorefinery”.

Raffaella has published over 60 research papers, books and conference proceedings with substantive contributions to waste biotransformations, bioremediation and anaerobic digestion.

Research group affiliations

Institute of Energy and Sustainable Development (IESD)

Publications and outputs 

  • Characterisation of food service establishment wastewater and its implication for treatment
    Characterisation of food service establishment wastewater and its implication for treatment Gurd, Caroline; Villa, R.; Jefferson, B. Essential for the selection of a reliable treatment system is the characterisation of the effluent to treat. Kitchen wastewater (KWW) from food service establishments (FSEs) is a strong organic and fat-rich effluent whose characterisation has not been sufficiently addressed. KWW composition is highly variable and linked to the FSE’s size, the type of meals prepared and the amount of water used during the cleaning. COD, TSS and fat content (FOG) are the most common parameters found in literature. However, other physical and chemical parameters (e.g. temperature, pH, oil droplets characteristics and trace elements), correlated to commercial kitchen cleaning practices rather than the specific effluent, but equally influential on the treatment efficiencies of both physical and biological methods, have hardly been investigated. A comprehensive characterisation of wastewaters from three food service establishments was used to generate data to support the selection of appropriate FOG mitigation methods. Two novel analytical methods were used to quantify the proportion of emulsified FOG and associated droplet size from different kitchen washing effluents. The results showed that more than 90% of the FOG from the dishwasher effluent and around 35% of sink one was emulsified, with droplet sizes less than 100 μm, well below the removal capabilities of conventional grease interceptors, but easily removed using biological means. From the WW composition results, a formula for predictive modelling was derived to represent average organic matter composition for kitchen wastewater as C20H38O10N, applicable in remediation processes. These results offer a good starting point for the design, operation, and optimisation of wastewater treatment systems of oil-rich KWW. The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.
  • Influence of light regime on the performance of an immobilised microalgae reactor for wastewater nutrient removal
    Influence of light regime on the performance of an immobilised microalgae reactor for wastewater nutrient removal Whitton, Rachel; Ometto, Francesco; Pidou, Marc; Jefferson, Bruce; Villa, R. Microalgae immobilised within a resin shaped into beads have demonstrated the ability to remediate nutrients from wastewater effluents within hydraulic retention times as low as 3 h. Methods to further optimise performance consider parameters relating to the bead with the impact of external conditions seldom investigated. Light is an essential parameter for microalgal growth with its effect on suspended cultures well documented. This work explores the influence of light on nutrient remediation by immobilised microalgae in order to recommend an optimal lighting solution for an immobilised microalgae technology based on Scenedesmus obliquus encapsulated within calcium-alginate beads. White light (400–700 nm) at a photon flux density (PFD) of 200 μmol∙m−2∙s−1 was determined optimal when illuminating a packed bed configuration. When considering phosphate, these conditions supported a remediation rate of 10.7 (± 0.01) mgP∙h−1∙106 beads−1 in comparison to 10.2 (± 0.01) and 10.1 (± 0.01) mgP∙h−1∙106 beads−1 for the blue (465 nm) and red (660 nm) spectra respectively. Although similar performance was demonstrated, light transmission trials determined white light to penetrate to greater bed depths resulting in a larger photoactive zone. A PFD of 200 μmol∙m−2∙s−1 was regarded as optimal when considering performance, attenuation depth and effective use of total supplied light. In addition, photoperiods trials determined lighting periods <12 h extended the overall treatment time. The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.
  • Liquid-phase hydrogenation of bio-refined succinic acid to 1,4-butanediol using bimetallic catalysts
    Liquid-phase hydrogenation of bio-refined succinic acid to 1,4-butanediol using bimetallic catalysts Baidya, P.K.; Sarkar, U.; Sadhukhan, S.; Villa, R. Development of a Crotalaria juncea based biorefinery produce large quantity of waste glycerol after trans-esterification of the juncea seeds. This glycerol, after purification, is used as a substrate for producing succinic acid on a microbial route. Hydrogenation of this bio-refined succinic acid is carried out under high pressure in order to produce 1,4- butanediol (BDO) using a batch slurry reactor with cobalt supported ruthenium bimetallic catalysts, synthesized inhouse. It is demonstrated that, using small amounts of ruthenium to cobalt increases the overall hydrogenation activity for the production of 1,4-butanediol. Hydrogenation reactions are carried out at various operating temperatures and pressures along with changes in the mixing ratios of ruthenium chloride and cobalt chloride hexahydrate, which are used to synthesize the catalyst. The Ru-Co bimetallic catalysts are characterized by XRD, FE-SEM and TGA. Concentrations of the hydrogenation product are analyzed using Gas chromatography-Mass spectrometry (GC-MS). Statistical analysis of the overall hydrogenation process is performed using a Box-Behnken Design (BBD). open access article
  • Determination of fats, oils and greases in food service establishment wastewater using a modification of the Gerber method
    Determination of fats, oils and greases in food service establishment wastewater using a modification of the Gerber method Gurd, C.; Jefferson, B.; De Castro Rodriguez, C.; Villa, R. Discharges from food service establishments (FSEs) are a major source of fat, oil and grease (FOG) which cause blockages in sewer networks. Previous research has identified that current methods are unsuitable for quantifying FOG in FSE wastewater owing to interference from surfactants in detergents, and protein from food residuals which emulsify FOG. A novel quantification method, based on the dairy industry Gerber method, has been developed which negates the impact of surfactants. Moreover, the method allows free and emulsified oil to be quantified separately providing greater insight into FOG management strategies. Trials in synthetic and real FSE wastewaters indicate the novel method is more reliable than standard liquid–liquid and solid phase extraction in FOG‐rich systems. open access article
  • From full-scale biofilters to bioreactors: engineering biological metaldehyde removal
    From full-scale biofilters to bioreactors: engineering biological metaldehyde removal Rolph, Catherine A.; Jefferson, Bruce; Brookes, Adam; Choya, Andoni; Iceton, Gregg; Hassard, Francis; Villa, R. Polar, low molecular weight pesticides such as metaldehyde are challenging and costly to remove from drinking water using conventional treatment methods. Although biological treatments can be effective at treating micropollutants, through biodegradation and sorption processes, only some operational biofilters have shown the ability to remove metaldehyde. As sorption plays a minor role for such polar organic micropollutants, biodegradation is therefore likely to be the main removal pathway. Here, the biodegradation of metaldehyde was monitored, and assessed, in an operational slow sand filter. Long-term data showed that metaldehyde degradation improved when inlet concentrations increased. A comparison of inactive and active sand batch reactors showed that metaldehyde removal happened mainly through biodegradation and that the removal rates were greater after the biofilm was acclimated through exposure to high metaldehyde concentrations. This suggested that metaldehyde removal was reliant on enrichment and that the process could be engineered to decrease treatment times (from days to hours). Through-flow experiments using fluidised bed reactors, showed the same behaviour following metaldehyde acclimation. A 40% increase in metaldehyde removal was observed in acclimated compared with non-acclimated columns. This increase was sustained for more than 40 days, achieving an average of 80% removal and compliance (< 0.1 µ L-1) for more than 20 days. An initial microbial analysis of the acclimated and non-acclimated biofilm from the same filter materials, showed that the microbial community in acclimated sand was significantly different. This work presents a novel conceptual template for a faster, chemical free, low cost, biological treatment of metaldehyde and other polar pollutants in drinking water. In addition, this is the first study to report kinetics of metaldehyde degradation in an active microbial biofilm at a WTW. The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.
  • On the potential of on-line free-surface constructed wetlands for attenuating pesticide losses from agricultural land to surface waters
    On the potential of on-line free-surface constructed wetlands for attenuating pesticide losses from agricultural land to surface waters Guymer, I.; Villa, R.; Jefferson, B.; Ramos, A.; Whelan, M. J. Pesticides make important contributions to agriculture but losses from land to water can present problems for environmental management, particularly in catchments where surface waters are abstracted for drinking water. “On-line” constructed wetlands have been proposed as a potential means of reducing pesticide fluxes in drainage ditches and headwater streams. Here, we evaluate the potential of two free-surface constructed wetland systems to reduce pesticide concentrations in surface waters using a combination of field monitoring and dynamic fugacity modelling. We specifically focus on metaldehyde, a commonly-used molluscicide which is moderately mobile and has been regularly detected at high concentrations in drinking water supply catchments in the UK over the past few years. We also present data for the herbicide metazachlor. Metaldehyde losses from the upstream catchment were significant with peak concentrations occurring in the first storm events in early autumn, soon after application. Concentrations and loads appeared to be minimally affected by transit through the monitored wetlands over a range of flow conditions. This was probably due to short solute residence times (quantified via several tracing experiments employing rhodamine WT – a fluorescent dye) exacerbated by solute exclusion phenomena resulting from patchy vegetation. Model analyses of different scenarios suggested that, even for pesticides with a relatively short aquatic half-life, wetland systems would need to exhibit much longer residence times (RTs) than those studied here in order to deliver any appreciable attenuation. If the ratio of wetland surface area to the area of the contributing catchment is assumed to be a surrogate for RT (i.e. not accounting for solute exclusion) then model predictions suggest that this needs to be greater than 1% to yield load reductions of 3 and 7% for metaldehyde and metazachlor, respectively. The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.
  • Tertiary nutrient removal from wastewater by immobilised microalgae: impact of wastewater nutrient characteristics and hydraulic retention time (HRT)
    Tertiary nutrient removal from wastewater by immobilised microalgae: impact of wastewater nutrient characteristics and hydraulic retention time (HRT) Whitton, R.; Pidou, M.; Ometto, F.; Henderson, R.; Roddick, F.; Jarvis, P.; Jefferson, B.; Villa, R.; Santinelli, M. Immobilising microalgal cells has been proposed as a process solution to overcome the barriers associated with the implementation of microalgae for wastewater remediation. This work evaluated the performance and remediation mechanisms of immobilised microalgae for continuous wastewater treatment under varying hydraulic retention times (HRT). Three domestic secondary wastewaters with differing concentrations of orthophosphate (PO4-P), ammonium (NH4-N) and nitrate (NO3-N) were treated by Scenedesmus obliquus immobilised within 2% calcium alginate. Trials were run in continuous operation at HRTs of 3, 6, 12 and 20 h. Removal rates for PO4-P improved with increasing HRT, with minimum residual concentrations of 0.3–3.1 mg·L−1 observed at 3 h and 0.01–0.2 mg·L−1 at 20 h. Ammonium remediation was not linked to HRT or NH4+ concentration with minimum residual concentrations of <0.001 mg·L−1. Reduction in NO3-N improved with increasing HRT, with minimum residual concentrations of ≤19.3 at 3 h and ≤0.4 mg·L−1 at 20 h. Remediation was achieved through a combination of mechanisms including biological uptake and precipitation as a by-product of photosynthesis and nutrient metabolism. As such, immobilised microalgae have been proven to be an effective alternative solution for PO43− and NH4+ remediation of wastewater effluents at HRTs of 6–12 h. open access article
  • Risk assessments for quality-assured, source-segregated composts and anaerobic digestates for a circular bioeconomy in the UK
    Risk assessments for quality-assured, source-segregated composts and anaerobic digestates for a circular bioeconomy in the UK Longhurst, P.J.; Tompkins, D.; Pollard, S.J.T.; Hough, R.L.; Chambers, B.; Gale, P.; Tyrrel, S.; Taylor, M.; Wu, S.; Sakrabani, R.; Litterick, A.; Snary, E.; Sweet, N.; Leinster, P.; Villa, R. A circular economy relies on demonstrating the quality and environmental safety of wastes that are recovered and reused as products. Policy-level risk assessments, using generalised exposure scenarios, and informed by stakeholder communities have been used to appraise the acceptability of necessary changes to legislation, allowing wastes to be valued, reused and marketed. Through an extensive risk assessment exercise, summarised in this paper, we explore the burden of proof required to offer safety assurance to consumer and brand-sensitive food sectors in light of attempts to declassify, as wastes, quality-assured, source-segregated compost and anaerobic digestate products in the United Kingdom. We report the residual microbiological and chemical risks estimated for both products in land application scenarios and discuss these in the context of an emerging UK bioeconomy worth £52bn per annum. Using plausible worst case assumptions, as demanded by the quality food sector, risk estimates and hazard quotients were estimated to be low or negligible. For example, the human health risk of E. coli 0157 illness from exposure to microbial residuals in quality-assured composts, through a ready-to-eat vegetable consumption exposure route, was estimated at ~10−8 per person per annum. For anaerobic digestion residues, 7 × 10−3 cases of E. coli 0157 were estimated per annum, a potential contribution of 0.0007% of total UK cases. Hazard quotients for potential chemical contaminants in both products were insufficient in magnitude to merit detailed quantitative risk assessments. Stakeholder engagement and expert review was also a substantive feature of this study. We conclude that quality-assured, source-segregated products applied to land, under UK quality protocols and waste processing standards, pose negligible risks to human, animal, environmental and crop receptors, providing that risk management controls set within the standards and protocols are adhered to. open access article

Research interests/expertise

Dr. Villa's research interests include:

applied microbial processes across the fields of wastewater treatment (bioremediation) and energy from waste (anaerobic digestion and algae);

waste biotransformation;

environmental engineering.

Qualifications

PGCert in Academic Practice

PhD in Food Biotechnologies, Universitá di Milano (Italy)

BSc and MSc in Food Sciences and Technologies, Universitá di Milano (Italy)

Honours and awards

Personal Marie Curie Post-Doctoral Fellowship (EU FP5), Stirling University 2000

MIUR (Ministry of Education, Universities and Research) Personal Advancement Fellowship (1995)

Membership of external committees

Member of the Editorial Board of ICE Water Management (https://www.icevirtuallibrary.com/toc/jwama/current)

Editor in Chief of Environmental Technology Reviews (https://www.tandfonline.com/toc/tetr20/current)

Membership of professional associations and societies

Member of the Society for Applied Microbiology

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