Browsing by Author "Murujew, Olga"

Now showing 1 - 4 of 4
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    The impact of polymer selection and dose on the incorporation of ballasting agents onto wastewater aggregates
    (Elsevier, 2019-11-28) Murujew, Olga; Geoffroy, Jordan; Fournie, Emeline; Gioacchini, Elisa Socionovo; Wilson, Andrea; Vale, Peter C. J.; Jefferson, Bruce; Pidou, Marc
    Ballasted flocculation is an efficient high-rate sedimentation process getting more attention as an advanced P removal technology for levels below 0.1 mg/L. The process is well-known yet only very few studies have investigated the interactions, within the matrix of wastewater, of coagulant, polymer and ballast, especially when it comes to polymer doses and types which are, in the industry, rather based on recommendations than scientific evidence. In this work, the impact of anionic and cationic polymers has been investigated on P removal and floc properties. Anionic polymers showed to be superior to cationic ones when it comes to P removal and doses even as low as 0.01 mg/L yield better results than coagulant alone. There appears to be a “best-case” floc size with which very good P removal (>90%) can be achieved and flocs of sufficient strength can be generated.
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    Reactive media constructed wetland for phosphorus removal: assessing the opportunity and challenges
    (IWA Publishing, 2024-03-09) Murujew, Olga; Le Corre, Kristell; Wilson, Andrea; Bajón Fernández, Yadira; Vale, Peter C. J.; Jefferson, Bruce; Pidou, Marc
    Reactive media present an alternative to gravel in constructed wetlands and have the potential to sustainably and efficiently remove phosphorus from wastewater. In this study, a full-scale steel slag wetland has been operated for its whole lifecycle at which 1.39 mg P/g media were retained. During its lifecycle, this wetland met strict consents below 0.5 mg P/L for the first 6 months and was operated for 266 and 353 days before the effluent phosphorus concentration rose above the typical consents of 1 and 2 mg P/L, respectively. A detailed analysis of the system demonstrated that the performance was directly associated with the release of materials from the media into the water which in turn affected other critical parameters such as pH. Further analysis of the media suggested that greater understanding was needed concerning the role of carbonates and in particular calcite if steel slag is to be effectively managed for use on constructed wetlands. Importantly, controlled release of calcium oxide from the media surface is required by managing the concerns of pH and vanadium release.
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    Recovery and reuse of alginate in an immobilised algae reactor
    (Taylor and Francis, 2019-09-27) Murujew, Olga; Whitton, Rachel; Kube, Matthew; Fan, Linhua; Roddick, Felicity; Jefferson, Bruce; Pidou, Marc
    The use of microalgae for nutrients removal from wastewater has attracted more attention in recent years. More specifically, immobilized systems where algae cells are entrapped in beads in a matrix of a polysaccharide such as alginate have shown a great potential for nutrients removal from wastewater to low levels with reduced retention times and hence smaller footprint. However, a significant operational cost in the up-scaling of alginate-immobilized algae reactors will be the gelling agent alginate. To reduce expenditure of this consumable a proof-of-concept is given for an alginate recycling method using sodium citrate as a dissolving agent. Using algae beads made from virgin and recycled alginate yielded comparable removal rates for both phosphorus and nitrogen compounds from wastewater. At labscale, an alginate recovery of approximately 70% can be achieved which would result in a net operational cost reduction of about 60%.
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    Tertiary phosphorus removal from wastewater.
    (Cranfield University, 2019-04) Murujew, Olga; Pidou, Marc; Jefferson, Bruce
    To protect surface water bodies, final effluents of wastewater treatment works are being regulated with stricter consents. Phosphorus has been identified as a priority compound and according to the Water Framework Directive its levels in wastewater effluents need to be below 1 mg P/L and in some cases as low as 0.1 mg P/L. To meet these consents efficiently and economically, there are several novel or established tertiary P removal technologies. Chemical P removal is a conventionally applied process. Yet, it requires optimisation in chemical doses and the most appropriate solids liquid separation for tertiary P removal needs yet to be identified to meet the new stricter consents sustainably. Novel tertiary P removal technologies such as immobilised algae beads systems or reactive media constructed wetlands provide a more sustainable approach with no direct use of chemicals on site and the recycling of materials such as the media in the wetland or through conversion of the algal biomass to energy. However, these technologies are not yet fully established and require validation of their viability and cost competitiveness. In this thesis, tertiary P removal technologies have been evaluated with the aim to resolve existing bottlenecks that are associated with the implementation of these technologies when meeting sub 1 mg P/L levels. Three coagulation-based technologies that have not been operated previously in the UK were assessed on their robustness and resilience under steady-state and dynamic conditions against a 0.3 mg P/L target. It was found that ballasted coagulation was the most robust and could consistently deliver effluent concentrations as low as 0.1 mg P/L. Pile cloth media filtration and ultrafiltration were shown to be less robust yet effective at reaching 0.3 and 0.5 mg P/L targets, respectively. The importance of the solid liquid separation step as well as optimisation of dosing and coagulation- flocculation was highlighted. Further it was found that in a ballasted coagulation system, weaker and bigger flocs are generated through the addition of polymer which are efficiently separated through the incorporation of a ballasting agent. Ultimately, guidance on suitable choice of polymers and their doses was given as anionic polymers at doses as low as 0.1 mg/L. From the novel alternatives, a reactive media (steel slag) constructed wetland was operated at full-scale under real conditions and has reached the highest reported P retention capacity to date with very low P effluent concentrations (<1 mg/L from an average of about 8 mg/L) achieved in the first year of operation. During the life cycle of the wetland, P removal decreased substantially, and it was highlighted that the underlying mechanisms are more complex than previously assumed. To address the bottleneck of high costs of beads production in immobilised algae systems, a proof-of-concept has been given where 69.1% alginate recovery was achieved, and algae beads made from recycled alginate were further reused in P removal trials. Ultimately, a cost reduction of 34% of operational costs could be achieved. Finally, the insights were translated into a P removal strategy where the most suitable technologies are recommended for differently scaled wastewater treatment works (WWTW) and different effluent P targets based on their performance, costs and sustainability. For large WWTW, ballasted coagulation appeared to be the most suitable technology while for small WWTW pile cloth media filtration is recommended. Based on this research, ultrafiltration cannot be recommended for tertiary P removal. The novel technologies were highlighted as more sustainable options for small WWTW which still need further understanding and development.