Browsing by Author "Colston, Robert"
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Item Open Access Enhanced bio-minerals production using catalysts to accelerate resource recovery in wastewater treatment plants.(Cranfield University, 2023-01) Colston, Robert; Soares, Ana; Stephenson, TomThe biomineralisation mechanisms of five known bio-struvite producing microbes have been established and their ability to recover said biomineral from synthetic solutions and sludge dewatering liquors has been trialled. There is a lack of evidence and knowledge how these microbes perform in open culture conditions and the impact encapsulating media has on their ability to remove and recover orthophosphate as bio-struvite. In this PhD thesis, these microorganisms (Brevibacterium antiquum, Bacillus pumilus, Halobacterium salinarum, Idiomarina loihiensis, Myxococus xanthus) were investigated initially, this was streamlined into investigating encapsulated cultures of B. antiquum and B. pumilus in wastewaters under open culture conditions. The inoculation of all five microbes in source-separated urine in open culture conditions showed growth rates as high as 0.18 1/h and high nucleic acid proportions >80% within 24 hours of incubation. An orthophosphate removal of up to 70% was achieved by B. antiquum inoculations and was increased to 100% when magnesium was increased to a 1:1, P:Mg. Encapsulated cultures of B. pumilus were incubated B4.1 growth media, the removal of orthophosphate and chemical oxygen demand was equal to suspended cell inoculations of B. pumilus. In pure culture and open culture sludge dewatering liquors, encapsulated cultures of B. pumilus and B. antiquum, removed 55% and 70% of the initial orthophosphate over 24 hours respectively. The minimal difference in orthophosphate removal between pure and open culture conditions indicates that encapsulation provided an environmental advantage to the selected microbes to out compete the native species within the open culture sludge dewatering liquors. Suspended cell inoculations into open culture sludge dewatering liquors did not remove any more orthophosphate than non-inoculated controls. In continuous reactors fed by open culture sludge dewatering liquors orthophosphate removal for both encapsulated microbes averaged between 20% and 30%, at phosphorus loading rates of 0.4 kg P/m³ .d and 0.6 kg P/m³ .d. Supplementing a carbon source to the equivalent of 150 mg sCOD/L and increasing the ratio of P:Mg to 1:1.5, achieved an orthophosphate removal of 96% on average by encapsulated B. antiquum. Bio-struvite recovered from all open culture wastewaters was euhedral, prismatic and tabular and was typically coated in a secondary abiotic calcium phosphate. Micropollutant analysis showed the recovered minerals were below international heavy metal limits and were absent from faecal coliforms, pharmaceuticals and other micropollutants for fertilisers. Potential end users and consumers from the public and industry showed a strong willingness to use and eat produce grown from recycling derived fertilisers. There remains to be optimisation of the biomineralisation technique to improve the efficiency of recovery and streamline the operational set up, however the data collected in this PhD strongly supports the development of this technique into industry and will satisfy a growing need for circular economies and closing the nutrient loop.Item Open Access Predicting the potential of sludge dewatering liquors to recover nutrients as struvite biominerals(Elsevier, 2020-06-27) Simoes, Francisco; Colston, Robert; Rosa-Fernandes, Catarina; Vale, Peter; Stephenson, Tom; Soares, AnaPhosphorus and nutrient recovery from wastewater as mineral salts can support local replenishment of fertilisers and reduce mining, contributing to the circular economy. Wastewater and related streams are rich in nutrients, however; there is need to develop bio-based processes to recover them. This study investigates the fractions of phosphorus (P) used by Brevibacterium antiquum to form struvite biominerals (bio-struvite) in wastewater sludge dewatering liquors. After 72h of incubation, 25.6 mg P/L were recovered as bio-struvite from 12.4 mg P/L organic plus condensed P and 13.2 mg P/L of ortho-phosphate. The potential of sludge dewatering liquors to recover nutrients as struvite was investigated by characterising ten types of sludge liquors (originating from primary, secondary sludge, feed to anaerobic digester and digestate, from 3 types of wastewater treatment plants) for their P fractions together with other parameters relevant for B. antiquum growth. Results indicated that liquors obtained from primary sludge, feed to anaerobic digesters and digestate were the most suitable to produce bio-struvite, as these were found to frequently have a high content of organic and condensed P, between to 276–732 mg P/L. Liquors, from all the investigated sites, presented a higher potential for bio-struvite production than with conventional struvite precipitation. This study demonstrated that B. antiquum could convert organic and condensed P into bio-struvite, and this opens up a completely new way to recover forms of phosphorus that are not typically available for nutrient recovery in a single processItem Open Access Understanding the biochemical characteristics of struvite bio-mineralising microorganisms and their future in nutrient recovery(Elsevier, 2020-01-08) Leng, Yirong; Colston, Robert; Soares, AnaThe biochemical properties of selected microorganisms (Bacillus pumilus, Brevibacterium antiquum, Myxococcus xanthus, Halobacterium salinarum and Idiomarina loihiensis), known for their ability to produce struvite through biomineralisation, were investigated. All five microorganisms grew at mesophilic temperature ranges (22–34 °C), produced urease (except I. loihiensis) and used bovine serum albumin as a carbon source. I. loihiensis was characterised as a facultative anaerobe able to use O2 and NO3 as an electron acceptor. A growth rate of 0.15 1/h was estimated for I. loihiensis at pH 8.0 and NaCl 3.5% w/v. The growth rates for the other microorganisms tested were 0.14–0.43 1/h at pH 7–7.3 and NaCl ≤1% w/v. All the microorganisms produced struvite, as identified by morphological and X-ray Powder Diffraction (XRD) analysis, under aerobic conditions. The biological struvite yield was between 1.5 and 1.7 g/L of media, the ortho-phosphate removal and recovery were 55–76% and 46–54%, respectively, the Mg2+ removal and recovery was 92–98% and 83–95%, respectively. Large crystals (>300 μm) were observed, with coffin-lid and long-bar shapes being the dominant morphology of biological struvite crystals. The characterisation of the biochemical properties of the studied microorganisms is critical for reactor and process design, as well as operational conditions, to promote phosphorus recovery from waste streams.