Browsing by Author "Raper, Eleanor"
Now showing 1 - 6 of 6
Results Per Page
Sort Options
Item Open Access Biological treatment of coke making wastewater.(2017-04) Raper, Eleanor; Soares, Ana; Stephenson, TomProduction of coke for steel manufacturing produces a wastewater containing total nitrogen (TN) (up to 600 mg/L) alongside toxic compounds phenol (60 - 400 mg/L), thiocyanate (SCN-) (100 - 400 mg/L), polycyclic aromatic hydrocarbons (PAHs) (Ʃ6PAHs:179±35 µg/L) and trace metals. Emission limits introduced by the Industrial Emissions Directive (IED) in 2016 require treated coke effluent to contain <50 mg/L TN, <4 mg/L SCN-, <0.5 mg/L phenol and <50 µg/L Ʃ6PAHs which cannot be consistently met by the conventional activated sludge process (ASP). Treatment process modifications were investigated to ensure compliance. Activated carbon addition to the ASP (400 mg/L) increased Ʃ6PAHs removal by 20% enabling emission compliance whilst increasing nickel, chromium and cadmium removal. The addition of 0.5 g/L of a commercial bioaugmentation product increased dissolved Ʃ6PAHs removal by 51%. Biostimulation (addition of micronutrients/alkalinity) enabled SCN-and phenol emission compliance. Survival of supplemented exogenous bacteria in a simulated river water discharge was investigated for the first time showing limited survivability. Thiocyanate degradation mechanisms were poorly understood but were important to ascertain, especially as SCN-degradation produces ammonia increasing TN loading. Control of influent ammonia and phenol concentration was important enabling SCN-degradation under anoxic and aerobic conditions. Deoxyribonucleic acid sequencing of the mixed culture identified a new species of Thiobacillus which had metabolic similarities to T. thioparus and T. denitrificans. Nitrification was limited (41%) confirming the importance of intrinsic alkalinity availability in the wastewater, however, sodium carbonate addition (300 mg/L as CaCO₃) increased efficiencies to 96%. An anoxic-aerobic ASP was investigated for TN removal enabling an effluent TN <50 mg/L when the soluble chemical oxygen demand (sCOD):TN ratio was maintained above 5.7. Acetic acid was identified as a suitable source of carbon addition to maintain this ratio. An anoxic-aerobic ASP combined with AC and bioaugmentation can ensure compliance with the IED.Item Open Access Characterisation of thiocyanate degradation in a mixed culture activated sludge process treating coke wastewater(Elsevier, 2019-05-22) Raper, Eleanor; Stephenson, Tom; Fisher, Raymond; Anderson, David R.; Soares, AnaMicrobial degradation of thiocyanate (SCN−) has been reported to suffer from instability highlighting the need for improved understanding of underlying mechanisms and boundaries. Respirometry, batch tests and DNA sequencing analysis were used to improve understanding of a mixed culture treating coke wastewater rich in SCN−. An uncultured species of Thiobacillus was the most abundant species (26%) and displayed similar metabolic capabilities to Thiobacillus denitrificans and Thiobacillus thioparus. Thiocyanate was hydrolysed/oxidised to NH4+-N, HCO3− and SO42−. Nevertheless, at 360–2100 mg SCN−/L a breakdown in the degradation pathway was observed. Respirometry tests demonstrated that NH4+-N was inhibitory to SCN− degradation (IC50: 316 mg/L). Likewise, phenol (180 mg/L) and hydroxylamine (0.25–16 mg/L) reduced SCN− degradation by 41% and ca. 7%, respectively. The understanding of the SCN− degradation pathways can enable stable treatment efficiencies and compliance with effluent of <4 mg SCN/L, required by the Industrial Emissions Directive.Item Open Access Enhancing the removal of hazardous pollutants from coke making wastewater by dosing activated carbon to a pilot‐scale activated sludge process(Wiley: 12 months, 2017-02-09) Raper, Eleanor; Soares, Ana; Chen, J.; Sutcliffe, A.; Aries, E.; Anderson, D.; Stephenson, TomPowdered activated carbon (PAC) was investigated for its ability to remove 6 polycyclic aromatic hydrocarbons (Σ6PAHs) (fluoranthene, benzo[b + J]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, benzo[g,h,i]perylene), trace metals and colour from coke making wastewater when dosed to a pilot-plant activated sludge process (ASP). The ASP had a volume of 0.68 m3 and was operated to simulate the full-scale ASP treating coke wastewater from a steel works. Operational conditions included a flow rate of 0.78 m3/day, a hydraulic retention time of 21 hours, a sludge retention time of 38 days and a temperature of 27°C. The ASP was operated for a control period before PAC was dosed directly into the aeration cell at a dose of 400 mg/L. Powdered activated carbon addition resulted in a 20% increase in removal efficiency of the Σ6PAHs. Removal efficiency of trace metals was variable, but increased for nickel, chromium and cadmium by 22.6%, 20.5% and 12.4%, respectively. Improvement in colour removal efficiency was marginal at 5%. PAC addition allowed the improvement of treatment efficiencies in the ASP process at relatively low capital and operational costs, which may assist in reaching tighter effluent emission limits set for the industry.Item Open Access Enhancing the removal of pollutants from coke wastewater by bioaugmentation: a scoping study(2018-02-09) Raper, Eleanor; Stephenson, Tom; Simões, Francisco; Fisher, Raymond; Anderson, David R.; Soares, AnaBACKGROUND Bioaugmentation and biostimulation were investigated for their ability to improve the removal of thiocyanate (SCN-), polycyclic aromatic hydrocarbons (PAHs), phenol and trace metals in coke wastewater. Additionally, the ability of the microorganisms supplemented with the bioaugmentation product to survive in a simulated river water discharge was evaluated. RESULTS A commercially available bioaugmentation product composed mainly of Bacillus sp. was mixed with activated sludge biomass. A dose of 0.5 g/L increased the removal of Ʃ6PAHs (sum of fluoranthene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene and benzo[g,h,i]perylene) by 51% and reduced SCN- below 4 mg/L enabling compliance with the EU Industrial Emissions Directive (IED). Biostimulation (supplementing micronutrients and alkalinity) allowed compliance for both SCN- and phenol (<0.5 mg/L). Bacillus sp. accounted for 4.4% of the microbial population after 25 hours (1.5 g/L dose) which declined to 0.06% after exposure to river water (24 hours). Exposure of the activated sludge biomass to river water resulted in a 98.6% decline in viable cell counts. CONCLUSION To comply with the IED, bioaugmentation and biostimulation are recommended for the treatment of coke wastewater to enable an effluent Ʃ6PAHs of 6.6 μg/L, 0.3 mg/L phenol and 1.2 mg/L SCN-. Such techniques are not anticipated to impact on downstream river water quality.Item Open Access Industrial wastewater treatment through bioaugmentation(Elsevier, 2018-06-28) Raper, Eleanor; Stephenson, Tom; Anderson, D. R.; Fisher, R.; Soares, AnaBioaugmentation of activated sludge processes through the addition of microorganisms is employed with the aim of enhancing treatment, in particular the removal of priority pollutants. With industrial wastewaters, studies have covered target pollutants including ammonia and polycyclic aromatic hydrocarbons (PAHs): compounds that are regulated around the globe. However, bioaugmentation is a technique that has been associated with doubt in regard to its ability to benefit treatment processes. Failure of bioaugmentation has been reported to be associated with numerous factors that include the growth rate being lower than the rate of washout, insufficient inoculum size and substrate availability. Limitations of bioaugmentation can be overcome through techniques that include increased inocula dosing, pre-acclimatisation of inocula in side-stream reactors, addition of nutrients and surfactants and application of sufficient acclimatisation periods. Surveys of the literature show that a key area for further research should be towards acquiring a better understanding of the degradation pathways where bioaugmentation is applied. There also remains a need to undertake bioaugmentation efficacy studies at full scale with test and control streams. Further reporting on the economic viability of the technique is also necessary.Item Open Access Nitrogen removal from coke making wastewater through a pre-denitrification activated sludge process(Elsevier, 2019-02-14) Raper, Eleanor; Fisher, R.; Anderson, D. R.; Stephenson, Tom; Soares, AnaUnder the Industrial Emissions Directive (IED), coke production wastewater must be treated to produce an effluent characterised by a total nitrogen (TN) <50 mg/L. An anoxic-aerobic activated sludge pilot-plant (1 m3) fed with coke production wastewater was used to investigate the optimal operational requirements to achieve such an effluent. The loading rates applied to the pilot-plant varied between 0.198–0.418 kg COD/m3.day and 0.029–0.081 kg TN/m3.day, respectively. The ammonia (NH4+-N) removals were maintained at 96%, after alkalinity addition. Under all conditions, phenol and SCN− remained stable at 96% and 100%, respectively with both being utilised as carbon sources during denitrification. The obtained results showed that influent soluble chemical oxygen demand (sCOD) to TN ratio of should be maintained at >5.7 to produce an effluent TN <50 mg/L. Furthermore, nitrite accumulation was observed under all conditions indicating a disturbance to the denitrification pathway. Overall, the anoxic-aerobic activated sludge process was shown to be a robust and reliable technology to treat coke making wastewater and achieve the IED requirements. Nevertheless, the influent to the anoxic tank should be monitored to ensure a sCOD:TN ratio >5.7 or, alternately, the addition of an external carbon source should be considered.