Publications
63 results found
Koulouri ME, Templeton MR, Fowler GD, 2024, Enhancing the nitrogen and phosphorus content of faecal-derived biochar via adsorption and precipitation from human urine, Journal of Environmental Management, Vol: 352, ISSN: 0301-4797
Urine diversion in toilets is a promising strategy to maximise nutrient recovery and produce low-cost urine-derived fertilisers. There are various methods for nutrient recovery from urine, including precipitation and adsorption onto porous media, such as biochars. This study uses faecal-derived biochars to produce and, for the first time, comprehensively characterise enriched biochar fertilisers with the addition of fully hydrolysed undiluted human urine. The evolution of urea hydrolysis and nutrient content during urine storage was initially investigated over a 6-month storage period and NH4+ adsorption mechanisms studied under varying biochar doses and NH4–N concentrations. The process was further optimised by adding MgO to induce precipitation reactions, enabling the combined recovery of NH4+ and P. For NH4+ adsorption, experimental data exhibited a good fit to both the Freundlich (R2 = 0.989) and Langmuir (R2 = 0.974) isotherm models and the rate of the reaction was well described by a pseudo 2nd order kinetics model (R2 = 0.988). The NH4+ uptake was rapid during the initial 2 h of the reaction and the adsorption process reached completion after 24 h. The NH4–N adsorption capacity of the faecal-derived biochar was 19.8 mg/g and the main adsorption mechanism identified was ion exchange (K+ ↔ NH4+), as confirmed by XRD and ICP-OES. The effect of different biochar doses (0, 25, 50, 100 g/L) and MgO addition scenarios (Mg:P = 0, 1.5, 4) on N and P recovery showed that the combination of MgO (Mg:P = 1.5) with the lower biochar dose (25 g/L) produced the most NP-rich fertiliser product which was easily separated from the urine. Faecal-derived biochar had a limited adsorption capacity for P, with precipitation being the main mechanism for P recovery. When MgO was added to urine, >98% of total P was recovered via precipitation of struvite/struvite-K and substituted hydroxyapatite, as identified via SEM-EDX. Faecal-derived biochar was a successful car
Gomez M, Grimes S, Fowler G, 2023, Novel hydrometallurgical process for the recovery of copper from end-of-life mobile phone printed circuit boards using ionic liquids, Journal of Cleaner Production, Vol: 420, ISSN: 0959-6526
Printed circuit boards, which are embedded in mobile phones, are complex composite materials containing valuable components of strategic and critical importance. With the number of mobile phone devices operating worldwide expected to reach 18bn by 2025, their low recycling rate leads to high tonnages of waste printed circuit boards (WPCBs) at their end of life. Copper, representing 58% of the total metal content in an end-of-life mobile phone (EoL-MP) and the main metal present in the printed circuit board, with an average of 27.8 wt %, offers a resource-rich source of this strategic metal for recovery. To overcome the limitations associated with conventional technologies for recycling WPCBs, use of greener technologies (ionic liquids (ILs) as leaching agents), offers greater potential for the recovery of copper from this waste stream. Presented here for the first time is an optimised hydrometallurgical process for recovery of copper involving pre-treatment, leaching, and electrowinning and the use of two task-specific ionic liquids. The pre-treatment step, using the IL [Bmim]BF4 proved to be a clean, efficient, and non-polluting system for the separation of solder and electronic components (ECs) from WPCBs, at 210 °C, 150 rpm for 15 min, favouring the enrichment of copper for a subsequent recovery process. The IL, [Bmim]HSO4, successfully leaches >99% of copper from pretreated WPCBs under the optimal conditions of 30 %v/v [Bmim]HSO4, 10 %v/v H2O2, and 60 %v/v H2O at 60 °C, 1:15 solid to liquid ratio for 2 h. Recovery of copper is achieved through direct electrowinning from the [Bmim]HSO4-leach solution, as electrolyte. Under controlled deposition conditions of 100 mA (4.2 V) during 2 h, 100% of copper (>99% purity) is recovered with an average current efficiency of 78% and an energy consumption of 4.5 kWh/kg Cu. This work combines a dual leaching and electrowinning system that is clean, environmentally friendly, minimises reagent use and spent wastes
Koulouri ME, Templeton MR, Fowler GD, 2023, Source separation of human excreta: effect on resource recovery via pyrolysis, Journal of Environmental Management, Vol: 338, Pages: 1-10, ISSN: 0301-4797
More people globally are now using on-site sanitation technologies than sewered connections. The management of faecal sludge generated by on-site facilities is still challenging and requires an understanding of all sanitation service chain components and their interactions; from source conditions to treatment and resource recovery. This study aimed to improve the current lack of knowledge regarding these interactions, by establishing a quantifiable relationship between human excreta source separation and resource recovery via pyrolysis. The effects of source separation of faeces and urine on biochar quality were investigated for different pyrolysis temperatures (450 °C, 550 °C, 650 °C) and this information was used to assess energy and nutrient recovery. Results quantify the benefits of urine diversion for nitrogen recovery (70% of total N losses during thermal treatment avoided) and show an increase in the liming potential of the produced faecal-based biochars. The quality of produced solid fuels is also improved when source-separated faeces (SSF) are used as a feedstock for pyrolysis, including a 50% increase in char calorific value. On the other hand, biochars from mixed urine and faeces (MUF) are more rich in phosphorus and potassium, and surface morphology investigation indicates higher porosity compared to SSF biochars. The high salinity of MUF biochars should be considered before agricultural applications. For both biochar types (SSF, MUF), the presence of phosphate compounds of high fertiliser value was confirmed by X-ray diffraction analysis, and temperatures around 500 °C are recommended to optimise nutrient and carbon behaviour when pyrolysing human excreta. These findings can be used for the design of circular faecal sludge management systems, linking resource recovery objectives to source conditions, and vice-versa. Ultimately, achieving consistent resource recovery from human excreta can act as an incentive for universal access to safe
Bowles AJ, Nievas A, Fowler GD, 2023, Consecutive recovery of recovered carbon black and limonene from waste tyres by thermal pyrolysis in a rotary kiln, Sustainable Chemistry and Pharmacy, Vol: 32, ISSN: 2352-5541
End of life tyres are one of the most abundant and least recycled waste streams. Material recovery processes that accommodate for the complexity and heterogeneity of waste tyres, such as pyrolysis, require urgent development. Examples of recycled tyre pyrolysis products include recovered carbon black (RCb), a recycled filler, and limonene, a solvent, although investigations reporting the recovery of both are limited. In this study the pyrolysis of waste tyres was investigated in a batch rotary kiln under varying conditions (temperature, gas flow, sample mass). Characterisation analysis was then applied to selected samples of RCb (BET surface area, transmissibility of toluene extract, proximate analysis) and tyre pyrolysis oil (yield, limonene content, FTIR). The best RCb (77.7 m2/g, 0.2% volatile matter, 17.0% ash, 94.8% transmissibility of toluene extract) was produced at 550 °C with a high ratio of purge gas flow (2000 mL/min) to rubber sample mass pyrolysed (100 g), minimising the recondensation of tarry volatiles on the RCb. The highest oil and limonene yield (38.4% and 17.4 g/kg waste tyres respectively) was produced at a temperature of 550 °C with a low ratio of purge gas (400 mL/min) to rubber sample pyrolysed (200 g), as these conditions prevented the decomposition of limonene to less valuable products and improved the oil trap condensation efficiency. These findings demonstrate the importance of pyrolysis processing conditions when considering the consecutive production of RCb and solvents from waste tyre pyrolysis, which shows significant future potential to valorise waste tyres, incentivising recycling.
Bowles AJ, Fowler GD, 2022, Assessing the impacts of feedstock and process control on pyrolysis outputs for tyre recycling, Resources, Conservation and Recycling, Vol: 182, ISSN: 0921-3449
Tyres are a problematic waste stream which are associated with low recycling rates; most are dumped or incinerated, offering poor value return from this material-rich and energy intensive waste. Pyrolysis offers the potential for ~30% of a tyre to be directly recyclable as ‘recovered carbon black’ (RCb), potentiating tyre-to-tyre recycling. However, most attempts to exploit the process have failed to produce consistent, high quality RCb on a commercially viable scale. Current consensus implies that RCb quality can only be improved by expensive post-processing, such as demineralisation using chemical solvents. Here it is shown that the quality (ash and volatile matter content) and consistency of RCb can be improved significantly by careful application of feedstock and process control during pyrolysis. This was achieved via the analysis of peer reviewed data from 31 waste tyres and yields from 161 runs in 37 pyrolysis reactors. A statistical bootstrapping regime showed that by selective exclusion of high ash tyres, and mixing the remainder thoroughly, RCb ash content could be reduced from 49% (upper 99% CI) to 14%. By utilising a unique reactor classification, it was found that fixed beds performed inconsistently, whilst rotary kilns and conical spouted beds produced high quality RCb and a high oil yield, even at lower pyrolysis temperatures. Due to their higher throughput, this work therefore suggests that application of rotary kilns with feedstock control are the best mechanisms to produce consistent high-quality products from pyrolysis, increasing the recyclability of automotive tyres.
Krueger BC, Fowler GD, Templeton MR, et al., 2021, Faecal sludge pyrolysis: understanding the relationships between organic composition and thermal decomposition, Journal of Environmental Management, Vol: 298, Pages: 1-13, ISSN: 0301-4797
Sludge treatment is an integral part of faecal sludge management in non-sewered sanitation settings. Development of pyrolysis as a suitable sludge treatment method requires thorough knowledge about the properties and thermal decomposition mechanisms of the feedstock. This study aimed to improve the current lack of understanding concerning relevant sludge properties and their influence on the thermal decomposition characteristics. Major organic compounds (hemicellulose, cellulose, lignin, protein, oil and grease, other carbohydrates) were quantified in 30 faecal sludge samples taken from different sanitation technologies, providing the most comprehensive organic faecal sludge data set to date. This information was used to predict the sludge properties crucial to pyrolysis (calorific value, fixed carbon, volatile matter, carbon, hydrogen). Samples were then subjected to thermogravimetric analysis to delineate the influence of organic composition on thermal decomposition. Septic tanks showed lower median fractions of lignin (9.4%dwb) but higher oil and grease (10.7%dwb), compared with ventilated improved pit latrines (17.4%dwb and 4.6%dwb respectively) and urine diverting dry toilets (17.9%dwb and 4.7%dwb respectively). High fixed carbon fractions in lignin (45.1%dwb) and protein (18.8%dwb) suggested their importance for char formation, while oil and grease fully volatilised. For the first time, this study provided mechanistic insights into faecal sludge pyrolysis as a function of temperature and feedstock composition. Classification into the following three phases was proposed: decomposition of hemicellulose, cellulose, other carbohydrates, proteins and, partially, lignin (200–380 °C), continued decomposition of lignin and thermal cracking of oil and grease (380–500 °C) and continued carbonisation (>500 °C). The findings will facilitate the development and optimisation of faecal sludge pyrolysis, emphasising the importance of considering the
Larasati A, Fowler GD, Graham NJD, 2021, Extending granular activated carbon (GAC) bed life: A column study of in-situ chemical regeneration of pesticide loaded activated carbon for water treatment., Chemosphere, Vol: 286, Pages: 1-10, ISSN: 0045-6535
In-situ chemical regeneration of granular activated carbon (GAC) may represent an advantageous alternative to conventional off-site thermal regeneration in water treatment applications. The performance of chemical regeneration of carbon exhausted by metaldehyde and isoproturon was investigated using rapid small-scale column tests, performed using a sequence of pesticide adsorption and chemical regeneration cycles with a novel alkaline-organic regenerant solution. A fresh regenerant solution was able to achieve 82% and 45% regeneration of carbon exhausted by metaldehyde and isoproturon, respectively. After the first regeneration, the performance declined slightly to 79%, and to 36% after the fourth regeneration. A comparison using a thermally regenerated (operational) carbon suggested that chemical regeneration was more beneficial for carbon exhausted by metaldehyde. The regenerant solution has a potential to be re-used multiple times, thereby minimizing the amount of waste chemicals generated. A series of carbon characterization tests showed that chemical regeneration did not alter the surface area, pore size distribution and surface chemistry of the carbon. As part of the evaluation, the adsorption thermodynamics of virgin and chemically regenerated carbons were determined using isothermal titration calorimetry to evaluate the adsorption behaviour of the pesticides on the carbon samples. The relatively high regeneration efficiency achieved by chemical regeneration, and minimal deleterious effect to the physico-chemical properties of the carbon, demonstrated the beneficial potential of this process as an alternative to conventional thermal regeneration of GAC.
Larasati A, Fowler GD, Graham NJD, 2021, Insights into chemical regeneration of activated carbon for water treatment, Journal of Environmental Chemical Engineering, Vol: 9, ISSN: 2213-3437
Granular activated carbon (GAC) adsorption has found wide application as a treatment process for the removal of natural organic matter, small organic compounds (e.g. pesticides), inorganic compounds (e.g. heavy metals), taste and odour compounds in water over many years. During GAC operation, contaminants are adsorbed and the carbon becomes progressively saturated over time, requiring periodic regeneration of the media to restore its capacity. Chemical regeneration has been identified as an effective alternative to off-site thermal regeneration, which is the most commonly practiced carbon regeneration technique for carbon exhausted by organic contaminants. Off-site thermal regeneration poses significant disadvantages as it is a time-consuming process and represents a significant operational cost (e.g. reduced productivity) and environmental (energy/CO2) burden to water utilities. Chemical regeneration can be performed on-site, either in situ or off-line, by exposing the spent (exhausted) GAC to a selected chemical, or a combination of chemicals, to remove the adsorbed contaminants. Prior research on chemical regeneration has been limited in extent, but has considered both organic and inorganic solutions. Despite a significant number of studies, a suitable regenerant solution for desorbing a wide range of aqueous contaminants in drinking water treatment has not been identified to-date. In this paper, we provide a critical review of the performance of alternative regenerant solutions for the chemical regeneration of GAC loaded with different organic contaminants.
Krueger BC, Fowler GD, Templeton MR, 2021, Critical analytical parameters for faecal sludge characterisation informing the application of thermal treatment processes, Journal of Environmental Management, Vol: 280, ISSN: 0301-4797
Thermal processes for the treatment of faecal sludge such as pyrolysis or combustion offer complete destruction of pathogens, whilst allowing for energy and nutrient recovery. The development of such processes is currently constrained by a lack of knowledge on thermally relevant faecal sludge characteristics. This study investigated thirty faecal sludge samples from three sanitation technologies (ventilated improved pit latrines (VIP), urine diverting dry toilets (UD), septic tanks (ST)) and compared these by non-parametric statistical analysis. A focus was placed on parameters necessary for thermal process development and recoverable nutrient concentrations. The relevant characteristics ranged widely within technology groups. Calorific values and ash concentrations of 2.1–25.7 MJ/kg and 9.5–88.4% were observed for STs, of 9.2–13.9 MJ/kg and 40.9–61.5% for VIPs and of 3.9–18.1 MJ/kg and 18.8–81.3% for UDs. These two parameters show a strong linear inverse correlation and determine the minimum dewatering requirements from which a net energy recovery may be possible. Results suggest that more than 90% of samples can meet these requirements following commonly used dewatering technologies. A comparison across technologies provided strong evidence that the faecal sludge source significantly influences sludge composition, emphasized by higher median ratios of fixed carbon to volatile matter in VIPs (0.23) and UDs (0.23) compared to STs (0.15). The sanitation technology also influenced recoverable nutrient concentrations, with phosphorus and potassium concentrations generally ranging between 5.8–49.2 g/kg and 1.4–26.1 g/kg respectively. Compared to STs, median concentrations of phosphorus and potassium in VIPs were 3.4 and 3.8 times higher respectively, and 3.0 and 8.8 times higher in UDs. The findings highlight the importance of considering the faecal sludge source in the development of thermal treatment processes. This stud
Bowles AJ, Fowler GD, O'Sullivan C, et al., 2020, Sustainable rubber recycling from waste tyres by waterjet: A novel mechanistic and practical analysis, Sustainable Materials and Technologies, Vol: 25, Pages: 1-15, ISSN: 2214-9937
Production and disposal of car tyres are major contributors to environmental damage. The first stage in tyre rubber recycling is granulation to smaller particle sizes. The sub-optimal physical, mechanical and chemical properties of mechanically ground tyre rubber (GTR) when incorporated into recycled blends are major obstacles to wider use of this potentially sustainable, recovered resource. Consequently, newly manufactured tyres contain less than 5% recycled material. This study compares two types of GTR product: mechanically ground crumb (MGC) and ultrahigh pressure waterjet-produced rubber crumb (WJC). A novel image analysis method showed that when the two particle types were compared, MGC was associated with both greater convexity and sphericity: the geometric mean ratio of MGC/WJC sphericity was 1.67. When part-recycled rubber blends comprising 30% crumb of particle size < 300 μm were compared to virgin polymer, the WJC blend exhibited superior mechanical properties to the MGC blend. These results can be explained by the higher surface area to volume ratio of WJC when compared to MGC which results in strong bonding in new blends using WJC. Further analysis by scanning electron microscopy (SEM) elucidated significant shape and textural variation within the WJC sample, allowing grouping into two sub-categories: “W1” which comprises particles with complex geometries, and “W2” particles which have a relatively simple topology that is similar to MGC. Maximising the W1:W2 particle ratio is likely to be crucial to the optimisation of output quality in the WJC process, and so a composite model is proposed that unifies three well-established fluid effects: brittle fracturing, impact cratering and cavitation. Impact cratering and cavitation effects should be maximised by altering process parameters with the aim of producing a higher proportion of crumb with a more irregular surface morphology to achieve better bonding properties in recycled
Larasati A, Fowler GD, Graham NJD, 2020, Chemical regeneration of granular activated carbon: preliminary evaluation of alternative regenerant solutions, Environmental Science: Water Research & Technology, Vol: 6, Pages: 2043-2056, ISSN: 2053-1400
Granular activated carbon (GAC) is used in drinking water treatment plants worldwide to remove micro-pollutants such as pesticides. Early breakthrough of problematic micro-pollutants leads to frequent and costly thermal regeneration off-site. A potential alternative approach is to chemically regenerate GAC on-site (possibly in situ) with an appropriate solution capable of desorbing organic contaminants, having a range of physico-chemical properties. In this study, four types of regenerant solution were evaluated in batch tests for their ability to desorb five target contaminants. The solutions were: high purity water, sodium hydroxide, ethanol, and a mixture of sodium hydroxide and ethanol. The contaminants included: phenol and nitrobenzene, as representative aromatic compounds; clopyralid and metaldehyde, as poorly-adsorbed pesticides; and isoproturon, a well-adsorbed pesticide. Among the properties of the contaminants, their hydrophobicity and aqueous solubility had the most significant influence on the desorption efficiency. NaOH/CH3CH2OH was found to be more effective than individual solutions in desorbing the target contaminants, indicating an ability to desorb both hydrophobic and hydrophilic compounds. The NaOH/CH3CH2OH regenerant solution yielded desorption efficiencies in the range of approximately 40–90%, with the efficiency dependent on the contaminant. A thermodynamic study provided valuable fundamental information regarding the adsorption and desorption mechanisms, and the existence of two binding sites involving a weak physisorption and a stronger chemisorption-like interaction between the contaminants and the GAC.
Fan Y, Fowler GD, Zhao M, 2020, The past, present and future of carbon black as a rubber reinforcing filler - A review, JOURNAL OF CLEANER PRODUCTION, Vol: 247, ISSN: 0959-6526
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Krueger BC, Fowler GD, Templeton MR, et al., 2020, Resource recovery and biochar characteristics from full-scale faecal sludge treatment and co-treatment with agricultural waste, Water Research, Vol: 169:115253, ISSN: 0043-1354
Unsafe disposal of faecal sludge from onsite sanitation in low-income countries has detrimental effects on public health and the environment. The production of biochar from faecal sludge offers complete destruction of pathogens and a value-added treatment product. To date, research has been limited to the laboratory. This study evaluates the biochars produced from the co-treatment of faecal sludge from septic tanks and agricultural waste at two full-scale treatment plants in India by determining their physical and chemical properties to establish their potential applications. The process yielded macroporous, powdery biochars that can be utilised for soil amendment or energy recovery. Average calorific values reaching 14.9 MJ/kg suggest use as solid fuel, but are limited by a high ash content. Phosphorus and potassium are enriched in the biochar but their concentrations are restricted by the nutrient-depleted nature of septic tank faecal sludge. High concentrations of calcium and magnesium led to a liming potential of up to 20.1% calcium carbonate equivalents, indicating suitability for use on acidic soils. Heavy metals present in faecal sludge were concentrated in the biochar and compliance for soil application will depend on local regulations. Nevertheless, heavy metal mobility was considerably reduced, especially for Cu and Zn, by 51.2–65.2% and 48.6–59.6% respectively. Co-treatment of faecal sludge with other carbon-rich waste streams can be used to influence desired biochar properties. In this case, the addition of agricultural waste increased nutrient and fixed carbon concentrations, as well as providing an additional source of energy. This study is a proof of concept for biochar production achieving full-scale faecal sludge treatment. The findings will help inform appropriate use of the treatment products as this technology becomes more commonly applied.
Cheok Q, Kuenzel C, Smith SR, et al., 2020, Investigation of carbonization process parameters to manage Japanese knotweed (<i>Fallopia japonica</i>) in the UK, 5th International Conference of Chemical Engineering and Industrial Biotechnology (ICCEIB), Publisher: IOP PUBLISHING LTD, ISSN: 1757-8981
Reyna-Bensusan N, Wilson DC, Davy PM, et al., 2019, Experimental measurements of black carbon emission factors to estimate the global impact of uncontrolled burning of waste, ATMOSPHERIC ENVIRONMENT, Vol: 213, Pages: 629-639, ISSN: 1352-2310
Open burning is a widely practiced method of solid waste disposal in many regions of the world and represents a significant source of air pollution. Black carbon (BC) is a particularly serious air pollutant emitted from the uncontrolled burning of waste in open fires because it has a global warming potential (GWP) up to 5000 times greater than carbon dioxide (CO2) and is also linked to detrimental health impacts. However, few quantitative measurements of BC from open burning have been completed to establish the extent and impacts of this emission source on the environment. Emission factors (EFs) for BC from burning mixed solid waste samples were measured in the laboratory based on waste compositions in a representative developing country (Mexico). Black carbon EFs were also derived for individual waste types, including: green waste, different types of plastics, textiles and paper and cardboard. Individual waste BC EFs were combined using waste composition data from different areas of the world to estimate regional and global BC emissions from this source. The results demonstrated that BC emissions from open burning of waste have a significant climate impact, equivalent to 2–10% of global CO2Eq emissions. Global BC CO2Eq emissions from burning waste are 2–8 times larger compared to methane (CH4) CO2Eq emissions arising from the decomposition of equivalent amounts of combustible biodegradable waste disposed at dumpsites. Action to reduce open burning of waste would have a significant and immediate benefit to improving air quality and reducing the potential impact on climate change.
Bond T, Tse Q, Chambon C, et al., 2018, The feasibility of char and bio-oil production from pyrolysis of pit latrine sludge, Environmental Science: Water Research and Technology, Vol: 4, Pages: 253-264, ISSN: 2053-1400
Sustainable methods are required in developing regions to treat and recover value from pit latrine sludge. One strategy is to pyrolyse pit latrine contents and generate char and bio-oil, which can then be used as a soil enhancer and fuel, respectively. Despite the many benefits associated with the process, there is very limited relevant literature available. This study examines its feasibility. Initially, the energy balance for the pyrolysis of sewage sludge was calculated using data from 14 literature studies. The average net energy recovery from pyrolysis of dewatered and dried sewage sludge followed by use of bio-oil as fuel was calculated as 4.95 ± 0.61 MJ kg−1. For dewatered sewage sludge, an average net energy input of 2.23 ± 0.31 MJ kg−1 was required. Parallel calculations were undertaken where pit latrine sludge with 0–100% water content was the hypothetical feedstock. On average, net energy recovery from produced bio-oil was achievable when pit latrine sludge with a water content of ≤∼55% was the feedstock. When both bio-oil and char were utilised, net energy recovery was feasible at a water content value of ≤∼65%. Char production is more favourable from stabilised pit latrine sludge with lower moisture and volatile solids content. Barriers to the pyrolysis of pit latrine sludge include its heterogeneous composition and the difficulty of collecting high-viscosity sludge. Overall, this study demonstrates the potential of pyrolysis as a disposal and value addition method for pit latrine sludge. Innovative methods for sludge drying and pit emptying will expedite the process becoming a reality.
Bond T, Tse Q, Chambon CL, et al., 2017, The feasibility of char and bio-oil production from pyrolysis of pit latrine sludge (Retraction of 10.1039/C7EW00132K, 2017), ENVIRONMENTAL SCIENCE-WATER RESEARCH & TECHNOLOGY, Vol: 3, Pages: 1171-1171, ISSN: 2053-1400
Bond T, Tse Q, Chambon CL, et al., 2017, The feasibility of char and bio-oil production from pyrolysis of pit latrine sludge, Environmental Science: Water Research and Technology, Vol: in press
Fan Y, Fowler GD, Norris C, 2017, Potential of a Pyrolytic Coconut Shell as a Sustainable Biofiller for Styrene-Butadiene Rubber, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 56, Pages: 4779-4791, ISSN: 0888-5885
Kumar S, Smith SR, Fowler G, et al., 2017, Challenges and opportunities associated with waste management in India, Royal Society Open Science, Vol: 4, ISSN: 2054-5703
India faces major environmental challenges associated withwaste generation and inadequate waste collection, transport,treatment and disposal. Current systems in India cannotcope with the volumes of waste generated by an increasingurban population, and this impacts on the environment andpublic health. The challenges and barriers are significant,but so are the opportunities. This paper reports on aninternational seminar on ‘Sustainable solid waste managementfor cities: opportunities in South Asian Association for RegionalCooperation (SAARC) countries’ organized by the Councilof Scientific and Industrial Research-National EnvironmentalEngineering Research Institute and the Royal Society. A priorityis to move from reliance on waste dumps that offer noenvironmental protection, to waste management systems thatretain useful resources within the economy. Waste segregationat source and use of specialized waste processing facilitiesto separate recyclable materials has a key role. Disposal ofresidual waste after extraction of material resources needsengineered landfill sites and/or investment in waste-to-energyfacilities. The potential for energy generation from landfill viamethane extraction or thermal treatment is a major opportunity,but a key barrier is the shortage of qualified engineers andenvironmental professionals with the experience to deliverimproved waste management systems in India.
Hua X, Fan Y, Wang Y, et al., 2017, The behaviour of multiple reaction fronts during iron (III) oxide reduction in a non-steady state packed bed for chemical looping water splitting, Applied Energy, Vol: 193, Pages: 96-111, ISSN: 0306-2619
Owing to the unclear temporal and spatial variations of axial solid conversion in a packed bed using iron (III) oxide as an oxygen carrier, we directly observe these variations by means of a sub-layer approach. The results indicate that the behaviour of the multiple reaction fronts during iron (III) oxide reduction by CO or H2 within a packed bed for chemical looping water splitting (CLWS) is strongly dependent on the reaction temperature. When the reaction temperature is lower than the merging temperature, three reaction fronts, i.e., Fe2O3-Fe3O4, Fe3O4-Fe0.947O and Fe0.947O-Fe, and three product zones, i.e., Fe3O4, Fe0.947O and Fe, will appear in the packed bed. In contrast, when the reaction temperature is higher than the merging temperature, the Fe2O3-Fe3O4 and Fe3O4-Fe0.947O fronts merge, leading to the disappearance of the Fe3O4 zone. As a result, only the Fe2O3-Fe0.947O and Fe0.947O-Fe fronts, as well as Fe0.947O and Fe zones will appear in the packed bed. These reduction behaviours are verified by two breakthrough curves, one for T < Tm and one for T > Tm, from the thermodynamically controlled reduction of iron (III) oxide in the packed bed. The reaction front movement model, which is proposed based on the reduction behaviour, can be used to determine the maximum solid conversion of the reduction step, i.e., the thermodynamic limitation of the reduction step, in the packed bed CLWS. The maximum solid conversion can reach 0.409 for the CO case and 0.554 for the H2 case. The first discovery of both the behaviours of the reaction fronts movement and the thermodynamic limitations of the reduction step standardizes the criteria for both the oxygen carrier evaluation and the optimization of the operating conditions and provides theoretical support for scaling up the packed bed and developing new technology for packed bed CLWS.
Dong S, Ochoa Gonzalez R, Harrison RM, et al., 2017, Isotopic signatures in atmospheric particulate matter suggest important contributions from recycled gasoline for lead and non-exhaust traffic sources for copper and zinc in aerosols in London, United Kingdom, ATMOSPHERIC ENVIRONMENT, ISSN: 1352-2310
The aim of this study was to improve our understanding of what controls the isotope composition of Cu, Zn and Pb in particulate matter (PM) in the urban environment and to develop these isotope systems as possible source tracers. To this end, isotope ratios (Cu, Zn and Pb) and trace element concentrations (Fe, Al, Cu, Zn, Sb, Ba, Pb, Cr, Ni and V) were determined in PM10 collected at two road sites with contrasting traffic densities in central London, UK, during two weeks in summer 2010, and in potential sources, including non-combustion traffic emissions (tires and brakes), road furniture (road paint, manhole cover and road tarmac surface) and road dust. The isotope signatures of other important sources (gasoline and exhaust emissions) were taken from previous published data. Iron, Ba and Sb were used as proxies for emissions derived from brake pads, and Ni, and V for emissions derived from fossil fuel oil. The isotopic composition of Pb (expressed using 206Pb/207Pb) ranged between 1.1137 and 1.1364. The isotope ratios of Cu and Zn expressed as δ65CuNIST976 and δ66ZnLyon ranged between -0.01‰ and +0.51‰ and between -0.21‰ and +0.33‰, respectively. We did not find significant differences in the isotope signatures in PM10 over the two weeks sampling period and between the two sites, suggesting similar sources for each metal at both sites despite their different traffic densities. The stable isotope composition of Pb suggests significant contribution from road dust resuspension and from recycled leaded gasoline. The Cu and Zn isotope signatures of tires, brakes and road dust overlap with those of PM10. The correlation between the enrichments of Sb, Cu, Ba and Fe in PM10 support the previously established hypothesis that Cu isotope ratios are controlled by non-exhaust traffic emission sources in urban environments (Ochoa Gonzalez et al., 2016). Analysis of the Zn isotope signatures in PM10 and possible sources at the two sites su
Yu W, Graham NJD, Fowler GD, 2016, Coagulation and oxidation for controlling ultrafiltration membrane fouling in drinking water treatment: Application of ozone at low dose in submerged membrane tank, Water Research, Vol: 95, Pages: 1-10, ISSN: 1879-2448
Coagulation prior to ultrafiltration (UF) is widely applied for treating contaminated surface water sources for potable supply. While beneficial, coagulation alone is unable to control membrane fouling effectively in many cases, and there is continuing interest in the use of additional, complementary methods such as oxidation in the pre-treatment of raw water prior to UF. In this study, the application of ozone at low dose in the membrane tank immediately following coagulation has been evaluated at laboratory-scale employing model raw water. In parallel tests with and without the application of ozone, the impact of applied ozone doses of 0.5 mg L−1 and 1.5 mg L−1 (approximately 0.18 mg L−1 and 0.54 mg L−1 consumed ozone, respectively) on the increase of trans-membrane pressure (TMP) was evaluated and correlated with the quantity and nature of membrane deposits, both as a cake layer and within membrane pores. The results showed that a dose of 0.5 mgO3 L−1 gave a membrane fouling rate that was substantially lower than without ozone addition, while a dose of 1.5 mgO3 L−1 was able to prevent fouling effects significantly (no increase in TMP). Ozone was found to decrease the concentration of bacteria (especially the concentration of bacteria per suspended solid) in the membrane tank, and to alter the nature of dissolved organic matter by increasing the proportion of hydrophilic substances. Ozone decreased the concentration of extracellular polymeric substances (EPS), such as polysaccharides and proteins, in the membrane cake layer; the reduced EPS and bacterial concentrations resulted in a much thinner cake layer, although the suspended solids concentration was much higher in the ozone added membrane tank. Ozone also decreased the accumulation and hydrophobicity of organic matter within the membrane pores, leading to minimal irreversible fouling. Therefore, the application of low-dose ozone within the UF membrane tank is a potentially
Smith KM, Fowler GD, Pullket S, et al., 2012, The production of attrition resistant, sewage-sludge derived, granular activated carbon, SEPARATION AND PURIFICATION TECHNOLOGY, Vol: 98, Pages: 240-248, ISSN: 1383-5866
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- Citations: 38
Stuber F, Smith KM, Baricot Mendoza M, et al., 2011, Sewage sludge based carbons for catalytic wet air oxidation of phenolic compounds in batch and trickle bed reactors, APPLIED CATALYSIS B-ENVIRONMENTAL, Vol: 110, Pages: 81-89, ISSN: 0926-3373
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- Citations: 48
Abbe OE, Grimes SM, Fowler GD, 2011, Decision support for the management of oil well drill cuttings, Proceedings of Institution of Civil Engineers: Waste and Resource Management, Vol: 164, Pages: 213-220, ISSN: 1747-6526
Depending on the hole size and mud type used in the drilling process, oil well drill cuttings can be a relatively high-volume solid waste stream from drilling operations in the oil and gas exploration and production industry. Current management practices tend to involve thermal treatment followed by landfill disposal. The waste-to-resource conversion approach, however, provides opportunities that are not reflected in the current management system. The drill cuttings waste management decision support tool described in this work allows for the consideration of alternative reuse applications such as in construction materials, oil well reinjection, wetlands restoration, and the manufacture of stable leach-resistant material such as glass ceramics, in a move to divert treated drill cuttings from landfill towards zero waste disposal.
Lampris C, Stegemann JA, Pellizon-Birelli M, et al., 2011, Metal leaching from monolithic stabilised/solidified air pollution control residues, JOURNAL OF HAZARDOUS MATERIALS, Vol: 185, Pages: 1115-1123, ISSN: 0304-3894
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- Citations: 34
Marques RRN, Stueber F, Smith KM, et al., 2011, Sewage sludge based catalysts for catalytic wet air oxidation of phenol: Preparation, characterisation and catalytic performance, APPLIED CATALYSIS B-ENVIRONMENTAL, Vol: 101, Pages: 306-316, ISSN: 0926-3373
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- Citations: 83
Lebigue CJ, Andriantsiferana C, Krou N, et al., 2010, Application of sludge-based carbonaceous materials in a hybrid water treatment process based on adsorption and catalytic wet air oxidation, JOURNAL OF ENVIRONMENTAL MANAGEMENT, Vol: 91, Pages: 2432-2439, ISSN: 0301-4797
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- Citations: 36
Abbe OE, Grimes SM, Fowler GD, et al., 2009, Novel sintered glass-ceramics from vitrified oil well drill cuttings, JOURNAL OF MATERIALS SCIENCE, Vol: 44, Pages: 4296-4302, ISSN: 0022-2461
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- Citations: 8
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