Publications
246 results found
Smith SR, Rigby H, 2024, The significance of lead entering the human food chain via livestock ingestion from the agricultural use of biosolids, with special reference to the UK., Sci Total Environ
Long-term application of biosolids to agricultural soils results in the slow accumulation of potentially toxic elements (PTEs), which are regulated by maximum permitted limit values to protect human health and the environment. Two programmes of UK government-funded (MAFF/DoE) research were commissioned in the 1990s to investigate the safety of the controls on PTEs in relation to the potential transfer to the food chain via the animal ingestion route by sheep grazing biosolids-amended soil. Here, we re-examine this evidence in the light of other recent research and revised food quality standards, to determine the significance of lead (Pb) accumulation in soil from the agricultural use of biosolids. Direct ingestion of biosolids-amended soil is the main transfer pathway of Pb to grazing livestock. The concentrations of Pb in muscle tissue of animals grazing biosolids-amended soil observed in the MAFF/DoE trials, and reported in the scientific literature, were generally small and similar to background, control values. Lambs and ewes ingesting biosolids-amended soil with a total Pb concentration > 200 mg kg-1 ds at a rate of 10 % in the diet exceeded the current maximum permitted concentration of Pb in offal (0.5 mg kg-1 fresh weight (FW)). However, the decline in PTE concentrations found in biosolids, due to improved industrial practices and stricter controls on the emissions of contaminants to the environment in general and wastewater in particular, has mitigated the risk of Pb accumulation above the food quality standard for this element in offal. Given the significant improvements in biosolids quality, and particularly the Pb content, regulatory soil and sludge limits for Pb are no longer likely to have a practical or significant impact on the amount of Pb entering the food chain through the animal ingestion route from biosolids-amended agricultural soil.
Bünemann EK, Reimer M, Smolders E, et al., 2024, Do contaminants compromise the use of recycled nutrients in organic agriculture? A review and synthesis of current knowledge on contaminant concentrations, fate in the environment and risk assessment, Science of the Total Environment, Vol: 912, ISSN: 0048-9697
Use of nutrients recycled from societal waste streams in agriculture is part of the circular economy, and in line with organic farming principles. Nevertheless, diverse contaminants in waste streams create doubts among organic farmers about potential risks for soil health. Here, we gather the current knowledge on contaminant levels in waste streams and recycled nutrient sources, and discuss associated risks. For potentially toxic elements (PTEs), the input of zinc (Zn) and copper (Cu) from mineral feed supplements remains of concern, while concentrations of PTEs in many waste streams have decreased substantially in Europe. The same applies to organic contaminants, although new chemical groups such as flame retardants are of emerging concern and globally contamination levels differ strongly. Compared to inorganic fertilizers, application of organic fertilizers derived from human or animal feces is associated with an increased risk for environmental dissemination of antibiotic resistance. The risk depends on the quality of the organic fertilizers, which varies between geographical regions, but farmland application of sewage sludge appears to be a safe practice as shown by some studies (e.g. from Sweden). Microplastic concentrations in agricultural soils show a wide spread and our understanding of its toxicity is limited, hampering a sound risk assessment. Methods for assessing public health risks for organic contaminants must include emerging contaminants and potential interactions of multiple compounds. Evidence from long-term field experiments suggests that soils may be more resilient and capable to degrade or stabilize pollutants than often assumed. In view of the need to source nutrients for expanding areas under organic farming, we discuss inputs originating from conventional farms vs. non-agricultural (i.e. societal) inputs. Closing nutrient cycles between agriculture and society is feasible in many cases, without being compromised by contaminants, and should be
Rigby H, Dowding A, Fernandes A, et al., 2023, Transfer of polychlorinated, polybrominated and mixed-halogenated dioxins, furans and biphenyls, polychlorinated naphthalenes and alkanes, polycyclic aromatic hydrocarbons and chlorobenzenes to the milk of dairy cattle from controlled ingestion of industrial and municipal bioresources recycled to agricultural land, Science of the Total Environment, Vol: 886, Pages: 1-16, ISSN: 0048-9697
Recycled bioresources (biosolids, compost-like-output, meat and bonemeal ash, poultry litter ash, paper sludge ash) were added to the feed of dairy cattle to simulate incidental ingestion from agricultural utilisation, to investigate the transfer of organic contaminants from the ingested materials to milk. The bioresources were blended with a loamy sand soil at agronomic rates to simulate a single application to land, which was added to the diet at 5 % of the total intake on a dry matter (DM) basis. Biosolids, and control treatments consisting of unamended soil, were also added directly to the feed at 5 % DM. The cattle were fed the bioresource amended diets for a target period of three to four weeks, depending on material, and monitoring continued for four weeks after treatment withdrawal. Milk samples were taken weekly with chemical analysis of selected samples for a range of organic contaminants including: polychlorinated, polybrominated and mixed-halogenated dioxins, furans and biphenyls, polychlorinated naphthalenes and alkanes (often called chlorinated paraffins), polycyclic aromatic hydrocarbons and chlorobenzenes. No statistically significant additional transfer of organic contaminants to the milk was detected due to the relatively low levels of contaminants present when the bioresources were incorporated with soil at agronomic rates. However, direct biosolids ingestion by cattle significantly increased the transfer of contaminants to milk in comparison to control animals. Although present in larger concentrations in biosolids than their chlorinated counterparts, the carry over rates and bioconcentration factors of brominated dioxins and furans were considerably smaller. Direct ingestion of biosolids resulted in most contaminants approaching, but not always completely reaching, steady state concentrations within the treatment feeding period, however, concentrations generally declined to control values within four-weeks after withdrawing the biosoli
Liu Z, Smith SR, 2023, Cross-linked enzyme aggregate (CLEA) preparation from waste activated sludge, Microorganisms, Vol: 11, Pages: 1-21, ISSN: 2076-2607
Enzymes are used extensively as industrial bio-catalysts in various manufacturing and processing sectors. However, commercial enzymes are expensive in part due to the high cost of the nutrient medium for the biomass culture. Activated sludge (AS) is a waste product of biological wastewater treatment and consists of microbial biomass that degrades organic matter by producing substantial quantities of hydrolytic enzymes. Recovering enzymes from AS therefore offers a potential alternative to conventional production techniques. A carrier-free, cross-linked enzyme aggregate (CLEA) was produced from crude AS enzyme extract for the first time. A major advantage of the CLEA is the combined immobilization, purification, and stabilization of the crude enzymes into a single step, thereby avoiding large amounts of inert carriers in the final enzyme product. The AS CLEA contained a variety of hydrolytic enzymes and demonstrated high potential for the bio-conversion of complex organic substrates.
Smith S, Jiang L, Pettitt T, et al., 2022, A critical review of the physiological, ecological, physical and chemical factors influencing the microbial degradation of concrete by fungi, Building and Environment, Vol: 214, ISSN: 0007-3628
Concrete is the most extensively used material in construction and is generally relatively resistant, but under certain environmental conditions it is susceptible to microbially influenced degradation (MID) by bacteria, algae and fungi. Filamentous fungi, including Fusarium oxysporum, Aspergillus niger and Cladosporium sphaerospermum, are widely detected on corroded concrete surfaces. However, in contrast to bacteria, the extent of, and factors influencing, fungal influenced degradation (FID) of concrete are poorly understood. The extensive presence and survival ability of fungi in concrete may be explained by their remarkable environmental adaptability and capacity to modify potentially extreme environments, including alkaline pH conditions found in concrete, facilitating its exploitation by, and growth of, the organism. Furthermore, fungi produce dormant, resistant spores that remain viable and survive for long periods of time, cellular autolysis conserves resources to maintain viability and growth in low nutrient conditions, and the mycelial network facilitates the transport of nutrients, substrates, water and oxygen (O2) within fungal colonies. The concrete environment is rich in calcium (Ca), which is essential for hyphal growth, and the requirement for this important nutrient may explain why fungi grow in and exploit concrete as a resource. The identified mechanisms responsible for the FID of concrete, include: (1) the formation and leaching of soluble Ca salts from the reaction of organic acids secreted by fungal cells with Ca in concrete; (2) expansion due to formation of insoluble Ca salts, such as Ca citrate, from the reaction with fungal organic acids; (3) crack development by ettringite formation from the secretion of the enzyme, keratinase, and amino acids; and (4) potential mechanical attack by fungal hyphal growth and extension into solubilisation zones and cracks. The mechanisms of FID operate simultaneously and potentially have important, yet curren
Liu J, Smith S, 2022, The link between organic matter composition and the biogas yield of full-scale sewage sludge anaerobic digestion, Water Science and Technology, Vol: 85, Pages: 1-15, ISSN: 0273-1223
The principal parameters influencing anaerobic digestion (AD) of sewage sludge have been extensively studied in controlled laboratory experiments, but the effects of sludge composition on full-scale systems have received relatively little attention. Sludge samples from eight major wastewater treatment plants (WWTPs) in the UK were examined to determine the effects of sludge composition on digestion performance. The biogas yield (BY) was estimated by two different methods: (1) a standard approach based on the reduction in volatile solids (VS), and (2) a more detailed mass balance of major constituent fractions of organic matter in sludge. The results showed that BY increased significantly with the overall amount of VS contained in digester feed sludge. In terms of the effects of individual fractions, BY was significantly related to and increased with the fat and cellulose contents in raw sludge, consistent with the high calorific value of fat and the digestibilities of both substrates, relative to the other major organic components. The results demonstrated the importance of sludge composition on digester performance and strategies to maximise BY were identified, for instance, by increasing codigestion of high fat containing substrates, and by utilising fat, oil and grease collected in-sewer and at WWTP.
Chung N, Cram T, Smith SR, et al., 2022, Development of a Cloud-based Data Match-Up Service (CDMS) in Support of Ocean Science Applications, OCEANS Hampton Roads Conference, Publisher: IEEE, ISSN: 0197-7385
Liu Z, Smith S, 2021, Enzyme recovery from biological wastewater treatment, Waste and Biomass Valorization, Vol: 12, Pages: 4185-4211, ISSN: 1877-2641
Enzymes are high value industrial bio-catalysts with extensive applications in a wide range of manufacturing and processing sectors, including the agricultural, food and household care industries. The catalytic efficiency of enzymes can be several orders higher compared to inorganic chemical catalysts under mild conditions. However, the nutrient medium necessary for biomass culture represents a significant cost to industrial enzyme production. Activated sludge (AS) is a waste product of biological wastewater treatment and consists of microbial biomass that degrades organic matter by producing substantial quantities of hydrolytic enzymes. Therefore, enzyme recovery from AS offers an alternative, potentially viable approach to industrial enzyme production. Enzyme extraction from disrupted AS flocs is technically feasible and has been demonstrated at experimental-scale. A critical review of disruption techniques identified sonication as potentially the most effective and suitable method for enzyme extraction, which can be scaled up and is a familiar technology to the water industry. The yields of different enzymes are influenced by wastewater treatment conditions, and particularly the composition, and can also be controlled by feeding sludge with specific target substrates. Nevertheless, hydrolytic enzymes can be effectively extracted directly from waste AS without specific modifications to standard wastewater treatment processes. Purification, concentration and stabilisation/immobilisation techniques can also greatly expand the industrial application and increase the economic value and marketability of enzyme products extracted from AS. Concentrated and purified AS enzymes could readily substitute inorganic and/or commercial bioenzyme catalysts in many industrial applications including, for example, leather processing, and in detergent and animal feed formulation. Enzyme extraction from AS therefore offers significant economic benefits to the Water Industry by recover
Smith S, Liu J, Liu S, 2021, A contemporary and historical analysis of the trace element composition of sewage sludge in the United Kingdom, Water and Environment Journal, Vol: 35, Pages: 892-901, ISSN: 1747-6585
Sewage sludge is the essential by‐product of wastewater treatment and approaching 100% of the sludge generated in the United Kingdom is recycled to agricultural land. In collaboration with three major Water Utility companies in the United Kingdom, a critical statistical analysis of historical and contemporary sludge quality data was completed to demonstrate the long‐term patterns and improvements in the trace element (TE) content of sludge recycled to agriculture since 1989, and to indicate the current status of sludge quality in the United Kingdom. Comparisons with pollutant emission inventory data showed most of the TE concentrations in sludge were strongly linked to declining environmental emissions. A soil accumulation model showed that zinc and copper would be the first to approach their statutory soil limits in the long term and that nickel, cadmium, lead and mercury are no longer significant and, from a practical perspective, could be removed from the regulatory controls on agricultural use.
Smith S, Rigby H, Dowding A, et al., 2021, Concentrations of organic contaminants in industrial and municipal bioresources recycled in agriculture in the UK, Science of the Total Environment, Vol: 765, Pages: 1-21, ISSN: 0048-9697
Many types of bioresource materials are beneficially recycled in agriculture for soil improvement and as alternative bedding materials for livestock, but they also potentially transfer contaminants into plant and animal foods. Representative types of industrial and municipal bioresources were selected to assess the extent of organic chemical contamination, including: (i) land applied materials: treated sewage sludge (biosolids), meat and bone meal ash (MBMA), poultry litter ash (PLA), paper sludge ash (PSA) and compost-like-output (CLO), and (ii) bedding materials: recycled waste wood (RWW), dried paper sludge (DPS), paper sludge ash (PSA) and shredded cardboard. The materials generally contained lower concentrations of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) relative to earlier reports, indicating the decline in environmental emissions of these established contaminants. However, concentrations of polycyclic aromatic hydrocarbons (PAHs) remain elevated in biosolids samples from urban catchments. Polybrominated dibenzo-p dioxins/dibenzofurans (PBDD/Fs) were present in larger amounts in biosolids and CLO compared to their chlorinated counterparts and hence are of potentially greater significance in contemporary materials. The presence of non ortho polychlorinated biphenyls (PCBs) in DPS was probably due to non-legacy sources of PCBs in paper production. Flame retardent chemicals were one of the most significant and extensive groups of contaminants found in the bioresource materials. Decabromodiphenylether (deca-BDE) was the most abundant polybrominated diphenyl ether (PBDE) and may explain the formation and high concentrations of PBDD/Fs detected. Emerging flame retardant compounds, including: decabromodiphenylethane (DBDPE) and organophosphate flame retardants (OPFRs), were also detected in several of the materials. The profile of perfluoroalkyl substances (PFAS) depended on the type of waste category
Liu J, Smith S, 2020, A multi-level biogas model to optimise the energy balance of full-scale sewage sludge conventional and THP anaerobic digestion, Renewable Energy, Vol: 159, Pages: 756-766, ISSN: 0960-1481
Anaerobic digestion (AD) is a long-established method for treating wastewater sludge and has been extensively researched, but there remains a lack of generic or practical modelling tools to guide operators and maximise the energy output. Detailed kinetic models have been developed, but are too complex as practical tools for industrial level application. A multi-level model of biogas yield (BY) was therefore developed based on operational data from 72 full-scale sites in the UK showing a wide range of AD performance. The model focused on the controllable operational parameters that are currently monitored at full-scale, including: temperature, hydraulic retention time and dry solids content in the feed sludge. The model effectively described performance variations in BY of full-scale processes, and provides a practical management tool to aid decision support to improve AD efficiency and net energy balance.
Smith S, Rigby H, 2020, The significance of cadmium entering the human food chain via livestock ingestion from the agricultural use of biosolids, with special reference to the UK, Environment International, Vol: 143, Pages: 1-10, ISSN: 0160-4120
When biosolids are applied to agricultural soil, potentially toxic elements (PTEs) accumulate in the topsoil, although it takes many repeated applications to reach soil limit values. Two programmes of UK government-funded research were commissioned in the 1990s to investigate the transfer of PTEs to the food chain via ingestion by sheep grazing biosolids- amended soil. Here, we critically re-examine this evidence in the light of other published work and current food quality standards. This was particularly motivated by the need to determine the safety of biosolids controls on PTEs in relation to revised and stricter European food quality controls for PTEs in foodstuff. The major pathway for transfer of PTEs to grazing livestock is via direct ingestion of biosolids or biosolids-amended soil from the soil surface. The main elements of concern for the human diet are cadmium (Cd) and lead (Pb), with Cd being the focus of the current paper. Animal ingestion of plant tissue is also a potential pathway for Cd exposure, which, unlike Pb, can transfer to crop tissues. The concentrations of Cd in the muscle tissue of sheep grazing biosolids-amended soil were generally small and similar to control values. Cadmium concentrations in sheep offal were below the maximum permitted concentration for human consumption. This was despite ingestion of soils exceeding the maximum permissible concentration for Cd in soil (3 mg kg-1 dry soil) by up to three times, at an ingestion rate of 10% total dietary dry matter intake. Grazing trials under practical conditions on high Cd soils demonstrated that the Cd concentrations in sheep offal remained below the food limit value for this element in offal from the combined intakes from biosolids-amended soil and herbage. Futhermore, given the substantial fall in environmental emissions and concentrations in biosolids of this element and, consequently, it cannot accumulate in soil to the limit value, biosolids Cd does not represent
Barber EA, Liu Z, Smith SR, 2020, Organic contaminant biodegradation by oxidoreductase enzymes in wastewater treatment, Microorganisms, Vol: 8, ISSN: 2076-2607
Organic contaminants (OCs), such as pharmaceuticals, personal care products, flame retardants, and plasticisers, are societally ubiquitous, environmentally hazardous, and structurally diverse chemical compounds whose recalcitrance to conventional wastewater treatment necessitates the development of more effective remedial alternatives. The engineered application of ligninolytic oxidoreductase fungal enzymes, principally white-rot laccase, lignin peroxidase, and manganese peroxidase, has been identified as a particularly promising approach for OC remediation due to their strong oxidative power, broad substrate specificity, low energy consumption, environmental benignity, and cultivability from lignocellulosic waste. By applying an understanding of the mechanisms by which substrate properties influence enzyme activity, a set of semi-quantitative physicochemical criteria (redox potential, hydrophobicity, steric bulk and pKa) was formulated, against which the oxidoreductase degradation susceptibility of twenty-five representative OCs was assessed. Ionisable, compact, and electron donating group (EDG) rich pharmaceuticals and antibiotics were judged the most susceptible, whilst hydrophilic, bulky, and electron withdrawing group (EWG) rich polyhalogenated compounds were judged the least susceptible. OC susceptibility scores were in general agreement with the removal rates reported for experimental oxidoreductase treatments (R2 = 0.60). Based on this fundamental knowledge, and recent developments in enzyme immobilisation techniques, microbiological enzymic treatment strategies are proposed to formulate a new generation of biological wastewater treatment processes for the biodegradation of environmentally challenging OC compounds.
Liu Z, Smith SR, 2020, Enzyme activity of waste activated sludge extracts., Water Sci Technol, Vol: 80, Pages: 1861-1869, ISSN: 0273-1223
Wastewater treatment and generated biological sludge provide an alternative source of enzymes to conventional industrial production methods. Here, we present a protocol for extracting enzymes from activated sludge using ultrasonication and surfactant treatment. Under optimum conditions, ultrasound disruption of activated sludge gave recovery rates of protease and cellulase enzymes equivalent to 63.1% and ∼100%, respectively. The extracting of enzymes from activated sludge represents a potentially significant, high-value, resource recovery option for biological sludge generated by municipal wastewater treatment.
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.
Grimes SM, Ciuffa F, Cooper J, et al., 2018, Development of a vacuum-packing system for food waste from urban catering facilities, Proceedings of the Institution of Civil Engineers. Waste and Resource Management., Vol: 171, Pages: 114-120, ISSN: 1747-6526
A novel vacuum-packing system is developed for food waste storage and collection under the conditions found in high-density urban and metropolitan catering establishments that has the following beneficial outcomes: (a) a reduction of 38% in the volume of food waste to be stored for collection; (b) a reduction in the physical space required on-site for storage of multiple vacuum packs of waste; (c) containment of the food waste stored in sanitised conditions, thus maintaining the integrity of the waste and extending the useful life of the waste in terms of its ideal composition for optimum beneficial recovery by anaerobic digestion or in-vessel composting, and reducing problems due to odour and vermin; and (d) reduction in the number of vehicle movements required to transfer the wastes to treatment facilities and their environmental impacts, while also achieving savings of £13–16 per bin lift in London, along with a considerable reduction in overall cost.
Kong FE, Deighton MA, Thurbon NA, et al., 2018, Cryptosporidium parvum decay during air drying and stockpiling of mesophilic anaerobically digested sewage sludge in a simulation experiment and oocyst counts in sludge collected from operational treatment lagoons in Victoria, Australia., Journal of Water and Health, Vol: 16, Pages: 435-448, ISSN: 1477-8920
The inactivation of Cryptosporidium species oocysts during sewage sludge treatment is important to protect human health when the residual biosolids are applied to agricultural land. Quantifying the decay of Cryptosporidium species during sludge treatment for microbiological assurance purposes is difficult if low numbers are present in wastewater. The rate of decay of Cryptosporidium parvum oocysts during solar/air drying treatment and in sludge stockpiles in temperate environment conditions was simulated in laboratory inoculation experiments using sludge sampled from a mesophilic anaerobic digester. Oocyst numbers were also determined in settled lagoon sludge samples collected from three operational rural wastewater treatment plants (WWTPs). C. parvum oocysts were enumerated by immunomagnetic separation followed by staining with vital dyes and examination by confocal laser scanning microscopy. An air-drying/storage period equivalent to 11 weeks was required for a 1 log10 reduction of viable oocysts inoculated into digested sludge. Oocyst viability in air-dried and stored digested sludge decreased with time, but was independent of sludge desiccation and dry solids (DS) content. No oocysts were detected in sludge samples collected from the anaerobic digester, and the average concentration of oocysts found in settled lagoon sludge from the rural WWTP was 4.6 × 102 oocysts/g DS.
Reyna-Bensusan N, Wilson DC, Smith SR, 2018, Uncontrolled burning of solid waste by households in Mexico is a significant contributor to climate change in the country., Environmental Research, Vol: 163, Pages: 280-288, ISSN: 0013-9351
Uncontrolled burning of municipal solid waste (MSW) is an important source of air pollution and is wide spread in many developing countries, but only limited data quantify the extent of domestic open burning of household waste. Here, we present some of the first field data to be reported on the uncontrolled domestic burning of waste. A representative community of Mexico (Huejutla de Reyes Municipality) was investigated and household surveys, interviews with waste operators and a waste characterisation analysis were completed to assess the extent of, and factors controlling, the open burning of waste. Waste collection provision to rural communities was very limited and, consequently 92% of households in rural areas reported that they disposed of waste by uncontrolled burning in backyards or unofficial dumps. Overall, 24% of the total MSW generated in the Municipality was disposed by uncontrolled burning. Urban and periurban areas received twice-weekly collections and the rate of uncontrolled burning was considerably smaller compared to rural households, corresponding to approximately 2% of total waste generation. Carbon equivalency calculations showed that burning waste in backyards represented approximately 6% of the total and 8.5% of fuel related CO2Eq emissions by the municipality. Moreover, the equivalent carbon dioxide (CO2Eq) from black carbon (BC) emitted by uncontrolled burning in backyards was over fifteen times larger compared to methane (CH4) potentially released from equivalent amounts of combustible biodegradable waste disposal at the official dumpsite. An assessment of local respiratory health data showed the incidence of disease was higher in rural than in urban areas, when the opposite trend is typically observed in the international literature; given the high rate of burning activity found in rural areas we suggest that open burning of waste could be a major reason for the apparent poorer respiratory health status of the rural population and requires
Irwin R, Surapaneni A, Smith D, et al., 2017, Verification of an alternative sludge treatment process for pathogen reduction at two wastewater treatment plants in Victoria, Australia, Journal of Water and Health, Vol: 15, Pages: 626-637, ISSN: 1477-8920
At South East Water wastewater treatment plants (WwTPs) in Victoria, Australia, biosolids are stockpiled for three years in compliance with the State guidelines to achieve the highest pathogen reduction grade (T1), suitable for unrestricted use in agriculture and landscaping. However, extended stockpiling is costly, may increase odour nuisance and greenhouse gas emissions, and reduces the fertiliser value of the biosolids. A verification programme of sampling and analysis for enteric pathogens was conducted at two WwTPs where sludge is treated by aerobic and anaerobic digestion, air drying (in drying pans or solar drying sheds) and stockpiling, to enumerate and, if present, monitor the decay of a range of enteric pathogens and parasites. The sludge treatment processes at both WwTPs achieved T1 grade biosolids with respect to prescribed pathogenic bacterial numbers (<1 Salmonella spp. 50 g−1 dry solids (DS) and <100 Escherichia coli g−1 DS) and >3 log10 enteric virus reduction after a storage period of one year. No Ascaris eggs were detected in the influent to the WwTPs, confirming previous studies that the presence of helminth infections in Victoria is extremely low and that Ascaris is not applicable as a control criterion for the microbiological quality of biosolids in the region.
Wilson DC, Kanjogera JB, Soos R, et al., 2017, Operator models for delivering municipal solid waste management services in developing countries. Part A: The evidence base, Waste Management and Research, Vol: 35, Pages: 820-841, ISSN: 0734-242X
This article presents the evidence base for ‘operator models’ – that is, how to deliver a sustainable service through the interaction of the ‘client’, ‘revenue collector’ and ‘operator’ functions – for municipal solid waste management in emerging and developing countries. The companion article addresses a selection of locally appropriate operator models. The evidence shows that no ‘standard’ operator model is effective in all developing countries and circumstances. Each city uses a mix of different operator models; 134 cases showed on average 2.5 models per city, each applying to different elements of municipal solid waste management – that is, street sweeping, primary collection, secondary collection, transfer, recycling, resource recovery and disposal or a combination. Operator models were analysed in detail for 28 case studies; the article summarises evidence across all elements and in more detail for waste collection. Operators fall into three main groups: The public sector, formal private sector, and micro-service providers including micro-, community-based and informal enterprises. Micro-service providers emerge as a common group; they are effective in expanding primary collection service coverage into poor- or peri-urban neighbourhoods and in delivering recycling. Both public and private sector operators can deliver effective services in the appropriate situation; what matters more is a strong client organisation responsible for municipal solid waste management within the municipality, with stable political and financial backing and capacity to manage service delivery. Revenue collection is also integral to operator models: Generally the municipality pays the operator from direct charges and/or indirect taxes, rather than the operator collecting fees directly from the service user.
Liu J, Gao Y, Pearce P, et al., 2017, Statistical modelling anaerobic digestion for process optimization and bench-marking: a case study of E. coli inactivation across all Thames Water conventional sewage sludge treatment sites, Water and Environment Journal, Vol: 31, Pages: 498-507, ISSN: 1747-6593
Untreated sewage sludge potentially contains a wide range of enteric pathogens that present a risk to human health. Mesophilic anaerobic digestion (MAD) is the most-favoured process for sewage sludge treatment in the United Kingdom. It is a well-established approach to sludge stabilisation, but the mechanisms responsible for pathogen removal are poorly understood. Operational data collected by Thames Water from conventional MAD sites were statistically scrutinised to examine the effects of primary and secondary digestion on the removal of the enteric indicator bacteria, Escherichia coli, by using the IBM SPSS statistical software package for ANOVA, post-hoc and multiple regression analysis. The results showed that the process temperature conditions at the MAD plants were equivalent to or exceeded the minimum estimated by the analysis necessary to comply with the 2 log10 removal standard for E. coli. The results also showed that primary digestion conditions (specifically temperature) sublethally damaged E. coli and increased decay in secondary digestion and therefore over the whole digestion process.
Unc A, Alonso Camargo-Valero M, Smith SR, 2017, Algal Research, Special Issue Editorial: Wastewater and Algae; Risk, biofuels and long-term sustainability, Algal Research-Biomass Biofuels and Bioproducts, Vol: 24, Pages: A1-A1, ISSN: 2211-9264
Unc A, Monfet E, Potter A, et al., 2017, Note to Editor: Microalgae cultivation for wastewater treatment and biofuel production: a bibliographic overview of past and current trends, Algal Research-Biomass Biofuels and Bioproducts, Vol: 24, Pages: A2-A7, ISSN: 2211-9264
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.
Rigby H, Clarke BO, Pritchard DL, et al., 2016, A critical review of nitrogen mineralization in biosolids-amended soil, the associated fertilizer value for crop production and potential for emissions to the environment, SCIENCE OF THE TOTAL ENVIRONMENT, Vol: 541, Pages: 1310-1338, ISSN: 0048-9697
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Rigby H, Dowding A, Fernandes A, et al., 2015, Organic Contaminant Content and Physico-Chemical Characteristics of Waste Materials Recycled in Agriculture, Agriculture, Vol: 5, Pages: 1289-1328, ISSN: 2077-0472
A range of wastes representative of materials currently applied, or with future potential to be applied, to agricultural land in the UK as fertilisers and soil improvers or used as animal bedding in livestock production, were investigated. In addition to full physico-chemical characterization, the materials were analysed for a suite of priority organic contaminants. In general, contaminants were present at relatively low concentrations. For example, for biosolids and compost-like-output (CLO), concentrations of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) were approximately 1−10 and 5–50 times lower, respectively, than various proposed or implemented European limit values for these contaminants in biosolids or composts applied to agricultural land. However, the technical basis for these limits may require re-evaluation in some cases. Polybrominated, and mixed halogenated, dibenzo-p-dioxins/dibenzofurans are not currently considered in risk assessments of dioxins and dioxin-like chemicals, but were detected at relatively high concentrations compared with PCDD/Fs in the biosolids and CLOs and their potential contribution to the overall toxic equivalency is assessed. Other ‘emerging’ contaminants, such as organophosphate flame retardants, were detected in several of the waste materials, and their potential significance is discussed. The study is part of a wider research programme that will provide evidence that is expected to improve confidence in the use of waste-derived materials in agriculture and to establish guidelines to protect the food chain where necessary.
Angelonidi E, Smith SR, 2015, A comparison of wet and dry anaerobic digestion processes for the treatment of municipal solid waste and food waste, WATER AND ENVIRONMENT JOURNAL, Vol: 29, Pages: 549-557, ISSN: 1747-6585
Rigby HL, Acker S, Dowding A, et al., 2015, The physico-chemical properties and concentrations of organic contaminants in waste materials recycled in agriculture, Tinos2015 3rd International Conference on Sustainable Solid Waste Management
Brito LM, Mourao I, Coutinho J, et al., 2015, Co-composting of invasive <i>Acacia longifolia</i> with pine bark for horticultural use, ENVIRONMENTAL TECHNOLOGY, Vol: 36, Pages: 1632-1642, ISSN: 0959-3330
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