Resource Recovery Options Research Articles

Effect of culture history and carbon sources on polyhydroxyalkanoates production in activated sludge systems

ABSTRACT Polyhydroxyalkanoates (PHAs) are important and completely biodegradable alternatives to regular plastics, and they can be produced by activated sludge systems during wastewater treatment. Wastewaters with high organic content are being used for PHA production, which is an important resource recovery option. In this context, the effect of sludge retention time and different carbon sources, such as acetate, peptone-mixture and industrial wastewater (containing acetic acid (AA), lactic acid (LA) and propionic acid (PA)), on PHA storage was investigated. Oxygen utilisation rate (OUR) profiles were generated in respirometric tests and were evaluated by activated sludge modelling. Results showed that high storage (AA: 70%; LA: 49%; PA: 60% and industrial wastewater: 52%) was achievable in the feast phase even when the biomass was fed with a high organic acid content substrate to which it is not acclimated.

Investigating the characteristics of combustible fraction of legacy waste: A study on energy recovery potential and GHG emission quantification

In India, majority of the generated municipal solid waste (MSW) was dumped in poorly managed landfills and dumpsites over the past decades and is an environmental and health hazard. Landfill mining is a promising solution to reclaim these sites along with the recovery of resources (materials and energy). During landfill mining operations, the combustible fraction is one of the major components recovered and needs proper management for maximizing resource recovery. For the identification of appropriate resource recovery options, knowledge of the physicochemical characteristics is required. The present study aims to assess the depth-wise change in the composition of legacy waste and the physicochemical characteristics of the combustible fraction. Furthermore, a material flow analysis considering the incineration of combustible fraction was performed to estimate the energy generation potential and the associated greenhouse gas (GHG) emissions. The results of the compositional analysis of dry legacy waste revealed that the fine fraction (<4 mm soil-like material) was dominating with a share of 36%. The depth-wise analysis showed a decrease in the calorific value with increasing landfill depth, while no specific trend was observed for the other parameters analyzed, including proximate and ultimate analysis, and chlorine content. The material flow analysis performed for 100 tonnes of wet legacy waste indicated that 52 tonnes of waste is combustible fraction. The GHG emissions through incineration of one tonne of dry combustible fraction would be 1389 kg CO2-eq, with 1125 kWh of electrical energy generation potential.

Fecal sludge characterization, treatment, and resource recovery options: a state-of-the-art review on fecal sludge management.

A rise in population and urbanization demanded that a robust fecal sludge management (FSM) value chain be used to restructure the sanitation system throughout the world securely. A significant global need exists to adopt efficient and sustainable FSM. On-site sanitation systems (OSS) produce fecal sludge (FS). FS is produced when excreta and blackwater are combined and stored or treated, either alone or in combination with greywater. FS can be semisolid or slurry and raw or partially digested. Critical examination of FS characteristics, i.e., biochemical oxygen demand (BOD), chemical oxygen demand (COD), total solids (TS), and pathogen count, varies from 600-56,836mg/l, 6656 to 201,200mg/l, 830-123,000mg/l, and 105 to 109 E. coli/l of FS respectively. Helminth eggs range from 2500-25,000/l of FS. Public health and the environment are negatively impacted by septic tank overflows and the careless discharge of FS into open spaces affecting groundwater quality, water bodies, irrigation fields, open drains, places outside villages, etc. Thus, deciding on a proper treatment technology for FS before discharging it into open land or reusing FS is essential to create a pollution-free environment. This paper highlights the practices adopted for FSM under its different processes, such as collecting, characterization, treating, and reusing of on-site FS and bibliometric analysis on documents on fecal sludge. A thorough analysis has been carried out by reviewing all important literature available globally.

Biorefinery of Sewage Sludge: Overview of Possible Value-Added Products and Applicable Process Technologies

The disposal of excess biological sewage sludge from wastewater treatment is a growing environmental issue due to the vast quantities generated worldwide. For many years, sludge disposal has been considered an inevitable “nuisance” linked to the main task of wastewater treatment; recently, the issues relating to the presence of emerging pollutants in sludge have contributed to severe limitations on traditional disposal routes and increased process costs. As a consequence of the water industry’s approach to sustainability and circular economy principles, the investigation into options for sludge-embedded resource recovery has been increasing over time. Among these, the definition of biorefinery encompasses many processes used to process sewage sludge for biofuel and/or resource recovery. In addition to the “conventional” recovery of biogas and nutrients, biopolymers (PHAs and EPS), proteins, enzymes, biopesticides, and biofuels are among the “new” sludge extraction products that are being studied. Not all of the proposed technologies are, however, mature for industrial exploitation as yet. This paper presents an overview of possible product recovery from sludge biorefinery, with emphasis on recent developments, and on the benefits and limitations of applicable technologies for ensuring sustainability and environmental efficiency, through an analysis of the current literature.

Generation and Management of Faecal Sludge Quantities and Potential for Resource Recovery in Phnom Penh, Cambodia

At the current rate of progress, there will probably still be 2.8 billion people world-wide without safely managed sanitation by 2030. To incentivise and increase implementation of sustainable faecal sludge management (FSM), especially in low and middle-income countries like Cambodia, human waste must be regarded as a resource. However, planning data, e.g. on the quantities, composition and fate of faecal sludge after leaving households, are inadequate and lack accuracy. The aim of this study was to provide baseline data for effective FSM planning by sanitation stakeholders in Phnom Penh. This was done by quantifying sludge volumes generated, transport logistics and resource recovery potential to incentivise sustainable management. Interviews were conducted with users and emptying and transportation contractors, together with collection of technical data about on-site sanitation systems. Geographical coordinates of household sampling locations and disposal sites were also mapped. The results revealed that Cheung Ek and Kob Srov wetlands are the main recipients of faecal sludge collected in Phnom Penh with the amount of 18,800 m3 and 13,700 m3 annually, respectively. The analysis showed that faecal sludge in Phnom Penh contains valuable resources such as nitrogen (6 tons), phosphorus (13 tons) and energy (148-165 GWh) annually, but in-depth investigations of appropriate treatment options for resource recovery are required. Detailed documentation of the location of potential recoverable resources from faecal sludge would assist decision-makers in developing action plans for sustainable FSM in Phnom Penh and similar cities.

Environmental resilience and sustainability through green technologies: A case evidence from rural coastal India

Rural coastal regions in developing countries are generally neglected with respect to environmental issues. The present study examined the feasibility of green technologies such as rainwater harvesting (RWH), sand filtration (SF), and composting (in-vessel and pit) to recover from the environmental issues in the coastal rural regions using survey and geographic information systems considering a rural Indian case study. According to the results, RWH yielded 0.140 million litres per 100 m² rooftop in the area, while a maximum total dissolved solids removal of 52% was achieved using the SF alleviating the water concerns. Meanwhile, with a solid waste generation of 0.207 kg d-1 capita-1 comprising 79.81% organic fraction, composting becomes the best waste resource recovery option in the area. Pilot-scale studies of composting transformed organic wastes into compost manure rich in nutrients improving the soil quality. Further analysis using a multi-criteria decision-making approach revealed that the public interest in applying these technologies depends on investment costs, additional resources requirements, and governmental policies. With the scope of improved lifestyle and quality, the study proposes more future research over green technologies and their implementation and is also directed towards developing decentralized site-specific rural governmental policies to achieve sustainability goals.

Physico-chemical and biological treatment strategies for converting municipal wastewater and its residue to resources

An increase in urbanization and industrialization has not only contributed to an improvement in the lifestyle of people, but it has also contributed to a surge in the generation of wastewater. To date, conventional physico-chemical and biological treatment methods are widely used for the treatment of wastewater. However, the efficient operation of these systems require substantial operation and maintenance costs, and the application of novel technologies for the treatment and disposal of sludge/residues. This review paper focuses on the application of different treatment options such as chemical, catalyst-based, thermochemical and biological processes for wastewater or sludge treatment and membrane-based technologies (i.e. pressure-driven and non-pressure driven) for the separation of the recovered products from wastewater and its residues. As evident from the literature, a wide variety of treatment and resource recovery options are possible, both from wastewater and its residues; however, the lack of planning and selecting the most appropriate design (treatment train) to scale up from pilot to the field scale has limited its practical application. The economic feasibility of the selected technologies was critically analyzed and the future research prospects of resource recovery from wastewater have been outlined in this review.

Activation of biochar through exoenzymes prompted by earthworms for vermibiochar production: A viable resource recovery option for heavy metal contaminated soils and water

The industrial revolution and indiscriminate usage of a wide spectrum of agrochemicals account for the dumping of heavy metals in the environment. In-situ/ex-situ physical, chemical, and bioremediation strategies with pros and cons have been adopted for recovering metal contaminated soils and water. Therefore, there is an urgent requirement for a cost-effective and environment-friendly technique to combat metal pollution. Biochar combined with earthworms and vermifiltration is a suitable emerging technique for the remediation of metal-polluted soils and water. The chemical substances (e.g., sodium hydroxide, zinc chloride, potassium hydroxide, and phosphoric acid) have been used to activate biochar, which also faces several shortcomings. Studies reveal that extracellular enzymes have been used to activate biochar which is produced by earthworms and microbes that can alter the surface of the biochar. The present review focuses on the global scenario of metal pollution and its remediation through biochar activation using earthworms. The earthworms and biochar can produce “vermibiochar” which is capable of reducing the metal ions from contaminated water and soils. The vermifiltration can be a suitable technology for metal removal from wastewater/effluent. Thus, the biochar has a trick of producing entirely new options at a time when vermifiltration and other technologies are least expected. Further attention to the biochar-assisted vermifiltration of different sources of wastewater is required to be explored for the large-scale utilization of the process.

Waste-to-energy: Coal-like refuse derived fuel from hazardous waste and biomass mixture

This study aimed to develop Refuse Derived Fuel (RDF) with high Calorific Value (CV) from mixed hazardous wastes and biomass. The potential utilization of newly developed RDF in cement production as a fuel substitute for coal has been investigated. In this work, five types of mixed hazardous industrial wastes (rubber waste, mixed waste, paint sludge, palm oil sludge and wastewater treatment plant sludge) and three biomass types (sawdust, paddy husk and empty fruit bunch) have been used. The newly developed RDF developed in this study has a CV of approximately 18,652 kJ/kg, and its volatile matter, fixed carbon and ash content of 32 %, 40 % and 28 %, respectively. The study is revealed that substituting 5 ton/hour of RDF in the coal only emits about 301 mg/m3 of NOx, which is within the regulatory limits in Malaysia. Besides, the emission of heavy metals, including Zinc, Arsenic, Lead, Copper, Antimony, and Chromium, was also within the regulatory limits. RDF in cement manufacturing kilns is economically and environmentally attractive, as the combustion of RDF allows for a reduction of about 2.25 kg of CO2 per kg compared to coal. In terms of the efficiency of clinker and stack gas emission values, the substitution of 15 % of RDF to the coal at a feeding rate of 5 ton per hour in cement production did not cause any processing and quality issues in the existing cement production process. The result revealed that substituting 15 % of RDF with the coal in 5000 ton/day cement plant may reduce 112.8 USD/hour in operating cost. Additionally, 140 USD/hour of net saving could be achieved by saving 2.52 ton/hour of CO2 emitted from the cement production. Overall, the results concluded that RDF is a very promising resource recovery and waste treatment option for hazardous waste management.

Legacy iron and steel wastes in the UK: Extent, resource potential, and management futures

The iron and steel industry has a long tradition of bulk reuse of slags for a range of construction applications. Growing interest in recent years has seen slag resource recovery options extend to critical raw material recovery and atmospheric carbon capture. Full scale deployment of such technologies is currently limited in part by absent or partial inventories of slag deposit locations, data on composition, and volume estimates in many jurisdictions. This paper integrates a range of spatial information to compile a database of iron and steel slag deposits in mainland United Kingdom (UK) for the first time and evaluate the associated resource potential. Over 190 million tonnes of legacy iron and steel slag are present across current and former iron and steel working regions of the UK, with particular concentrations in the north west and north east of England, and central Scotland. While significant potential stockpiles of blast furnace and basic oxygen furnace slag could provide up to 0.9 million tonnes of vanadium and a cumulative carbon dioxide capture potential of 57–138 million tonnes, major management challenges for resource recovery are apparent. Over one third are located in close proximity to designated conservation areas which may limit resource recovery. Furthermore, land use analyses show that many of the sites have already been redeveloped for housing (nearly 30% urban cover). Deposits from recent decades in current or recently closed steel-working areas may have the greatest potential for resource recovery where such ambitions could be coupled with site restoration and regeneration efforts.

Pilot-scale constructed wetlands for swine wastewater treatment: Microbial community analysis in bacterioplankton and epiphyton and options for resource recovery

In this study, the abundance and structure of bacterial and denitrifying functional genes of epiphyton and bacterioplankton in pilot-scale surface flow constructed wetlands treating different ammonium nitrogen concentrations (∼0.2, 40, 170, and 230 mg/L) of swine wastewater were investigated by quantitative PCR. The gene abundance of denitrifiers in epiphyton outnumbered the gene abundance of denitrifiers in bacterioplankton (p < 0.01), e.g., nirK gene abundance: 1.6–4.5 × 107vs 0.23–1.5 × 104 copies/ng DNA. A nitrogen concentration-dependent microbial community structure was observed for epiphyton and bacterioplankton. Proteobacteria, Bacteroidetes, and Actinobacteria dominated at the phylum level in both epiphyton and bacterioplankton. The nirS gene abundance in both niches was negatively related to the dissolved oxygen and redox potential of wastewater, but it was positively related with the Bacteroidetes and Flavobacterium abundance. The results indicated that microbial community structure and abundance are distinct between epiphyton and bacterioplankton. This study also demonstrate that epiphytic biofilms play an important role in denitrification during the treatment of swine wastewater in constructed wetlands. Finally, since swine wastewater serves as an excellent source for nutrients, possible technological options including periphyton techniques for resource recovery from wastewater and future research prospective have been suggested.

A robust hybrid decision model to evaluate critical factors of reverse logistics implementation using Grey-DEMATEL framework

The rising electronics waste (e-waste), increased pollution, disposal issues and exploitation of natural resources have augmented ecological and resource scarcity problems. These problems can be abate by adopting reverse logistics (RL) implementation so, the environmental protection and resource recovery options such as reuse, refurbish, recycle, remanufacturing and proper disposal can be executed to deal and manage with the e-waste. The goal of this research work is to identifies, evaluate and analyze the factors for successful implementation of RL practices. Fifteen critical RL factors are recognized from pertinent literature and endorsed by industry professionals. This paper utilized Grey based Decision Making Trial and Evaluation Laboratory (DEMATEL) approach to sort the identified factors into cause and effect clusters. Grey DEMATEL resolves the problem of data uncertainty and impreciseness involves in decision making in analyzing the factors. The results of the study found that 11 RL factors came into causal cluster as vital factors and 4 RL factors into the effect cluster as fundamental problems factors. Among causal cluster, the highest ranked four influential factors are Top management commitment (RLF1) with weightage value 0.7604, RLF2 i.e. enforced government regulations with weightage value 0.6549, RLF6 i.e. environmental/green concerns factor with weightage value 0.5678 and RLF8 i.e. Waste minimization (especially e-waste) factor with weightage value 0.5113 are respectively. Similarly, among effect cluster, the most easily influenced two factors are “Market and competition factors” (RLF15) with weightage value (− 1.1207) and “Increased e-commerce” (RLF13) with weightage value (− 1.2855) respectively. A case example of an Indian electronics firm is taken to showcase the application of the proposed model. This paper can help supply chain managers and analysts in superior understanding of critical factors and increase the chances of practicing more effective and successful RL implementation in electronics industry. At the end, few key country and industry-specific recommendations are offered to support major decision for management and policy makers to embrace and successfully accomplish the reverse supply chain practices in India.

Estimation of fuel potential of faecal sludge in a water scarce city, a case study of Jaipur Urban, India

Abstract Non-sewer sanitation systems are widely implemented for treatment and management of faecal sludge (FS) and septage in developing nations. India became an open defecation free (ODF) country in 2019, with more than 90 million toilets at rural and urban level constructed to achieve this ODF status. Government of India also initiated a faecal sludge and septage management (FSSM) policy in 2017. This paper highlights the policy vision for the state of Rajasthan and predicts options for a safely managed sanitation system through exploring the fuel potential of faecal sludge generated in the city. The intended study is an attempt to valorize faecal sludge into a marketable product through determining the heat capacity of dried faecal sludge from different sources such as pit toilets, septic tanks etc. In the present work in urban Jaipur, which is already a water scarce city, various onsite sanitation systems were targeted to collect FS samples from different locations. It was observed that the FS generated has a high heating value of 13.96 MJ/kg, with total solids ranges from 7 to 9%. For a pragmatic resource recovery option, the experimental data observed is validated with a literature review.

Effect of selenate and thiosulfate on anaerobic methanol degradation usingactivated sludge.

Anaerobic bioconversion of methanol was tested in the presence of selenate (SeO42-), thiosulfate (S2O32-), and sulfate (SO42-) as electron acceptors. Complete SeO42- reduction occurred at COD:SeO42- ratios of 12 and 30, whereas ~ 83% reduction occurred when the COD:SeO42- ratio was 6. Methane production did not occur at the three COD:SeO42- ratios investigated. Up to 10.1 and 30.9% of S2O32- disproportionated to SO42- at COD:S2O32- ratios of 1.2 and 2.25, respectively, and > 99% reduction was observed at both ratios. The presence of S2O32- lowered the methane production by 73.1% at a COD:S2O32- ratio of 1.2 compared to the control (no S2O32-). This study showed that biogas production was not preferable for SeO42- and S2O32--rich effluents and volatile fatty acid production could be a potential resource recovery option.

The application of Refuse Derived Fuel (FDR) from commercial solid wastes to reduce CO2 emissions in the cement industry: a preliminary study

One of the issues faced by several cities in Indonesia is the management of their increasing generation of solid wastes. One of the largest waste generators include the commercial area, such as malls, restaurants, office buildings, motels, and others, which need to manage their wastes via more sustainable routes such as the application of these wastes as refuse derived fuel to mitigate the climate change causing by fossil fuel. This study aims to analyse the potential use of wastes generated from commercial areas such as refuse-derived fuel (RDF) in the cement industry for reducing CO2 emissions. Five variants of RDFs were developed on the basis of commercial solid waste compositions. Results revealed that RDF variation 3 comprising 20% paper and 80% plastics exhibits the highest energy of 6272 kcal/kg. As preliminary study, cement industry Y is investigated as an example. During the simulation of the clinker production, RDF variation 3 is combined with petroleum coke, coal, fuel oil, or natural gas. Compared to other fuels, the combination of petroleum coke and RDF variation 3 exhibits the best CO2 reduction of 2, 155.3 106 Kt CO2/year, with the total annual clinker production of 12.64 million tons. These findings should aid policy and decision makers of waste management service provision and industry to design financially viable management systems based on resource recovery options.

Enzyme activity of waste activated sludge extracts.

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.

Comprehensive Understandings of Rare Earth Element (REE) Speciation in Coal Fly Ashes and Implication for REE Extractability.

In recent years, recovery of rare earth elements (REEs) from coal fly ashes (CFAs) has been considered as a promising resource recovery option. Yet, quantitative information on REE speciation in CFAs and its correlation with REE extractability are not well established. This study systematically investigated the REE speciation-extractability relationship in four representative CFA samples by employing multiple analytical and spectroscopic techniques across the micro to bulk scale and in combination with thermodynamic calculations. A range of REE-bearing phases are identified, such as REE oxides, REE phosphates, apatite, zircon, and REE-bearing glass phase. REEs can occur as discrete particles, as particles encapsulated in the glass phase, or distribute throughout the glass phase. Although certain discrepancies exist on the REE speciation quantified by X-ray adsorption spectroscopy and acid leaching due to intrinsic limitations of each method, both approaches show significant fractions of REE oxides, REE phosphates, apatite, and REE-bearing Fe oxides. This study contributes to an in-depth understanding of the REE speciation-distribution-extractability relationship in CFAs and can help identify uncertainties associated with the quantification of REE speciation. It also provides a general methodology for future studies on REE speciation in complex environmental samples and a knowledge basis for the development of effective REE recovery techniques.

In-vessel co-composting – a rapid resource recovery option for septage treatment in Indian cities

Abstract Septage management is a challenging task across India as more than 44% of the population depends on septic tanks for human waste management. Septage collected from Chennai city, India, was found to be rich in nutrients even though the total solids content (&amp;lt;2%) and C/N are low. The current practice of septage disposal in Chennai city is co-treatment in existing sewage treatment plants. The main drawback of this method is that treatment efficiency could deteriorate if the organic load increased much beyond the design load of the treatment plant and would result in poor treated-water quality. In this context, the present study focused on the potential of in-vessel co-composting as a sustainable treatment option. In order to enhance the co-composting process, suitable co-substrates were identified for making the process efficient and cost-effective. The area under the temperature profile during composting was used as an assessment tool for the identification of the proper mix. Addition of mixed organic waste and coir pith waste (bulking agent) to the dewatered septage gave the highest area among the different combinations. Different waste combinations were investigated in order to assess the suitability for field scale application.

Operating parameters for three resource recovery options from slow-pyrolysis of faecal sludge

Abstract Slow-pyrolysis is a treatment technology that is being explored for treatment of faecal sludge (FS) from onsite sanitation technologies. Next to pathogen inactivation, the technology produces treatment products. Revenues from these products could offset treatment costs and contribute to financially viable sanitation. In comparison to lignocellulosic biomass and other biowastes, little information is available on operating parameters for FS pyrolysis to produce char for different resource recovery options. In Kampala, Uganda, this bench-scale study investigated the influence of two major operating parameters, hold time (10, 20 and 40 minutes) and pyrolysis temperature (350, 450 and 600 °C) for pyrolysis of FS into char for solid fuel production, soil enhancement and carbon sequestration. Hold time: 10 min was the most suitable hold time for all resource recovery options as char characteristics had only minor variations between hold times. Temperature: Char characteristics identified 350 °C as the most suitable for fuel production and 450 or 600 °C for carbon sequestration. FS char had characteristics for soil enhancement comparable to biowaste and lignocellulosic biomass chars, with heavy metal concentration exceeding guideline concentrations. The most suitable temperature needs to be selected based on plant and soil type, and legal regulations.

Chemical characterization of faecal sludge in the Kumasi metropolis, Ghana

Background: Faecal sludge (FS) represents a huge resource, which when tapped and made use properly can be of great benefit to many. However, the key to tapping this resource lies in proper characterisation, in order to make known the constituents and thereby determine the end-use. Methods: Three sources of FS from 43 communities in the Kumasi metropolis of Ghana were characterised in terms of their total solids content, chemical oxygen demand (COD), pH, nitrogen, phosphorous and lipid contents. FS from pit latrines, public septage and private septage were analysed. Results: On average, lipid content was found to be in the range of 8.82 – 9.66% of dry FS depending on the source of FS. Total solids were between 0.79 and 4.68%, while the COD was between 9495 and 45611mg/L. Phosphorus content was in the range of 137 – 520mg/L, while nitrogen was 649 – 4479mg/L. Most FS samples were generally alkaline in nature. Conclusions: These results are amongst the first long-term characterization efforts for FS in terms of conventional and non-conventional characteristics, tailored towards typical treatment and novel resource recovery options, respectively.