Sludge Treatment Research Articles

More Biosurfactants and Fewer Synthetic Surfactants to Improve Alkali-Surfactant-Polymer Flooding: Feasibility Study and Large-Scale Field Application

Summary Alkali-surfactant-polymer (ASP) flooding has achieved highly enhanced oil recovery (EOR) in the Daqing Oil Field; however, there are concerns about synthetic surfactants owing to their high cost and difficulty in biodegradation. Cheap biosurfactants conform to human concepts of green circular economy; however, known biosurfactants, as well as their mixtures with alkali, cannot reduce water/oil interfacial tension (IFT) to ultralow values below 0.01 mN/m, which is necessary for ASP flooding to effectively mobilize residual oil. Therefore, we investigate the feasibility of partially replacing synthetic surfactants with biosurfactants rather than completely replacing them to improve ASP flooding. First, through a series of IFT tests, a blend of rhamnolipids (RLs) and alkylbenzene sulfonate (ABS) in a 1:1 mass ratio is determined to be the optimal mixed surfactant and labeled RL/ABS-opt. Second, the interfacial activities, phase behaviors, and wettability alteration capabilities of ASP solutions with RL/ABS-opt are studied. Then, 1.0 wt% NaOH and 0.2 wt% RL/ABS-opt are determined to construct a new ASP system. Subsequently, the waterflooded cores are displaced using the new and the classical ASP systems. Based on the promising experimental results, the new ASP system floods a test block of 56 wells for 3 years. The EOR and surfactant costs are calculated to determine the technical and economic effects. Finally, the concentrations of surfactants before and after activated sludge treatment (AST) are tested by spectrophotometry to verify the biodegradability of RLs better than that of ABS. The laboratory and field results indicate that more biosurfactants and fewer synthetic surfactants could improve ASP flooding to be more environmentally friendly and cost-effective with a higher EOR.

Comparative life cycle assessment of excreta management systems through composting and biomethanization: Case of a low-income tropical country.

Low-income tropical regions, such as Haiti, grapple with environmental issues stemming from inadequate sanitation infrastructure for fecal sludge management. This study scrutinizes on-site sanitation systems in these regions, evaluating their environmental impacts and pinpointing improvement opportunities. The focus is specifically on systems integrating excreta valorization through composting and/or anaerobic digestion. Each system encompasses toilet access, evacuation, and sludge treatment. A comparative life cycle assessment was undertaken, with the functional unit managing one ton of excreta in Haiti over a year. Six scenarios representing autonomous sanitation systems were devised by combining three toilet types (container-based toilets (CBTs), ventilated improved pit (VIP) latrines, and flush toilets (WC)) with two sludge treatment processes (composting and biomethanization). Biodigester-based systems exhibited 1.05 times higher sanitary impacts and 1.03 times higher ecosystem impacts than those with composters. Among toilet types, CBTs had the lowest impacts, followed by VIP latrines, with WCs having the highest impacts. On average, WC scenarios were 3.85 times more impactful than VIP latrines and 4.04 times more impactful than those with CBTs regarding human health impact. Critical variables identified include the use of toilet paper, wood shavings, greenhouse gas emissions, and construction materials.

Comparative life cycle assessment of landfill sludge treatment technologies in China.

Reasonable treatment of large amounts of sludge excavated from landfills has gained increasing attention due to the diminishing availability of landfill space in China. In this study, five landfill sludge (LS) treatment technologies using life cycle assessment (LCA) and life cycle cost (LCC) were investigated, i.e., co-incineration in coal-fired power plants (CFPP) and waste incineration power plant (WIPP), co-processing in cement kiln, bricks production, and sintering ceramsite. The LCA results demonstrate that sintering ceramsite outperforms other technologies and LCC results indicate sintering ceramsite also provides the highest economic benefit ($869.94). To further enhance environmental and economic performances of the LS treatment, the substitution of coal with natural gas and biomass can reduce Energy Conservation and Emission Reduction (ECER) index by 74% and 98%, respectively. This substitution can increase economic returns by 24% and 26%, respectively. Furthermore, national-level economic benefit and carbon emission reduction potential of different LS treatment technology alternative scenarios were assessed. Results display that a combination of 50% CFPP, 25% bricks, and 25% ceramsite (biomass) offers the highest economic gain, which is 3.02 times that of 50% CFPP and 50% cement (original case). Conversely, the replacement of 25% brick with 25% cement in the above combination result in the lowest carbon reduction, which is 9.35 times that of the original case.

Carbon performance analysis of upgraded wastewater treatment plants in key control areas of the Ziya River Basin in China

Wastewater treatment plants (WWTPs) are one of the largest sources of greenhouse gas (GHG) emissions, and they are also one of the largest energy consumption industries in urban systems. With the progression of upgrading and standard-rising, WWTPs both directly and indirectly increase carbon emissions from the increased investments in facilities and usages in electricity as well as chemical agents. Here, we collected operational data from 15 WWTPs in the key control areas of the Ziya River Basin in North China and accounted for the changes in carbon performance at different technical upgrade methods. Results showed that the average carbon emission performance increased by 0.487 kg CO2/m3 after the upgrade. Carbon emissions from electricity consumption, chemical usage, biochemical process and sludge treatment accounted for 42%, 17%, 24%, and 17% of the total improvement in carbon emission performance, respectively. Reducing energy consumption, regulating chemical use and sludge comprehensive utilization are the key to carbon emission reduction. It further proposes that the development of wastewater treatment discharge standards should fully consider the comprehensive utilization of water quality classification. Regions with favorable natural conditions should make full use of their advantages by adopting economically feasible, low-energy-consuming technologies such as constructed wetlands, which offer carbon sequestration and landscaping benefits. This study provides guidance on the selection of technological pathways for pollution reduction and carbon mitigation in the wastewater treatment industry and on achieving sustainable water resource utilization.

Catalytic supercritical water gasification of oily sludge with the FeOOH/AC for hydrogen production

Along with the continuous increase of crude oil consumption in China, the production of oily sludge is increasing. The traditional oily sludge treatment technology cannot realize the purpose of green and efficient resource utilization of oily sludge. Supercritical water gasification hydrogen technology can efficiently convert oily sludge into hydrogen and realize the resource utilization of oily sludge. However, the traditional supercritical water gasification process requires high energy consumption. It is necessary to study the catalysts in the gasification process. Loaded catalysts have a large specific surface area and can effectively reduce the reaction activation energy. This paper investigated the effects of different catalyst types and concentrations on gasification. The results showed that adding FeOOH/AC effectively increased hydrogen production, and the best catalytic effect was achieved when the FeOOH loading was 10 wt%. The catalyst concentration was 5%, with a hydrogen production rate of 4.638 mol/kg. It was found that the activation energy of the reaction with the addition of the catalyst was reduced by 8.61 kJ/mol compared to that without the catalyst through kinetic analysis. 8.61 kJ/mol.

Life cycle assessment of sewage sludge treatment and disposal technologies based on carbon emissions and environmental impacts

ABSTRACT This study aimed to create a comprehensive evaluation method for sewage sludge (SS) treatment and disposal technologies, considering carbon emission and environmental impacts. Life cycle assessment (LCA) were conducted on six SS treatment and disposal technologies in China. The assessments used the IPCC emission factor approach to calculate carbon emissions and the CML2001 method to determine environmental impact factors. Additionally, a colour-coded method was implemented to quantify the evaluation results. The study found that S1 (anaerobic digestion + land application) had the lowest carbon emissions and environmental impact, making it the optimal technology. The S1 scenario had carbon emissions of 669 kg CO2(t DS)−1 and environmental impacts of 5.20E-10. A sensitivity analysis was conducted to show the impacts of each unit in the six technologies on total carbon emissions and environmental impacts. The results showed that landfilling has a high sensitivity to carbon emissions and environmental impacts. Therefore, controlling greenhouse gases and toxic substances in sludge landfills is crucial for reducing carbon emissions and environmental pollution.

Automatic Control of Polymer Dosage Using Floc Images in Sludge Dewatering Plant

This study introduces a novel method for estimating floc conditions in sludge dewatering plants by employing image analysis and automatic control of polymer dosage. While previous research has focused on drinking water treatment plants, few reports address polymer dosage optimization using image analysis in sludge dewatering plants. The challenge lies in the high sludge dry solids hindering individual floc recognition due to overlap. The study aims to estimate floc conditions by focusing on gap areas between flocs and implementing automatic polymer dosage control accordingly. The proposed method uses images from an Internet Protocol camera and semantic segmentation to identify the floc gap area. For validation of the estimation method, variations of over and under polymer dosage scenarios were investigated and compared with commonly used floc area methods. The findings indicate that the gap area estimation effectively reproduces the theory of polymer cohesion. Automatic polymer dosage control based on this method demonstrates stable operation in both scenarios. Notably, automatic control outperformed manual operation during continuous operation, resulting in a significant reduction in polymer dosage and a notable increase in heating efficiency compared to manual control. This study presents an efficient approach to optimize polymer dosage in sludge dewatering plants, utilizing image analysis for real-time monitoring and control. By focusing on the gap area between flocs, the method enhances accuracy in estimating floc conditions, thereby improving overall dewatering efficiency. The findings highlight the practical benefits of implementing automatic control systems in sludge treatment plants, potentially reducing costs and environmental impact.

Physicochemical characterization of wastewater from the Niamey National Hospital (NNH) (Niger) and assessment of its impact on the environment

The Niamey National Hospital (NNH) is among the reference hospital in the Niamey region (Niger) to after the quality of care it offers to the population. However, these activities have a negative impact on the quality of the water of the river constituting one of the main sources of water supply for the population of Niamey and gardening activities. This study aims to determine the physicochemical quality of wastewater from the NNH activated sludge treatment plant and its impact on the environment. To carry out this study, twenty (20) wastewater samples were taken at the outlet of the NNH treatment station. The sampling lasted five (5) weeks to take into count fluctuations. The results obtained indicate that the average values of physicochemical parameters such as: the pH (6,91), temperature (27.825°C), conductivity (574.80 µS/cm) and certain heavy metals of this hospital are compliance with national and international standards for wastewater discharge. However, it was noted that the average values ​​obtained at the HNN for copper (1.982 mg/L); zinc (1.077 mg/L); in phosphorus (18.065 mg/L); DCO (808 mgO2/L) and DBO5 (442.5 mgO2/L) do not comply with national and international wastewater discharge standards. These abnormal levels must be treated before being released into the river.

Research on Resource Recovery and Disposal of Copper-Containing Sludge.

Copper-containing sludge is a common by-product of industrial activities, particularly electroplating and metal processing. This type of sludge contains high concentrations of heavy metals such as copper, which can pose a potential threat to the environment. Therefore, its treatment and disposal require special attention. Due to its efficient mass and heat transfer characteristics, the suspended state technology has shown significant potential for application in a number of key processes, including the drying, decomposition, and reduction of copper-containing sludge. This paper presents an in-depth analysis of the current status of the application of the suspended state technology in the treatment of copper-containing sludge. Based on this analysis, a device for the treatment of copper-containing sludge in the suspended state was designed, through which the characteristics of copper-containing sludge in the oxidative decomposition and reduction phases are investigated. The research objects were gas concentration, temperature, contact state, and particle size time. Orthogonal experiments were initially employed to investigate the relationship between the influencing factors and the conversion rate of copper oxides. This was followed by a single-factor influence study, which led to the determination of the optimal process parameters for the decomposition experiments of the Cu-containing sludge in an oxidizing atmosphere. The 100 μm Cu-containing sludge was reacted with 10% O2 gas at a flow rate of 1 m/s for 3 min under the condition of 900 °C. The process parameters were then determined as follows: The research objects were gas concentration, temperature, contact state, and particle size time. Orthogonal experiments were employed to investigate the relationship between the influencing factors and the copper conversion rate. This was followed by a single-factor influence study, which determined the optimal process parameters for the copper-containing sludge reduction experiments. The 200 μm copper-containing sludge was reacted for 5 min at a flow rate of 7% carbon monoxide at a flow rate of 1.5 m/s under the condition of 800 °C.

Uptake of tire-derived compounds in leafy vegetables and implications for human dietary exposure

IntroductionTire and road wear particles are one of the most abundant types of microplastic entering the environment. The toxicity of tire and road wear particles has been linked to their organic additives and associated transformation products. Tire and road wear particles, and associated tire-derived compounds are introduced to the agricultural environment via atmospheric deposition, irrigation with reclaimed wastewater, and the use of biosolids (treated sewage sludge) as fertilizer. In the agricultural environment, these tire-derived compounds could be taken up by edible plants, leading to human exposure.MethodsSixteen tire-derived compounds were measured in twenty-eight commercial leafy vegetable samples from four countries. Based on the results, the estimated daily intake of these tire-derived compounds was calculated due to leafy vegetable consumption based on local diets under a mean and maximum concentration scenario.ResultsIn commercial leafy vegetables, six tire-derived compounds were detected: benzothiazole (maximum concentration—238 ng/g dry weight), 2-hydroxybenzothiazole (maximum concentration—665 ng/g dry weight), 1,3-diphenylguanidine (maximum concentration—2.1 ng/g dry weight), N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD, maximum concentration—0.4 ng/g dry weight), N-Isopropyl-N-phenyl-4-phenylenediamine (IPPD, maximum concentration—0.1 ng/g dry weight), and N-phenyl-N-cyclohexyl-p-phenylenediamine (CPPD, maximum concentration—0.3 ng/g dry weight). At least one compound was present in 71% of samples analyzed. The estimated daily intake for 1,3-diphenylguanidine ranged from 0.05 ng/person/day in the mean scenario to 4.0 ng/person/day in the maximum scenario; benzothiazole ranged from 12 to 1,296 ng/person/day; 6PPD ranged from 0.06 to 2.6 ng/person/day; IPPD ranged from 0.04 to 1.1 ng/person/day; CPPD ranged from 0.05 to 2.6 ng/person/day.DiscussionStatistical analyses did not reveal correlation between known growth conditions and tire-derived compound concentrations in the leafy vegetable samples. The estimated daily intake via leafy vegetable consumption was generally lower than or comparable to the estimated daily intake via other known sources. However, we show that tire-derived compounds are taken up by foodstuff, and exposure might be higher for other produce. Future studies are needed to uncover pathways of tire-derived compounds from road to food, assess the exposure to transformation products, and investigate the biological effects associated with this exposure.

Environmental and economic analysis of the transformation of paper mill sludge treatment technologies in China.

Paper mill sludge (PMS) is featured with a high content of cellulose and hemicellulose, and using its characteristics to make paperboard can achieve a high-value utilization of PMS, which has attracted growing interest. In this study, currently prevalent landfill, incineration technologies (generating heat and electricity by incineration), and three paperboard technologies (medium density fiberboard, pulp board, and corrugated paper) were evaluated and compared via life cycle assessment (LCA) and life cycle costing (LCC) methods. LCA results show that the PMS-to-pulp board outperforms others with an energy conservation and emission reduction (ECER) value of - 2.86 × 10-8, while the landfill exhibits the highest overall environmental impact with an ECER value of 4.80 × 10-9. LCC results reveal that the PMS-to-pulp board delivers the highest economic profit with $257.357, while the landfill is the lowest with $ - 35.63. The PMS paperboard technologies are more economically friendly than the incineration technologies due to additional electricity/steam consumption during the PMS pre-drying process in incineration. In addition, different scenarios were set up to explore national GHG emission reduction potential by increasing paperboard technologies application rate and reducing the proportion of landfill and incineration. The scenario analysis suggests that replacing 90% of landfill and incineration ratio with PMS paperboard technologies could tremendously improve the overall emission reduction performance with - 9.08 × 1010 kg CO2 eq. This result indicates that the PMS treatment technology transformation has a significant favorable impact on the achievement of the "carbon neutrality" target.

Wastewater Treatment Sludge and Agricultural Wastes: Management by Composting Process

This study aimed to investigate the compostability of wastewater treatment sludge and evaluate the effects on compost quality of adding cotton gin waste and peanut shell. For this purpose, treatment sludge was mixed with cotton gin waste in the ratios of 60:40 in M1 reactor and 80:20 in M2 reactor, while in M3 and M4 reactors, treatment sludge was mixed with peanut shell in the same proportions. The highest temperatures were reached in reactors M2 (65.2 °C) and M4 (68.7 °C) where 80% treatment sludge was added. These reactors also experienced the highest organic matter losses of 42.2% and 31.5%, respectively. It can be stated that a faster microbial decomposition and stabilization occurred in these reactors. It can be said that the composting process may be a preferable method for the management of treatment sludge and agricultural wastes. Furthermore, the outcomes of the study can serve the food industry and agriculture sector through effective bioconversion of organic waste.Graphical

Natural deep eutectic solvents pretreatments for sludge dewaterability improvement and subsequent volatile fatty acids production: Insights of sludge disintegration and metagenomic characterization

Higher economic returns and carbon–neutral benefits drive research shifting to volatile fatty acids (VFAs) recovery from sludge treatment. The novel natural deep eutectic solvents (NADES) based pretreatments of waste activated sludge (WAS) were proposed, focusing on sludge dewaterability, organics dissolution, and subsequent production of VFAs via anaerobic fermentation. Three different pretreatment methods, i.e., NADES treatment alone, NADES with 80 °C thermal treatment, and NADES with 180 °C hydrothermal treatment were systematically compared. The dewaterability of sludge significantly improved only when NADES assisted by thermal treatments, which was interpreted by a substantial decline in capillary suction time (CST) and water-holding capacity. All three pretreatments boosted the VFAs production from sludge (1.40–2.33 times compared with control), and increased the proportion of acetic acid by about 10%. Results showed that the highest VFAs yield of 2728.71 mg COD/L was obtained from NADES combined with 180 °C hydrothermal treatment, which was increased by 133 % compared with the control. Such performance is much higher than a surfactant assisted hydrothermal treatment recently reported in the literature (increased by 27 %). Mechanistic studies elucidated that NADES stimulated sludge solubilization, enhancing the release of organic substrates for VFAs production. Further metagenomic analysis demonstrated that the hydrolytic-acidogenic bacteria were enriched after NADES treatments. Moreover, glycosyl transferases (GTs) and carbohydrate esterases (CEs) were the primary carbohydrate-active enzymes (CAZymes) enhanced by NADES addition. This study provides new insights into green solvents simultaneously enhanced sludge dewatering and resource recovery.

The durability of slag and tannery sludge based geopolymer corroded by acid and base solutions

The current treatment (landfill, composting, and incineration) of chromium-containing sludge can contaminate soil, surface water and groundwater. In this study, tannery sludge and granulated blast furnace slag was chosen to make a geopolymer and its ability to resist acid and alkali was investigated by immersing them in different solutions for 28 d. The experimental results showed that when pH value increased from 1.0 to 13.0, the compressive strength linearly increased from 36.7 MPa to 68.4 MPa while the porosity decreased from 4.37 % to 3.4 %. The results of NMR, SEM and FIR showed that the H+ in HCl acid solution depolymerized the three-dimensional network structure of the geopolymer and acicular product (CaCl2) was generated, which leaded to the increase in small pores and large pores. However, when immersed in alkaline solution the secondary polymerization occurred and more C-S-H appeared, making the geopolymer denser. In addition, the environmental benefits of the geopolymer were investigated and the results showed that the leaching concentration ranges of total chromium and Cr(VI) were 1.21–0.97 mg/L and 0.04–0.06 mg/L, both of which were far below the requirement of standards. The CO2 emission was 8.06 kg/(m3 Mpa), which was roughly half of the ordinary Portland cement (18 kg/(m³ MPa)). Therefore, the geopolymer could be a way to treat tannery sludge and the geopolymer made of tannery sludge and slag had the potential to be environmentally friendly building materials.

Mutual-benefit modification of the coagulant solution and fly ash for enhanced sludge dewatering

Faced with the escalating volume of municipal sludge from wastewater treatment plants, urgent measures are required to enhance the sludge dewatering efficiency. This study introduces an innovative and cost-effective approach for mutual modifications of AlCl3 coagulant solution (AC) and fly ash (FA) powder as additives to significantly enhance sludge dewaterability. Unlike the traditional method that modifies agents alone, our technique achieves dual functionalities via blending FA with AC at room temperature. The modified FA (MFA) exhibits a 60 % increase in specific surface area to 2.176 m2/g and ζ-potential shift from –22.2 to +2.0 mV, meanwhile enhances the metal ions content in the modified AC (MAC) by dissolving 96.5 % of Ca, 70.3 % of Mg, 10.6 % of Fe, and 6.1 % of Al ions from FA. When sludge is treated with 5 % MAC and 10 % MFA, the water content in the filter cake is reduced from 84.9 % originally to 52.9 % through plate-frame pressure filtration (PFPF), a significant improvement over 65.4 % for that with unmodified AC and FA treatment, corresponding to the decreased specific resistance to filtration (SRF) and increased the filtration flux during the draining phase. The notable dewaterability enhancement through AC and FA modification is due to the enhanced flocculation and charge neutralization by the abundant metal ions in MAC, coupled with the MFA-facilitated water adsorption and drainage channel maintenance. This one-step, double-benefit modification not only surpasses traditional methods in dewatering efficiency but also reduces sludge treatment costs by 42.4 %, offering a sustainable solution to the increasing challenges of municipal sludge management.

Migration of trace elements and radioisotopes to various fractions of solid wastes generated as a result of the sewage sludge incineration process

The research was aimed at providing new knowledge in the field of chemical characteristics of solid waste generated in the process of combustion of sewage sludge in fluidized bed furnaces. The research material consisted of disposed fluidized beds (DFB), sewage sludge ash (SSA) and air pollution control residues (APC) from three Polish installations for the thermal treatment of sewage sludge. Natural radionuclides as well as anthropogenic isotope 137Cs were determined in the tested materials and the migration of a wide spectrum of trace elements to various waste fractions generated in the process of sewage sludge combustion was examined. It was observed that both radioisotopes and most of the trace elements determined accumulate in SSA and DFB, while the APC fraction contains a much smaller amount of them. The exceptions are mercury and selenium, whose volatile compounds migrate to the exhaust gas dedusting system and accumulate in the APC fraction (up to 40 mg/kg and 13 mg/kg, respectively). A potential threat from the 226Ra isotope in SSA is identified in the context of the management of this waste in the production of building materials because the typical activity of 226Ra in SSA collected from areas with very low Ra content in natural environment exceeds 1.5–6 times the activity of this isotope in conventional cement mixtures. When managing SSA and DFB, special attention should be paid to the content of metalloids such as As, B and Se, due to the high content of mobile forms of these elements in the mentioned materials.

Utilization of durian peels (Durio zibethinus) and lubricant treatment sludge as raw materials of Refuse-Derived Fuel

Fossil energy is among the most widely utilized energy sources in Indonesian industry, but its continuous use is leading to its depleted. Refuse-derived fuel (RDF) offers an alternative made from organic and inorganic waste. Durian peel is identified as a promising raw material for RDF due to its high calorific value of 6,274 Kcal/kg. Additionally, Lubricant Treatment Sludge (LTS), which is collected from the oil treatment industry, is used to enhance RDF’s calorific value, as it contains residual oil rich in hydrocarbons. To bind the RDF components, tapioca starch, durian seeds, and rejected papaya were selected as adhesives. The mixture ratios of durian skin, LTS, and adhesive were tested at compositions (90:0:10), (85:5:10), (80:10:10), (75:15:10), and (70:20:10). Subsequent RDF characteristics analyses included tests for moisture content, ash content, volatile matter, fixed carbon, and calorific value. Based on these evaluations, the most optimal composition was determined to be 90% durian peel, 0% LTS, and 10% tapioca starch adhesive. This composition exhibited a moisture content of 1.6%, volatile matter of 74.6%, ash content of 8.4%, fixed carbon of 15.2%, and a calorific value of 3,516 Kcal/kg. Tapioca starch emerged as preferred adhesive due to its favorable properties and characteristics.

Dehydration and Environmentally Friendly Thermal Processing of Excess Activated Sludge

Introduction. Currently, there is a problem with the accumulation of large amounts of production waste. One type of this waste is excess activated sludge, which is a waste product from biological wastewater treatment that has a high moisture content. When excess activated sludge is deposited in beds, problems can arise related to changes in the gas-air environment, the release of unpleasant odors, as well as the contamination of groundwater and soil. Prolonged presence of sediment in sludge beds in oxygen-free conditions leads to its decay and deterioration of moisture-yielding properties. For these reasons, the development of new methods for disposing of large volumes of waste generated during wastewater treatment is essential. The aim of this research is to develop a technique for preliminary neutralization and thermal treatment of excess activated sludge using energy waste. Materials and Methods. The work used excess activated sludge with a moisture content of 98.2% (waste of hazard class IV). Water treatment sludge (waste of hazard class V) was used as a reagent to increase moisture yield. For experimental studies on dehydration, a laboratory centrifuge Elmi CM-6M.01 was used. Tests were conducted under various conditions (500, 1 000, and 1 500 revolutions per second for 1, 2, and 3 minutes), and the value of centrifugation was determined as a criterion for moisture yield in the sludge. Fuel pellets were produced by rolling with technical lignosulfonate as a binding agent. Elemental analysis of the samples was conducted to study the possibility of thermal treatment using an EA 3 000 Euro Vector Analyzer. Results. A comprehensive technology has been developed to clean the resulting gas emissions from solid particles formed during the combustion of fuel pellets and remove them from the furnace in the form of fly ash along with the outgoing gases. This technology also removed sulfur oxides, nitrogen oxides, and polychlorinated dibenzodioxins and dibenzofurans, while beneficially utilizing flue gas heat by reducing its temperature from 900–1 200°C to 140°C. Discussion and Conclusion. The approach proposed in this article for the processing and disposal of large volumes of waste allows for the reduction of moisture content of excess activated sludge and the use of this waste as a secondary energy source. This method is environmentally friendly and addresses both technical and environmental challenges, such as the effective recycling of industrial waste and reducing the anthropogenic impact on soil, air, and groundwater. It also provides an opportunity to generate additional electrical and thermal energy through thermal utilization of waste. The results of this work indicate that it is possible to integrate the use of various types of industrial waste (sewage sludge, water treatment waste, and pulp and paper industry waste) as secondary energy sources. These findings have practical implications for enterprises in both the municipal and industrial sectors with wastewater treatment facilities.

Enhancing Sewage Sludge Treatment with Hydrothermal Processing: A Case Study of Adana City

As a byproduct of municipal wastewater treatment systems, sewage sludge has traditionally been treated in low-value applications such as landfilling, posing significant environmental risks due to its pollutant content. However, there is a growing interest in utilizing the energy potential of sewage sludge through thermochemical conversion methods. Among these methods, hydrothermal liquefaction (HTL) has come to the fore as a promising green approach, offering an environmentally friendly means of extracting bio-oils and biochemicals from sewage sludge. In this study, the HTL method, regarded as an innovative approach among sewage sludge treatment methods apart from incineration, pyrolysis, and landfilling, is comparatively investigated in terms of greenhouse gas (GHG) emissions alongside other methods. In particular, this study analyzes the projected amount and various characteristics of sewage sludge that could potentially be generated by 2030 for the city of Adana, which currently produces approximately 185 tons of sewage sludge per day. The findings indicate that without intervention, sludge production is projected to reach 68,897 tons per year by 2030. Moreover, this research demonstrates that the utilization of HTL for sludge treatment results in a reduction of emissions by approximately 7-fold compared with incineration of sewage sludge.

Septic tank usage and its faecal sludge management in Cuenca, Ecuador

ABSTRACT On-site sanitation systems such as septic tanks are widely used for treating domestic wastewater in urban and rural areas which lack sewage systems. However, a large portion of these systems do not properly treat human excreta. A main challenge to improve this is the absence of comprehensive data regarding the usage, emptying and maintenance. In this study, records of septic tank desludging frequency during 2009–2022 and the sewerage coverage updated to 2022 were used to investigate their spatial and temporal utilisation, and the persistence of septic tank usage in areas with sewer networks and uncover the current state of Faecal Sludge Management in Cuenca, Ecuador. The spatial behaviour revealed that OSSs are still in use besides the presence of a sewer network. In 2022, there were 109 septic tanks in urban areas with 14.7% in sectors with sewerage service. In rural areas, 469 septic tanks were recorded with 7.8% situated in areas with sewer networks. Although there is no specialised infrastructure in place for the treatment and disposal of faecal sludge, the city has effectively managed it with the existing sanitation facilities. This assessment contributes to the formulation of a secure framework for a safely managed sanitation.