Sewage Sludge Generation Research Articles

Improved biohydrogen production using Ni/ZrxCeyO2 loaded on foam reactor through steam gasification of sewage sludge

The pervasive generation of sewage sludge (SES) and deficiencies in its disposal methods have resulted in several significant environmental and human health challenges. This study explored the catalytic effect of nickel (Ni)-based CeO2, ZrO2, Zr0.8Ce0.2O2, Zr0.4Ce0.6O2, and γ-Al2O3 supports in fixed beds and foam reactors in the steam gasification of SES. A comparison of the hydrogen selectivity and gas yield of the synthesized catalysts confirmed that the metal composite support, especially Zr0.8Ce0.2O2, had a positive effect on the catalytic activity and stability. This can be attributed to the enhanced oxygen vacancies and oxygen mobility, resistance to coke deposition, uniform morphology, improved dispersion, and increased number of Ni sites on the Zr0.8Ce0.2O2 support. Furthermore, foam reactors offer unique advantages in improving hydrogen production. This study provides an advanced strategy for SES valorization that fulfills the requirements of an economically and environmentally sustainable technology.

Production strategies and potential repercussion of sewage sludge biochar as a futuristic paradigm toward environmental beneficiation: A comprehensive review

AbstractThe generation of sewage wastewater is unavoidable due to the continual increase in the global population that paves the way to appropriate disposal management. Sewage wastewater treatment and consequent generation of sewage sludge (SS) are well connected with global environmental issues. Upon risk assessment on different SS disposal methods, converting SS into biochar, that is, sewage sludge biochar, can be recommendable management. It is well‐proven for excellent positive impacts, such as nutrient enhancement, and healthier plant growth, and mitigates the emissions of greenhouse gases while amending with agricultural soil. However, the outcome features of SSB significantly vary with pyrolysis temperature and its elemental constituents. In addition, many studies revealed that the process temperature is key to responsible for the desirable properties and functioning of SSB. In this context, many countries support to the development of a futuristic strategy for SS management toward producing SSB and its utilization in agriculture. This review compiles studies into SSB's ability to promote a sustainable effect on the total worldwide output volume. Furthermore, the generation of SSB is also analyzed from a socioeconomic standpoint in relation to other common SS disposal management strategies.

Life cycle assessment: Sustainability of biodiesel production from black soldier fly larvae feeding on thermally pre-treated sewage sludge under a tropical country setting

More energy is needed nowadays due to global population growth. Concurrently, sewage sludge generation has also increased steadily stemming from the inevitable urbanization. As such, black soldier fly larvae (BSFL) can be potentially deployed to solve both issues. This paper investigates the environmental sustainability of biodiesel production derived from sludge-fed BSFL feedstock. A cradle-to-gate life cycle assessment (LCA) was performed through SimaPro software utilizing the ReCiPe 2016 Midpoint (H) and Endpoint (H) methods. The entire LCA covered 3 main stages, including the thermal pre-treatment of sludge, BSFL rearing and processing, and lastly lipid extraction and biodiesel production. LCA showed that the sludge pre-treatment stage had the highest environmental impact, while BSFL rearing and processing had the least due to the suitable geographical climate. Electricity usage during the pre-treatment stage was the main contributing component, followed by chemical usage during biodiesel production. After normalizing, it was observed that land occupation, marine ecotoxicity, freshwater ecotoxicity and freshwater eutrophication were more impactful than the commonly studied global warming potential (GWP). Lipid content and biodiesel conversion efficiency were determined as the sensitive factors which could influence the LCA outcome. In comparison with other types of biodiesel, BSFL biodiesel had a milder impact in terms of climate change, land occupation, terrestrial acidification, marine and freshwater eutrophication. Furthermore, this biological reduction of sludge through BSFL valorization avoided sludge landfilling, which reduced up to 100 times GWP. Therefore, sludge-fed BSFL biodiesel production is an environmentally-sound and highly potential solution that should be investigated comprehensively.

Production of low carbon dioxide cement containing sewage sludge ash as mineral admixture

Cement is an essential construction ingredient, and the demand for it has increased multifold during the last couple of years due to various construction activities. For the manufacturing of cement, limestone is a key component, which is a major source of carbon dioxide (CO2) emission. Moreover, municipalities all over the world have long been concerned about the disposal of sewage sludge. Due to increased generation of sewage sludge, urgent alternative solutions are required for sludge disposal, one of which is recycling of waste into construction materials. In accordance with the concept of sustainability, low carbon dioxide cement is produced in the current study by blending sewage sludge ash (SSA) and carbide lime sludge (CLS) (industrial waste) with ordinary Portland cement (OPC). In terms of physical properties, the influence of low carbon dioxide cement containing different percentages of SSA with 10% CLS is compared with that of composite cement containing fly ash at different percentages with 10% CLS. The outcome from the study shows that the utilization of OPC blended with up to 45% SSA with CLS would be possible, as it results in an acceptable level of compressive strength, conservation of depleting limestone reserves, savings in thermal and electrical energy and reduction of carbon dioxide emissions.

Experimental analysis of strength and durability properties of cement binders and mortars with addition of microfine sewage sludge ash (SSA) particles

Generation of sewage sludge is increasing all over the world, and its safe disposal is becoming a serious concern. Utilization of this waste as a raw material for some products can lead to multiple advantages. Considering the physical and chemical properties of the sludge, it can be used as a replacement for cement as its properties are similar to those of cement. Moreover, the sludge is being incinerated for better workability. The purpose of this study is to utilize supplementary cementitious materials like sewage sludge ash as a replacement for cement for better properties like strength and durability. Incorporating such waste materials into concrete can reduce the use of cement, making it eco-friendly. During this investigation, the water-cement ratio was kept constant at 0.5. Different percentages (5,10,15,20,25) of microfine Sewage Sludge Ash (SSA) a being used as a replacement for the cement. Tests conducted during this analysis are compressive; setting time, rapid chloride permeable test (RCPT) and XRD (for the detection of the occurrence of crystalline material). The results show that the compressive strength of the mortar at 10% is higher than that of 20%. Cement binders and mortars could benefit from the usage of this waste material because it has a significant impact on their strength and durability.

Investigation in Techniques for Using Sewage Sludge as an Energy Feedstock: Poland’s Experience

The sludge generated from wastewater treatment facilities contains high nutrients and is characterized by high heating values. Thus, the sludge enriched with organic matter and nutrients is a potential candidate for its application as fertilizers and an alternate energy feedstock. Nowadays, energy independence contributes to the economic stability of the country, and therefore the search for alternate energy sources is an acute issue. This paper presents a case study on using sewage sludge as an energy feedstock in Poland. The physicochemical characteristics of the sewage sludge are presented. The fuel properties of sewage sludge generated from different waste water treatment plant (WWTP) are summarized. The calorific value of sewage sludge generated in Poland is insufficient for effective use as an energy raw material, therefore, energy potential of mixture of sludge with other waste have been studied. The general trend of sewage sludge formation and the quantitative forecast for the future showed that in 2020, compared to 2012, sludge accumulation increased by 6.9%, but compared to 2019 - decreased by 3%. From 2012 to 2020 the average, sewage sludge accumulation increased annually by 0.8%. This demonstrates the heterogeneity of waste streams for the production of alternative fuels and a modest increase in sewage sludge production in the coming years. This made it possible to prepare several options for the further development of research in the field of developing technologies for obtaining alternative energy. Also this study will help the prospective researchers understand sewage sludge generation and its use as energy feedstock.

Comparative Life Cycle Assessment Analysis of Sewage Sludge Recycling Systems in China

With the acceleration of economic development and urbanization in China, sewage sludge generation has sharply increased. To maximize energy regeneration and resource recovery, it is crucial to analyze the environmental impact and sustainability of different sewage sludge recycling systems based on life cycle assessment. This study analyzed four sewage sludge recycling systems in China through life cycle assessment using the ReCipe method, namely aerobic composting, anaerobic digestion and biomass utilization, incineration, and heat utilization and using for building materials. In particular, the key pollution processes and pollutants in sewage sludge recycling systems were analyzed. The results demonstrated that aerobic composting is the most environmentally optimal scenario for reducing emissions and energy consumption. The lowest environmental impact and operating costs were achieved by making bricks and using them as building materials; this was the optimal scenario for sludge treatment and recycling. In contrast, incineration and heat utilization had the highest impact on health and marine toxicity. Anaerobic digestion and biomass utilization had the highest impact on climate change, terrestrial acidification, photochemical oxidant formation, and particulate matter formation. In the future, policy designers should prioritize building material creation for sludge treatment and recycling.

Evaluation of the Pozzolanic Activity of Uncontrolled-Combusted Sewage Sludge Ash

Waste management is a crucial issue facing modern society. The generation of sewage sludge is increasing annually due to the urbanization and improvement of sanitation systems of cities. The construction sector has emerged as a solution for the elimination of waste due to the enormous volume of materials that this sector can absorb. This paper evaluates the pozzolanic activity of sewage sludge ash (USSA) obtained following an uncontrolled-combustion process, a simple and economic procedure. Compressive strength of Portland cement/USSA mortars with 5%–25% by weight USSA were evaluated. Calcium hydroxide/USSA and Portland cement/USSA pastes were chemically and physically characterized through thermogravimetric/differential-thermogravimetric (TG/DTG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. The increase in the replacement of Portland cement by USSA is associated with an increase in the compressive strength of mortars. These values for USSA containing mortars cured for 90 days were in the range of 49.6–55.4 MPa, higher than the one reached by the reference mortar. According to the microstructural analysis, the increment on the compressive strength can be attributed to the formation of hydrated products (C─ S─ H, C─ A─ S─ H, and C─ A─ H) by the pozzolanic reaction of USSA.

Waste to Catalyst: Synthesis of Catalysts from Sewage Sludge of the Mining, Steel, and Petroleum Industries

The generation of sewage sludge presents a problem for several manufacturing companies as it results from industrial processes or effluent treatment systems. The treatment of this type of waste requires high economic investment, for this reason, it is necessary to find alternatives to recover the valuable materials of the sludges. In this study, metal catalysts were synthesized using waste sludge from the steel, mining, and hydrocarbon industries. The waste sludge was subjected to thermal treatments for the removal of organic content and the reduction of metals with hydrogen current to activate their catalytic properties. The sludge and synthesized catalysts were analyzed to determine their physical, chemical, thermoenergetic, and catalytic properties. Catalytic activity was evaluated using CO chemisorption and by thermal–catalytic decomposition of crude oil. The best conditions for synthesizing the catalysts were a calcination temperature between 300 and 500 °C and a reduction temperature between 300 and 900 °C. The catalysts presented a specific surface between 2.33 and 16.78 m2/g. The catalytic material had a heat capacity between 0.7 and 1.2 kJ/kg∙K. The synthesized materials presented catalytic activity comparable to that of commercial catalysts. With this recovery technique, the industrial waste can be valorized, obtaining catalyst derived from the sludges and promoting the circular economy of manufacturing companies.

Nutritional evaluation of Guanandi seedlings fertilized with sewage sludge

The generation of sewage sludge and the concern with their fate has greatly increased. The objective of this study was to assess the effects of using in natura (SS) or composted sewage sludge (SSC) in comparison with mineral fertilizer (MF) application and a control (CT) treatment on the nutritional status of Guanandi (Calophyllum brasiliense Cambess.) seedlings in a typical Red Oxisol in Brazil. The leaf-level nutritional responses of the Guanandi seedlings to these three different fertilizers and the control were evaluated at 90 and 180 days after planting. Nutritional data of leaf variables were compared between the treatments by means of one-way analysis of variance using the F test and a pair-wise comparison of means done by Tukey’s test. The seedlings that received SS or SSC showed deficiencies in Ca, Mg, and Mn, which were confirmed by a visual diagnosis of their leaf symptoms. However, at 180 days after planting there were significant differences (p < 0.05) for K that was greater for MF, SS and SSC than CT, Mg, with SSC larger than SS, and for S that was greater with SS and SSC uses relative to MF. The results highlight the potential for using SS and SSC, after adding KCl and lime, although the Guanandi was highly demanding of Ca, Mg, and Mn. However, they were able to nutritionally supply seedlings, although the short-term cannot be conclusive as regards the exclusive use of them in place of mineral fertilizers.

Gaseous emissions from sewage sludge combustion in a moving bed combustor

Substantial increase in sewage sludge generation in recent years requires suitable destination for this residue. This study evaluated the gaseous emissions generated during combustion of an aerobic sewage sludge in a pilot scale moving bed reactor. To utilize the heat generated during combustion, the exhaust gas was applied to the raw sludge drying process. The gaseous emissions were analyzed both after the combustion and drying steps. The results of the sewage sludge characterization showed the energy potential of this residue (LHV equal to 14.5MJkg−1, db) and low concentration of metals, polycyclic aromatic hydrocarbons (PAH), polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF). The concentration of CO, NOx, BTEX (benzene, toluene, ethylbenzene and xylenes) emitted from the sludge combustion process were lower than the legal limits. The overall sludge combustion and drying process showed low emissions of PCDD/PCDF (0.42ng I-TEQNm−3). BTEX and PAH emissions were not detected. Even with the high nitrogen concentration in the raw feed (5.88% db), the sludge combustion process presented NOx emissions below the legal limit, which results from the combination of appropriate feed rate (A/F ratio), excess air, and mainly the low temperature kept inside the combustion chamber. It was found that the level of CO emissions from the overall sludge process depends on the dryer operating conditions, such as the oxygen content and the drying temperature, which have to be controlled throughout the process in order to achieve low CO levels. The aerobic sewage sludge combustion process generated high SO2 concentration due to the high sulfur content (0.67wt%, db) and low calcium concentration (22.99gkg−1) found in the sludge. The high concentration of SO2 in the flue gas (4776.77mgNm−3) is the main factor inhibiting PCDD/PCDF formation. Further changes are needed in the pilot plant scheme to reduce SO2 and particulate matter emissions, such as the installation of exhaust gas-cleaning systems. According to previous studies, the efficient operation of such cleaning systems is also effective for metals emission control, which makes the combustion of sewage sludge a feasible treatment method from both energetic and environmental perspectives.

Future sewage sludge generation and sewer pipeline extension in economically developing ASEAN countries

Levels of future generation of sewage sludge must be ascertained to ensure safe and effective waste management, particularly for economically developing countries such as those of the Association of Southeast Asian Nations (ASEAN), where wastewater treatment will increase profoundly in the near future. This study estimated the quantity of sewage sludge generation in ASEAN during 2010–2050. Parameters used in the scenario analysis include population (P), per-capita gross domestic product (GDPpc), rate of population in residences connected to wastewater treatment plants (P wwtp %), and sewage sludge generation per capita (SSpc). High sewerage penetration scenarios indicate that the sewage sludge in the ASEAN countries is expected to increase to 24–40 million tonnes per annum (Mt/a) by 2050. Indonesia might contribute the greatest amount of 17.04 Mt/a at mid-century, followed by the Philippines and Vietnam. Because of its small population, Brunei Darussalam will contribute the least. Sewage pipeline length has also been estimated. High-penetration scenarios indicate that the sewer network in ASEAN will surge to 2.3–7 million km long. Because sewage sludge management and development of wastewater infrastructure will play important roles in the ASEAN region, these findings will be informative for wastewater management policies and practices in Southeast Asia.

The Reuse of Sewage Sludge: Current Problems and Future Trends

In all likelihood, the management of solid and liquid wastes will become one of the most important environmental problems of the 21st Century. A major priority is thus to develop new strategies for the reduction, reuse, recycling, and valorization of this waste in order to reduce its negative impact on the environment. European Union countries are currently required to treat urban wastewater in all the cities, and consequently a significant increase in the generation of sewage sludge has been produced. However, the toxic substances in this kind of sludge have created a new environmental problem. Composting is an aerobic process, during which organic waste is biologically degraded by microorganisms to humus-like material. The microbiota and its physico-chemical changes during the composting process have received much attention during the last years. In this context, different culture dependent and culture independent techniques have been used to describe the constant and shifting biodiversity present in the composting process. In this paper several aspects related to sewage sludge are analyzed: origin, composition and microbial structure. Moreover, the use of sludge to produce biofuels is also reviewed as a novel biotechnology. Keywords: Sewage sludge, sludge reuse, composting, bacterial diversity, third-generation biofuels, viable seeds, PLFA, SSCP, DGGE, TGGE, heavy metals, secondary sludge, mixed sludge, aerobic digestion, anaerobic digestion.

Sewage Sludge: An Important Biological Resource for Sustainable Agriculture and Its Environmental Implications

Intensive farming generally needs large addition of organic matter to maintain fertility and enhance crop yields. Sewage sludge/biosolids are by-products of municipal and industrial wastewater treatment and a rich source of organic nutrients. Sewage sludge having high content of organic matter, macro- and micro-nutrients, can be used as fertilizer/soil conditioner for food, vegetable crop, horticultural plants and pasture, which in most cases can be beneficially recycled. In the past sewage sludge was regarded as a waste product due to expected high level of contaminants such as pathogens, pollutants and synthetic materials discharged in sewer from homes and industries, which were often incinerated, dumped in occasion or land fill. As a result of rapidly increasing population, urbanization and industrialization, wastewater production and sewage sludge generation have increased manifold. Due to high cost of mineral fertilizers and escalating trends in their prices, there is an increasing trend of using sewage sludge in agriculture, especially under intensive cropping in arid and semi arid regions of the country. Therefore, application of sewage sludge to agricultural soils may be sustainable and economical due to nutrient cycling and disposal of sewage sludge. However, there may be a risk in use of sewage sludge due to potentially harmful contents present in the sludge such as heavy metals and pathogens. This paper, therefore, presents a review on various aspects of sewage sludge used in agriculture.

The preparation of an adsorbent from mixtures of sewage sludge and coal-tar pitch using an alkaline hydroxide activation agent

The increasing generation of sewage sludge and its subsequent treatment are very sensitive environmental problems. For the more stable and sanitary treatment of this sewage sludge, there have been many studies, including the recent attempt to prepare an adsorbent from sewage sludge via recycling. In this study, of the adsorbent preparation methods, chemical activation was utilized, and in order to find the optimum conditions, several variables were tested, such as the activation agent concentration, activation temperature and activation time. The activation agents used in this study were alkaline hydroxides: KOH and NaOH. The properties of prepared adsorbent were also measured by analyzing the iodine adsorptivity and surface area. In addition, the prepared adsorbent, the BOD, COD, SS, T-N and T-P removal efficiencies from the effluent water of a sewage treatment plant were examined via column test. From the test, the optimum conditions for KOH-activation were 1 mol/l, 800 °C and 1.5 h for the activation agent concentration, activation temperature and activation time, respectively; whereas those for NaOH-activation were 1.25 mol/l, 850 °C and 1.5 h. From the application of the prepared adsorbent to the effluent water of the sewage treatment plant, the measured BOD, COD, SS, T-N and T-P removal efficiencies, the P1-800 adsorbent had the highest efficiencies for BOD, COD and SS of 56.68, 57.76 and 81.45%, respectively.

A Study on Producing Refuse Derived Fuel (RDF) Using Waste Plastic Film and Sewage Sludge: - The usability of Raw Materials for RDF -

To ascertain the possibility of producing refuse derived fuel (RDF) using waste plastic film and sewage sludge, the current state of waste plastic film and sewage sludge generation was investigated and the heavy metal components and heating values for those materials were analyzed. At this time waste plastic film from agricultural production is being discarded in the fields and sewage sludge is being buried in landfills or discharged into the ocean, resulting in land and ocean pollution in Korea. Waste plastic film from mulching operations on farm land and sewage sludge could be used to produce RDF if they are mixed in the proper ratio to get the heating value required for standard RDF. The Hg, Cd, Pb and As content did not exceed the specified limits for RDF, demonstrating the usability of waste plastic film and sewage sludge as raw materials of RDF. From an elementary analysis of waste plastic film and sewage sludge, SO2 gas is not expected to be discharged, while NOx gas may possibly be discharged in the flue. To get the heating value required for RDF, a mixture of 50% waste plastic film and 50% sewage sludge was desirable.

The stabilization of sewage sludge by pulverized fuel ash and related materials

In Hong Kong, with the implementation of the Strategic Sewage Disposal Strategy (SSDS), there will be a substantial increase in the generation of sewage sludge. An alternative method using pulverized fuel ash (PFA) generated from a local coal fire power station and lime to stabilize the sludge for potential beneficial uses is studied. The effects of the stabilizing agents on the leaching of heavy metals and pasturing of coliform are studied. The results show that PFA together with a small percentage of lime addition has the potential to reduce heavy metal leaching and reduce the total coliform content of the stabilized sewage sludge.

A CLOSED WATER REUSE SYSTEM FOR POWER PLANT COOLING AND DIGESTER HEATING1

ABSTRACT: A model consisting of closed water reuse and productive use of various types of wastes for energy generation is presented. The sewage after treatment would be used as the cooling water for power plants, and the condenser discharge therefrom be used as heating water for sludge digesters. The water is then purified for municipal water supply for continuous use. The advantages of this system are that water resources and energy are conserved while various types of wastes including waste heat are controlled.With a preliminary system analysis, it appears that the design for power plant based on the total heating value of wastes and digester capacity based on sewage sludge generation is feasible in terms of acquisition and full utilization of various types of wastes as generated in a single metropolitan area. The system as shown in this design is in balance among various factors such as the generation rate of municipal refuse, municipal sewage, waste heat in the condenser discharge, and raw sewage sludge.