Method For Sewage Sludge Treatment Research Articles

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.

In-situ Cu-loaded sludge biochar catalysts for oxidative degradation of bisphenol A from high-salinity wastewater

Safe disposal of excess sewage sludge (SS) produced from chemical/biochemical water treatment processes has been a worldwide concern. In this work, sewage sludge biochar-based Cu-loaded catalysts (CSBC) were synthesized by a simple impregnation-pyrolysis method. The impregnated Cu2+ in SS was converted to Cu0/CuI species after pyrolysis, which greatly improved the removal efficiency of bisphenol A (BPA). BPA (100 mg/L) could be completely removed within 130 min in CSBC/Peroxydisulfate (PDS) system, compared to 77.8% in sewage sludge biochar/PDS system. Meanwhile, CSBC performed well over a wide pH range of 3∼9. In CSBC/PDS system, singlet oxygen (1O2) dominated non-radical pathway had been proved to play an essential role in BPA degradation, boosting the oxidative treatment of phenolic wastewater under high-salinity. Results showed that the removal efficiency of BPA reached 93.6%, 91.0% and 84.6% in high-salinity wastewater with salinities of 16, 80, and 160 g/L, respectively. The total estimated cost of CSBC (1 kg) was $5.053 and the cost of BPA-containing wastewater (100 mg/L) treatment was estimated approximately 0.02 $/L, indicating its cost-effectively potential in practical applications. This study not only provides a new value-added reuse method for sewage sludge treatment and disposal, but also a new strategy for the effective treatment of high-salinity organic wastewater.

An economic and global warming impact assessment of common sewage sludge treatment processes in North America

This study details a probabilistic life cycle assessment model to evaluate the environmental (i.e., global warming potential) and economic impact of four common sewage sludge treatment methods (anaerobic digestion, incineration, composting and pyrolysis) coupled with their most common end-of-life scenarios for the North American context. The model is subsequently applied to a realistic case study where each technology is assessed over a 10-year analysis period based on data made available by a Canadian municipality. For the case study, pyrolysis and anaerobic digestion coupled with agricultural land application have an expected global warming impact at least 46% and 60% lower, respectively, than the alternative treatment methods. Conversely, composting and pyrolysis have an expected life cycle cost at least 32% and 27% lower, respectively, than the competing treatment alternatives. Composting is able to achieve its relatively low life-cycle costs through the affordability of the required capital investments; conversely, pyrolysis is able to reduce its life-cycle cost through the recovery of valuable resources such as energy, fertilizer, and fuel. These findings and the resulting tool from this work will aid decision-makers as they seek sustainable sewage sludge treatment strategies.

Comparative life-cycle assessment of pyrolysis processes for producing bio-oil, biochar, and activated carbon from sewage sludge

This study aimed to determine the feasibility of pyrolysis scenarios as sewage sludge treatment processes through cradle-to-gate life-cycle assessment and additional energy consumption, carbon emission, and economic benefit analyses, considering circular economy principles. The examined pyrolysis scenarios include slow pyrolysis with various residence times to produce activated carbon (AC) or biochar and fast pyrolysis to produce bio-oil, all with internal gas energy recovery. The functional unit (FU) in this study comprises 1000 kg of dried sludge entering the pyrolysis reactor. The overall evaluation and new product application routes address gaps in current studies on sludge treatment via pyrolysis. Environmentally, the bio-oil (-0.31 kg CO2-eq/kg FU) and biochar (-0.05 kg CO2-eq/kg FU) scenarios show considerable improvement over contemporary pyrolysis and other conventional sludge treatment methods. The AC scenarios have higher toxicity but lower carbon emissions (1.50–1.70 kg CO2-eq/kg FU) than contemporary AC production processes. Chemical reagent usage has significant effects on the environmental burden of AC production processes. The biochar and bio-oil pyrolysis scenarios achieve net energy recovery through product applications. Although the AC scenarios still require energy input, this demand can be significantly reduced by optimising moisture removal processes. Operating cost analysis indicates that the examined pyrolysis scenarios are potentially profitable. Primary product yield and market value are significant factors determining the net profit of these pyrolysis scenarios, but further assessment of capital costs is required. This study shows that bio-oil and biochar pyrolysis are eco-friendly sewage sludge treatment methods.

Short-Chain Fatty Acids Production from Anaerobic Fermentation of Sewage Sludge: The Effect of Higher Levels Polyaluminium Chloride.

With the annual increase in the sludge production in China’s sewage treatment plants, the problem of sewage sludge treatment and disposal is becoming more and more serious. Anaerobic fermentation can convert complex organic matter in sewage sludge into short-chain fatty acid, hydrogen, methane and other resources and is an effective method for sewage sludge treatment and disposal. At the same time, sewage sludge often contains flocculants, which will inevitably affect the effect of anaerobic fermentation. As a high-performance flocculant, polyaluminum chloride (PAC) is widely used in wastewater treatment and sewage sludge dewatering processes. Previous studies indicated that lower levels of PAC inhibit the effect of the anaerobic fermentation process of sewage sludge; on the other hand, it is necessary to understand the effects of higher levels of PAC in anaerobically fermented sewage sludge. The results showed that higher levels (0.2–1 g Al/g total solids (TS)) of PAC could promote acid production from anaerobically fermented sewage sludge. Moreover, mechanism studies suggest that higher levels (0.2–1 g Al/g total solids (TS)) of PAC caused excessive adsorption of the charge on the surface of the sewage sludge colloid and reversed the charge. The sewage sludge colloid was stabilized again, which increases the concentration of soluble proteins, polysaccharides, and soluble extracellular polymers (S-EPS) in the fermentation broth, thereby improving the anaerobically fermented sewage sludge efficiency. The results provided from this study may act as technical reference and guidance for the engineering application of sewage sludge anaerobic fermentation.

Сорбционная очистка осадков сточных вод от тяжелых металлов

Introduction. Because of urban development the volume of municipal and industrial wastewater are growing. Along with them the amount of sewage sludge (SS) also increases. Millions of tons of SS are currently accumulated on the territory of the Russian Federation and contain various pollutants, including heavy metals (HM). In this regard, the search for effective methods of SS treatment from HM is an urgent problem. The main methods of SS treatment are drying, dehydration, thermal methods, UV and microwave wave treatment. These kinds of disinfection eliminates many pathogenic microorganisms, but they are quite expensive and not effective against HM. Reagent methods include SS disinfection with quicklime (CaO). However, decontamination requires large doses (up to 30%) and it is also ineffective against HM. Humic-mineral reagent are more effective, they are based on crushed caustobiolites, their cleaning capacity from HM is 19–87%. Methods and materials. The authors have previously shown the effectiveness of wastewater treatment from HM using sorbents based on dolomite, quartzite, and waste from mining and processing plants. Therefore, a method for SS treatment from HM using sorbents based on dolomite, humates, and CS containing CaCO3 and humic compounds was proposed. In this regard, a method was proposed for SS treatment from HM using three types of sorbents based on: 1) waste of thermal power plants (TPP) – conditioned sludge (CS) containing CaCO3 up to 68% and humic compounds up to 12% – sorbent 1 (S1); 2) dolomite – Mg and Ca carbonate in a composition with sodium humate (25%)– sorbent 2 (S2); 3) modified dolomite with sodium humate (1%) – sorbent 3 (S3). Results and discussion. In laboratory experiments, the cleaning capacity of SS was studied using a dolomite-based sorbent modified with humate (1%). In field tests, a decrease in the concentration of HM in SS was studied with the use of sorbents based on CS and the complex sorbent dolomite-humate (75:25). The cleaning capacity of SS from HM increases in the series: sorbents based on waste from TPP – CS containing CaCO3 and humates (cleaning capacity E = 4.8–48.6% for dried SS and 29.3–53.3% for dehydrated SS) < sorbent based on a composition of dolomite with humate (E = 65.1–92.1% for dried and 56.6–89.4% for dehydrated SS) < a dolomite-based sorbent modified with humate (E = 90.8–99.9%). Conclusions. The maximum cleaning capacity is shown by a dolomite-based sorbent coated with a nano- and micro- sized layer of sodium humate.

Role of feedstock properties and hydrothermal carbonization conditions on fuel properties of sewage sludge-derived hydrochar using multiple linear regression technique

Hydrothermal carbonization (HTC) has emerged as a promising method for sewage sludge treatment. It is important to understand how process conditions (i.e. temperature, duration, and HTC reaction severity) and feedstock properties affect the product characteristics, which has been examined statistically using multiple linear regression (MLR) technique in this study. Good agreement has been observed between the results from the analysis of variance (ANOVA) and those reported by the experiments. The fuel properties of hydrochar were affected by the characteristics of raw sludge on different statistical significance. The HTC reaction severity combining with HTC duration or temperature was deemed statistically significant for hydrogen, oxygen, nitrogen, volatile matters and ash contents in the hydorchar, while HTC duration and HTC temperature were of statistical significance to sulfur and fixed carbon contents, respectively. However, carbon content in the hydrochar was only statistically dependent on the initial sludge properties. Subsequently, MLR models were developed based on ANOVA results, suggesting that these models fitted the data associated with hydrochar properties well in terms of correlation coefficiency >0.8 and root mean squared error of calibration <3%. Meanwhile, all these developed models could reasonably predict the fuel properties of hydrochar, whose values were within 10% of the corresponding experimental values. Thus, they can be adopted as a general guide or a screening tool to meet specific carbonization objective.

Life cycle environmental impacts of sewage sludge treatment methods for resource recovery considering ecotoxicity of heavy metals and pharmaceutical and personal care products

Sewage sludge handling is becoming a concern in Europe due to its increasing amount and the presence of contaminants, such as heavy metals and pharmaceutical and personal care products (PPCPs). Currently, over 70% of sludge in Europe is treated thermally by incineration or used as fertilizer in agriculture. New thermochemical methods are under development and are expected to be implemented in the near future. This paper considers the life cycle environmental impacts of the following five alternatives for sludge handling, taking into account the presence of heavy metals and PPCPs: i) agricultural application of anaerobically digested sludge; ii) agricultural application of composted sludge; iii) incineration; iv) pyrolysis; and v) wet air oxidation. The results suggest that anaerobic digestion with recovery of nutrients and electricity has the lowest environmental impacts in 11 out of 18 categories considered. For the mean to maximum resource recovery, composting is the worst alternative, followed by pyrolysis with lower recovery rates. Agricultural application of anaerobically digested sludge has the highest freshwater ecotoxicity due to heavy metals, unless their concentration is in the lowest range, as found in some European sewage sludge applied on land. Therefore, stricter control of heavy metals in the sludge is needed for this option to limit freshwater ecotoxicity to the levels comparable with the thermal processes. The results also indicate that PPCPs have a negligible contribution to freshwater ecotoxicity when compared to heavy metals in the anaerobically digested sludge. Since thermal processes are currently drawing attention due to their potential benefits, the findings of this work suggest that their adoption is environmentally beneficial only if high resource recovery rates can be achieved.

Feasibility of alternative sewage sludge treatment methods from a lifecycle assessment (LCA) perspective

Abstract Sewage sludge treatment and disposal are critical global issues, with concerns including sludge volume/weight, release of pollutants, and other environmental impacts. This study develops a semi-quantitative assessment methodology for selecting appropriate sludge treatment options on the basis of a lifecycle assessment approach. Various biological, chemical, thermal, and thermo-chemical sludge treatment methods described in the literature are reviewed and evaluated holistically by adopting the developed methodology to determine their comparative effectiveness in reducing sludge volume/weight and environmental impacts. Anaerobic digestion, pyrolysis, and supercritical water oxidation are found to be the best-performing treatment methods. They are not only more effective in reducing sludge volume/weight and pollutants but also have lower global warming and toxicity potential compared to most of the other methods reviewed. The potential for adverse environmental effects remains owing to the release of pollutants when the products of sludge treatment are utilised, e.g. as soil amendments or fuel. This necessitates further investigation to explore the toxicity impacts of a wider array of emerging pollutants from a lifecycle perspective as well as further development of sludge treatment methods to overcome the drawbacks of existing methods.

A two-step process for sewage sludge treatment: Hydrothermal treatment of sludge and catalytic hydrothermal gasification of its derived liquid

The worldwide increase in amount of sewage sludge has recently attracted considerable interest in developing an efficient and economical sludge disposal method. A sewage sludge treatment process combining the hydrothermal treatment (HT) of sludge and the catalytic hydrothermal gasification (CHTG) of its derived liquid (HT&CHTG-Process) is proposed in this paper. Liquid hourly space velocity (LHSV) value of 25–100 h−1 and liquid flow rate of 10–40 mL/min were employed with a self-designed CHTG experimental setup. During the first stage of the HT-Process, approximately 56% of the carbon in the sludge was transferred into the derived liquid at 300 °C. During the second stage of the CHTG-Process, the derived liquid was gasified into CH4, H2, and CO2 using a Ni/carbon catalyst, and the carbon conversion reached 88% at 350 °C and 20 MPa with a LHSV of 25 h−1. Using the integrated HT&CHGT-Process, approximately 0.78 Nm3 of CH4, 0.62 Nm3 of H2 and 0.31 Nm3 of CO2 were generated from 1 kg of carbon in the sewage sludge. The combined process was expected to be an efficient method for sewage sludge treatment due to its mild conditions (≤350 °C and ≤20 MPa) and high yield of fuel gases.

Greenhouse gas emissions from different sewage sludge treatment methods in north

Abstract The most sustainable method for treating sewage sludge depends strongly on the situation and local circumstances. In sparsely populated northerly areas are demanding boundary conditions, e.g. cold and long winter, long transport distances and low amounts of generated sludge. In this study, commonly used calculators and emissions coefficients for calculating the greenhouse gas (GHG) emissions from sewage sludge treatment methods were assessed to create a calculator suitable for the Northern Finland context. The calculator was then used to determine which sewage sludge treatment method (composting, anaerobic digestion (AD), incineration (with and without thermal drying)) resulted in the lowest emissions of the GHG gases in different situations in Northern Finland. GHG gases included carbon dioxide (CO2; including biobased), methane (CH4) and nitrous oxide (N2O), measured as carbon dioxide equivalents (CO2eq). According to the calculator, AD generated the least CO2eq emissions of all treatment methods studied. The second best option was incineration of sludge without thermal drying, while the third best was composting or incineration of sludge after thermal drying with e.g. fossil or other fuels. Most of the emissions were generated from the treatment process itself and the share of emissions generated during transport was minimal, despite the long transport distances when all CO2 emissions (incl. biobased) were considered. The role of users of the end-products and the possibility to use the CO2 generated were highly important when considering environmental perspective. These results can be utilised when selecting the locally most suitable method. In future, some of the treatment methods (i.e. AD, incineration) with CO2 capture could be considered carbon sinks, as they also remove biobased CO2 emissions.

Co-liquefaction of sewage sludge and oil-tea-cake in supercritical methanol: yield of bio-oil, immobilization and risk assessment of heavy metals

In this study, attention was concentrated on the yields of bio-oil and toxicities of heavy metals (HMs) in liquefaction residues (LRs). Liquefaction of sewage sludge (SS) or oil-tea-cake (OTC) or mixtures of SS and OTC were carried out under the condition of supercritical methanol (SCM). Results showed that the addition of OTC extraordinarily increased the yields of oil from 37.9% (SS) to 86.2% (SS + OTC). Furthermore, with the liquefaction of SS and OTC mixture, the bioavailable fraction (F1 + F2) of Cd and Cu (F1 + F2) was decreased from 2.47 to 1.64 mg/kg and from 98.84 to 67.48 mg/kg, respectively. However, the bioavailable fraction of Zn (F1 + F2) increased from 122.03 to 204.69 mg/kg with the liquefaction of SS. The bioavailable fraction (F1 + F2) of Pb in LRs was 0%, which did not express any changes during the liquefaction process. Risk assessments of geo-accumulation index (Igeo), risk assessment code (RAC) and modified potential ecological risk index (MRI) were applied to evaluate the bioavailabilities, the potential ecological risks and the pollution levels of HMs. The results show that the OTC in SS can decrease the risk of HMs in LRs. Cd attracted many concerns for the highest risk to the environment among all of the HMs. Here, the good results obtained means that SCM liquefaction of mixture of SS and OTC could be a preferable method for SS treatment.

INFLUENCE OF BIOLOGICAL AND THERMAL TRANSFORMED SEWAGE SLUDGE APPLICATION ON MANGANESE CONTENT IN PLANTS AND SOIL

A great variety of sewage sludge treatment methods, due to the agent (chemical, biological, thermal) leads to the formation of varying ‘products’ properties, including the content of

ESBL-producing E. coli in Austrian sewage sludge

The aim of this study was to investigate the degree of contamination of sewage sludge with ESBL-producing Escherichia coli strains and the effectiveness of different sewage sludge treatment methods. Monthly sewage sludge samples were collected between January and September 2009 in 5 different sewage treatment plants and tested for the presence of ESBL E. coli. In addition, the number of colony forming units (CFU) of E. coli and coliform bacteria before and after the different sludge treatment methods (aerobic/anaerobic digestion, lime stabilization, and thermal treatment) was investigated. Of the 72 sewage sludge samples investigated, ESBL-positive E. coli were found in 44 (61.1%) sewage sludge samples. The classification of β-lactamase groups was carried out in 15 strains resulting in the detection of 2 different groups (CTX-M and TEM) of bla genes. All 15 of them had a CTX-M gene and 4 of these strains furthermore carried a TEM gene. With regard to the CFU of E. coli and coliform bacteria, thermal treatment and lime stabilization following dehydration sufficiently reduced pathogen concentrations. The plants using merely stabilization and dehydration showed an increase of E. coli and coliform bacteria and thus also an increase in ESBL-producing E. coli.

Production of a Producer Gas with High Heating Values and Less Tar from Dried Sewage Sludge through Air Gasification Using a Two-Stage Gasifier and Activated Carbon

The production of sewage sludge in South Korea is continually increasing. Until now, much of the sewage sludge in the country has been disposed of by dumping it into the ocean, which the London Convention wants stopped. Therefore, new sewage sludge treatment methods should be sought. Sewage sludge can be energetically utilized through gasification, which produces combustible gases such as H2, CO, and CH4. During the gasification of a biomass, however, a large amount of tar is also formed. In this paper we report the results of the experiments that were conducted on the air gasification of dried sewage sludge in a newly developed two-stage gasifier. In such experiments, activated carbon was applied to reduce the tar components of the producer gas. The total amount of tar that was reduced was 6-fold when activated carbon was used in the upper reactor of the gasifier. The effects of the reaction conditions, such as the reaction temperature and the equivalence ratio, on the gas composition were also investiga...

Adaptation of Betula schmidtii Seedling in Coal-mine Field with Different Sewage Sludge Treatment Methods

We tested the field adaptation of Betula schmidtii on the abandoned coal-mine soil with sludge amendment methods for promoting physiological activity of B. schmidtii seedlings under several environmental stress. Sewage sludges were amended to coal-mine soil with B. schmidtii seedlings which grown in the mixture of artificial soil and composted sludge soil before transplanting (before-fertilized treatment, BF) and fertilized with composted sludge after transplanting (after-fertilized treatment, AF). The percent of establishment of seedlings for AF (80.7%) was lower than that for BF (92.7%). Nitrate reductase activity and photosynthetic pigment content were higher in AF than in BF, but malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were lower in AF than in BF These results represent that after-fertilized seedlings increase resistance against physiological stress at field condition using nitrogen source of composted sludge. On the contrary, before-fertilized seedlings were susceptible to environmental stress on abandoned coal-mine soil by exhausting of nitrogen source from composted sludge.

Microwave-induced drying, pyrolysis and gasification (MWDPG) of sewage sludge: Vitrification of the solid residue

A novel method for sewage sludge treatment based on subjecting the wet sludge to high temperature thermal treatment in a microwave is being investigated at INCAR. Under the appropriate operating conditions, drying, pyrolysis and gasification of the sewage sludge take place, giving rise to a gas with a high CO and H 2 content and an oil with a low PAH content. Moreover, due to the high temperatures that can be attained during the process it is possible to obtain a solid residue which is partially vitrified. Unlike other methods aimed at maximizing the porous texture of the solid residue in order to produce adsorbents, the aim of the method proposed in this work is to obtain a solid residue with minimal porous textural development, where the heavy metals present in the residue are occluded in a glassy-like matrix. The advantages of this technique are a substantial volume reduction with respect to the initial sludge and a solid residue that is more resistant to the leaching of organic substances and heavy metals than the char obtained by conventional pyrolysis.