Sludge Water Research Articles

EFFECT OF PULP SLUDGE COMPOST VS. MANURE FERTILIZER APPLICATION TO THE GROWTH OF GERONGGANG (Cratoxylum arborescens) SEEDLINGS IN PEAT SOIL

The pulp industry is crucial for Indonesia, but the waste produced should be managed. Pulp sludge contains organic matter suitable for compost material. This study examines the response of geronggang (Cratoxylum arborescens) seedlings' growth to the application of pulp sludge compost compared to commercial manure fertilizer and non-fertilized soil for six months. A fifteen kg of pulp sludge (water content of 60-70%) mixed with decomposers (Penicillium citrinum and Penicillium oxalicum (107 spores/mL)) was incubated for a month. The compost or fertilizer at a dosage of 0, 2, 4, 6, 8, 10, 12, 14, and 16 (tons/ha) was added to peat soil for the seedlings' growing media. The manure fertilizer contained higher macronutrients than the sludge compost, while the peat was considered poor soil. Seedlings with sludge compost or manure fertilizer addition at a dosage equal to 2 (tons/ha) showed the highest survival rate after six months. The sludge compost addition raised the seedling's height, diameter, and dry weight more than another treatment. The sludge compost at a dosage equal to 16 and 12 (tons/ha) significantly increased the height and diameter of the seedlings, respectively. The sludge compost has shrink-swell characteristics that are potent water retention in dry soil.

Effects of salinity and betaine addition on anaerobic granular sludge properties and microbial community succession patterns in organic saline wastewater

In this study, the effects of different salinity gradients and addition of compatible solutes on anaerobic treated effluent water qualities, sludge characteristics and microbial communities were investigated. The increase in salinity resulted in a decrease in particle size of the granular sludge, which was concentrated in the range of 0.5-1.0 mm. The content of EPS (extracellular polymeric substances) in the granular sludge gradually increased with increasing salinity and the addition of betaine (a typical compatible solute). Meanwhile, the microbial community structure was significantly affected by salinity, with high salinity reducing the diversity of bacteria. At higher salinity, Patescibacteria and Proteobacteria gradually became the dominant phylum, with relative abundance increasing to 13.53% and 12.16% at 20 g/L salinity. Desulfobacterota and its subordinate Desulfovibrio, which secrete EPS in large quantities, dominated significantly after betaine addition.Their relative abundance reached 13.65% and 7.86% at phylum level and genus level. The effect of these changes on the treated effluent was shown as the average chemical oxygen demand (COD) removal rate decreased from 82.10% to 79.71%, 78.01%, 68.51% and 64.55% when the salinity gradually increased from 2 g/L to 6, 10, 16 and 20 g/L. At the salinity of 20 g/L, average COD removal increased to 71.65% by the addition of 2 mmol/L betaine. The gradient elevated salinity and the exogenous addition of betaine played an important role in achieving stability of the anaerobic system in a highly saline environment, which provided a feasible strategy for anaerobic treatment of organic saline wastewater.

A three-stage process of Mn(VII)-Fe(III)/PDS system for enhancing sludge dewaterability: Effective driving of Fe(II)/Fe(III) cycle and adequate assurance of ROS

Sludge dewatering helps to reduce the cost of sewage treatment plants and environmental impact. Hence, we used a type of permanganate (Mn(IV)) activated ferric chloride (Fe(III))/ peroxydisulfate (PDS) system to enhance sludge dewaterability. At optimal dose, the simultaneous addition of Mn(IV), Fe(III) and PDS (MFP treatment) reduced the value of specific resistance to filtration (SRF) from 6.76 × 108 s2/g to 2.01 × 108 s2/g. There is a three-stage process during MFP conditioning: oxidation/flocculation, adsorption/oxidation, and reflocculation. X-ray photoelectron spectroscopy (XPS) and Electron spin resonance (ESR) analyses were employed to investigate the oxidation mechanism. Meanwhile, the analysis of Mn valence was improved by considering metal leaching rates. The cycles of Mn(II)/Mn(III)/Mn(IV) were initiated under the reaction between Mn(VII) and extracellular polymeric substances (EPS)/PDS. This process sustained the cycle of Fe(II)/Fe(III) to promote activation of PDS, which continuously promoted to generate OH•, SO4-•, •O2–, 1O2 and Fe(IV). Additionally, sludge EPS was proven to be the primary electron donor of Fe(II)/Fe(III) cycle, resulting in the increasing of Fe(II) proportion. Notably, the hydrophilicity and water-holding capacity of EPS declined significantly following excellent oxidation, which promoted the conversion of bound water. The effective destruction of hydrogen bonds and protein secondary structures explained the outstanding effects. Meanwhile, XDLVO calculation revealed that sludge coagulation performance enhanced through Fe(III) flocculation, MnO2 adsorption and hydrophobic flocculation. Raw and converted free water would be effectively removed through the more hydrophobic surface of large and tough drain pores formed after the reflocculation process. The efficient drainage of sludge water created strong sludge dewaterability. This study verified the practicality of MFP treatment by exploring the oxidation and coagulation mechanisms to clarify the dewatering mechanism.

Emerging progress of carbon nanomaterials in wastewater treatment: synthesis and utilization

Abstract In this work, data from experiments concerning carbon components in various forms, including graphite, graphene oxide (GO), active carbon, compilations, and analyses of the substances used as efficient wastewater management agents, are conducted. The initial phase involved characterizing the mentioned carbon compounds and nanoparticles (NPs) using various complementary methods. Raman spectrophotometry, energy-dispersive spectroscopy, scanning electron microscopy, and zeta spectrum research are involved in the approach. The next obstacle was coming up with a very straightforward procedure that would allow us to examine whether carbon NPs behaved in a mixture of effluent water and active sludge regarding hydrodynamic and physiological consequences. Principal component analysis (PCA) (univariate and multivariate) has confirmed the complicated relationships of NPs made of GO with organisms observed in processed wastewater. PCA techniques are used to evaluate experimental outcomes. Utilizing the results from this experiment, several huge-scale studies on how active NPs affect wastewater purification may be designed. Simulations using PCA clearly showed that GO significantly impacts the wastewater technical processes under investigation. It is envisaged that the discoveries will enable the design of clever conservation technologies.

A quantitative theory integrating solid surface hydrophilicity and pore structure features for non-phase-change drying of sewage sludge through gradient increase of ultrahigh filtration pressure

The sustainable application of thermal sludge drying process is limited by the high energy consumption due to the phase-change latent heat of moisture. This study proposed that the ultrahigh pressure filtration could realize the non-phase-change sludge drying. The lowest water content of 28.12 wt.% was realized by the filtration pressure of 21 MPa for the excess sludge with polyaluminium chloride as the conditioning agent. With the stepwise increase of filtration pressure employed (5-21 MPa), the diameter of solid pores was gradually narrowed to the same order of magnitude with the thickness of vicinal water film (i.e., 1-10 nm). As a result, the capillary water was transformed into the vicinal water, and the solid-water interface interaction played more crucial roles in water occurrence states. However, Hagen-Poiseuille equation was introduced to estimate the pore water outflow based on the pore wall hydrophilicity and the external filtration pressure, which implied that there can be always a sufficiently large driving force to maintain the water outflow rate no matter how the pore diameter is small and the sidewall is hydrophilic. Typically, the fitting results of excess sludge (R2=0.985, p-value<0.01) indicated that the pressure gradient of 2.11 × 109 Pa/m was required to maintain the pore water flow rate of 1.38 × 10−15 m3/s with the median pore diameter of 5.33 × 10−7 m. All these findings broke through the conventional cognition that only thermal drying process can decrease the sludge water content below 60 wt.%, and facilitated energy saving of sludge dewatering process through non-phase-change separation, i.e., ultrahigh pressure filtration.

Candidate biomarkers of antibiotic resistance for the monitoring of wastewater and the downstream environment

Urban wastewater treatment plants (UWTPs) are essential for reducing the pollutants load and protecting water bodies. However, wastewater catchment areas and UWTPs emit continuously antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs), with recognized impacts on the downstream environments. Recently, the European Commission recommended to monitor antibiotic resistance in UWTPs serving more than 100 000 population equivalents. Antibiotic resistance monitoring in environmental samples can be challenging. The expected complexity of these systems can jeopardize the interpretation capacity regarding, for instance, wastewater treatment efficiency, impacts of environmental contamination, or risks due to human exposure. Simplified monitoring frameworks will be essential for the successful implementation of analytical procedures, data analysis, and data sharing. This study aimed to test a set of biomarkers representative of ARG contamination, selected based on their frequent human association and, simultaneously, rare presence in pristine environments. In addition to the 16S rRNA gene, ten potential biomarkers (intI1, sul1, ermB, ermF, aph(3′’)-Ib, qacEΔ1, uidA, mefC, tetX, and crAssphage) were monitored in DNA extracts (n = 116) from raw wastewater, activated sludge, treated wastewater, and surface water (upstream and downstream of UWTPs) samples collected in the Czech Republic, Denmark, Israel, the Netherlands, and Portugal. Each biomarker was sensitive enough to measure decreases (on average by up to 2.5 log-units gene copy/mL) from raw wastewater to surface water, with variations in the same order of magnitude as for the 16S rRNA gene. The use of the 10 biomarkers allowed the typing of water samples whose origin or quality could be predicted in a blind test. The results show that, based on appropriate biomarkers, qPCR can be used for a cost-effective and technically accessible approach to monitoring wastewater and the downstream environment.

Metabolically Active Microbial Communities in Oilfields: A Systematic Review and Synthesis of RNA Preservation, Extraction, and Sequencing Methods

Characterizing metabolically active microorganisms using RNA-based methods is a crucial tool for monitoring and mitigating operational issues, such as oil biodegradation and biocorrosion of pipelines in the oil and gas industry. Our review, a pioneering study, addresses the main methods used to preserve, isolate, and sequence RNA from oilfield samples and describes the most abundant metabolically active genera studied. Using the MEDLINE/PubMed, PubMed Central, Scopus, and Web of Science databases, 2.561 potentially eligible records were identified. After screening, 20 studies were included in our review, underscoring the scarcity of studies related to the subject. Data were extracted and reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). These studies evaluated different samples, including produced water (PW), injection water (IW), solid deposits (SD), oil (OIL), and oily sludge (OS) collected from oilfields located in Australia, China, India, Mexico, and the United Arab Emirates. Environmental samples accounted for 55% of the studies, while enriched cultures and microbial consortia represented 35% and 15% of studies, respectively. PW was the most frequently studied sample, comprising 72% of all samples. Filtration and centrifugation were the only processes employed to concentrate the biomass present in samples. For RNA preservation, the most used method was a solution composed of 95:5 v/v ethanol/TRIzol, while for RNA isolation, the TRIzol reagent was the most cited. The Sanger sequencing method was used in all studies evaluating functional genes (alkB, dsrA, aprA, assA, and mcrA), and the Next-Generation Sequencing (NGS) method was employed in studies for sequencing transcripts of the 16S rRNA gene and metatranscriptomes. Pseudomonas (16S rRNA = PW: 2%; IW: 8%; metatranscriptome = PW: 20%) and Acinetobacter (16S rRNA = PW: 1%; IW: 4%; metatranscriptome = PW: 17%) were the most abundant genera. This study outlined the primary methods employed in researching metabolically active microorganisms. These data provide a foundation for future research. However, it is essential to note that we cannot yet determine the most effective method. We hope that this study will inspire further research related to the standardization of RNA preservation, extraction, and sequencing methods and significantly contribute to our understanding of active microbial communities in oilfields.

Improving properties of bilge water’s treatment sludge in a port reception facility by novel continuous ultrasonic reactor

ABSTRACT The main problem faced by facilities dealing with bilge water treatment is the generation of a high sludge amount, which has significant contents of oil and hazardous substances. The presence of petroleum and petroleum-derived organic oil, which ranges from 10 to 20% in bilge water with varying characteristics not only poses challenges in treating the bilge water but also complicates the management of the bilge water treatment sludge. Hence, this study aims to improve the characteristics of treatment sludge generated after bilge water treatment at one of Turkey’s largest port waste reception facilities (PRF), consisting of a combined process involving ultrasound and a filter press. When the filter press was used to reduce the water content in the sludge cake to approximately 65%, a similar water content of about 65% was achieved by employing ultrasound as a pre-treatment, even when the initial sludge contained 95–98% water. Additionally, the application of ultrasound before the filter press did not have a significant impact on the values of total organic carbon (TOC) and loss on ignition (LOI). However, the value of dissolved organic carbon (DOC) decreased by 45% when subjected to sonication for 60 minutes at a density of 100 W/L. Furthermore, when ultrasound was applied as a pre-treatment, an increase in the sonication duration resulted in improvements of 10% and 22% in the parameters of total dissolved solids (TDS) and chloride, respectively, which were influenced by different levels of ultrasonic power. Briefly, such research has been novelly conducted on the management of bilge water treatment sludge. Ultrasound, which is often preferred in sludge dewatering applications, was applied to this type of sludge for the first time, and the studies were conducted in a pilot-scale facility and a real PRF field. In conclusion, the partially promising results of this study will provide a new alternative and a pioneering guide for the treatment of bilge water sludge.

The role of ubiquitous metal ions in degradation of microplastics in hot-compressed water

Hydrothermal processing (HTP) is an efficient thermochemical technology to achieve sound treatment and resource recovery of sewage sludge (SS) in hot-compressed subcritical water. However, microplastics (MPs) and heavy metals can be problematic impurities for high-quality nutrients recovery from SS. This study initiated hydrothermal degradation of representative MPs (i.e., polyethylene (PE), polyamide (PA), polypropylene (PP)) under varied temperatures (180–300 °C) to understand the effect of four ubiquitous metal ions (i.e., Fe3+, Al3+, Cu2+, Zn2+) on MPs degradation. It was found that weight loss of all MPs in metallic reaction media was almost four times of that in water media, indicating the catalytic role of metal ions in HTP. Especially, PA degradation at 300 °C was promoted by Fe3+ and Al3+ with remarkable weight loss higher than 95% and 92%, respectively, which was ca. 160 °C lower than that in pyrolysis. Nevertheless, PE and PP were more recalcitrant polymers to be degraded under identical condition. Although higher temperature thermal hydrolysis reaction induced severe chain scission of polymers to reinforce degradation of MPs, Fe3+ and Al3+ ions demonstrated the most remarkable catalytic depolymerization of MPs via enhanced free radical dissociation rather than hydrolysis. Pyrolysis gas chromatography-mass spectrometry (Py GC–MS) was further complementarily applied with GC–MS to reveal HTP of MPs to secondary MPs and nanoplastics. This fundamental study highlights the crucial role of ubiquitous metal ions in MPs degradation in hot-compressed water. HTP could be an energy-efficient technology for effective treatment of MPs in SS with abundant Fe3+ and Al3+, which will benefit sustainable recovery of cleaner nutrients in hydrochar and value-added chemicals or monomers from MPs.

CHARACTERISATION OF Moringa Oleifera FOR PURIFICATION OF TREATED WATER SLUDGE

Proper disposal of treated water sludge is one of the main challenges water treatment Plants are facing globally. This entails disposing of sludge in such a way that it will not be harmful to the environment due to the chemicals used during the treatment of the water. The disposal of sludge conditioned by chemical polymers has an adverse effect on health and the environment. The use of natural polymers (such as wool polymer) has been explored to reduce adverse effects that come from chemical polymers (polyurethane). Elemental compositions of Moringa Oleifera were distinctive using ultimate analysis, proximate Analysis, Fourier Transform Infrared Spectroscopy, and energy-dispersive X-ray fluoresce. Characterization was done to examine the composition, functional characteristics, and physico-chemical properties of moringa oleifera . The proximate result showed that Moringa oleifera contains 36.34% of crude lipids, 3.78% of moisture,4.08% of Ash, 4.70% of crude fibre, 29.56% of crude protein, and 21.54% of carbohydrate. The ultimate result showed that carbon contains 45.86% and hydrogen has 1.96%. FTIR Spectrum of Moringa Oleifera showed C≡N(carbon-nitrogen) C=N and S-S (Sulphur-Sulphur) stretching bond. FT-IR spectra showed the presence of protein and lipids components. The FTIR Spectrum of the dry sludge showed many vibrations indicating some functional groups like N-H in Amides, alcohols and amines O-H, (Oxygen-hydrogen) C≡C bond C=N, C-H(Carbon -Hydrogen)O-CH3, P-N-C, C-H in aldehydes and acids C=O in Carboxylic acids, and S-S bond ED-XRF showed the elemental composition of Moringa Oleifera; 0.018% Fe, 0.001% Cu, 0.003% Al 9.00%, 0.038% Mg etc. and that of the dry sludge as 9.22%, Fe2O3, 0.572% CuO, 9.63% Aluminum oxide, 29.96% Silicon Oxide, 2.57% magnesium oxide. Turbidity of the treated sample was reduced to the level of Nigerian standard (5NTU). Moringa Oleifera was discovered to be a viable and affordable alternative for conditioning of water treatment sludge.

Enhancing data reliability in quantitative characterization of moisture distribution in sludge using DSC: Impact of sample attributes and test parameters

Exploring moisture distribution, especially bound water content, is vital for studying and applying sludge dewatering. The differential scanning calorimetry (DSC) method has been extensively utilized for the quantitative characterization of moisture distribution in sludge. However, this method has certain limitations, such as low reproducibility of results, leading to controversial parameter values in different papers and hindering result comparison. In this study, we investigated the influence of key sample attributes on measuring sludge bound water using the DSC method.The findings demonstrated that the moisture content and mass of sludge samples substantially influenced the reproducibility and stability of DSC test results. To ensure data reliability, the moisture content of the sludge sample should be minimized and kept below 84%, with the mass not exceeding 10 mg. Compared to the influence of sludge moisture content and sample mass, the heating rate (1⁓5 °C/min) minimally affected DSC test results. This study offers a comprehensive insight into how sample attributes and test parameters affect the quantitative characterization of bound water in sludge using the DSC method. Furthermore, practical strategies are presented to enhance the method's applicability in sludge bound water characterization.

In-situ utilization of EPS improves the directional oxidation ability of Fe(III)/H2O2 and enhances sludge dewaterability

Inefficient sludge dewatering can result in high costs for sludge treatment and disposal, as well as increased pollution of the environment. In this study, we constructed a double oxidation–reduction (Redox) cycle system of Fe(II)/Fe(III) and Fe(II)-extracellular polymeric substance (EPS)/Fe(III)-EPS by utilizing EPS in situ and collaborating with Fe (III) and H2O2 so as to regulate the performance of Fenton oxidation for efficiently enhancing the dewaterability. Results displayed the specific resistance to filtration (SRF) reduced from 34.1 ± 2.4 × 1012 m/kg to 16.2 ± 1.5 × 1012 m/kg with only 0.15 mmol Fe(III)/g VSS and 1.46 mmol H2O2/g VSS. Notably, the formation of relative stable Fe(III)-EPS complex was found under the interval addition of Fe(III) and H2O2. Four types of reactive species (hydroxyl radical (•OH), singlet oxygen (1O2), superoxide radical (O2•-) and Fe(IV)) which could effective destroy EPS structure during conditioning process, were generated after the addition of H2O2. It effectively promoted the transition from intracellular oxidation to extracellular oxidation under Fenton oxidation conditions, which reduced negative effects of cell lysis under excessive oxidation during sludge conditioning. The structure of EPS damaged significantly during the oxidation process, leading to the effective conversion of bound water to free water. Meanwhile, the existence of dissociative Fe(III) promoted the aggregation of sludge flocs, generating large channels or pores for sludge water to discharge, and then improving the dewaterability. Overall, [Fe(III)-EPS]/H2O2 treatment as an efficient sludge conditioning method can provide guidance for sludge dewaterability enhancement in urban sludge treatment and disposal.

Insight into the evolution of microbial communities and resistance genes induced by sucralose in partial nitrification system with triclosan pre-exposure

Sucralose (SUC), an artificial sweetener widely used in food, beverages and pharmaceuticals, is frequently detected in various environmental matrices. Triclosan (TCS) is commonly used as a disinfectant and often co-exists with SUC in sewage environments. This study investigated the effects of SUC (0.1–10 mg/L) on the transmission of intracellular and extracellular antibiotic resistance genes (ARGs) in the partial nitrification systems with and without TCS pre-exposure. The reactors operated for 150 days, and SUC did not affect ammonia oxidation performance, while TCS led to the maintenance of partial nitrification. The types and abundances of extracellular ARGs in sludge and free ARGs in water increased significantly after TCS pre-exposure when faced SUC stress, which might be caused by a decrease in α-Helix/(β-Sheet + Random coil). SUC was more easily to enrich ARGs in partial nitrification systems with TCS pre-exposure, exacerbating the risk of ARGs transmission. The microbial community showed stronger relationships to cope with the direct stress of SUC, and the functional bacteria (Thauera and Nitrosomonas) in TCS pre-exposure system might be potential hosts of ARGs. This study might provide insights for better understanding the fates of SUC in partial nitrification systems and the ecological risks in wastewater containing TCS and SUC. Environmental ImplicationSucralose (SUC) is often detected in the environment and considered as an emerging contaminant due to its soaring consumption and environmental persistence. Triclosan (TCS) is an antibacterial agent that often co-exists with SUC in personal care products and sewage environments. During 150 d, two partial nitrification reactors with and without TCS pre-exposure were established to study the effects of SUC on nitrification performance, antibiotic resistance genes (ARGs) and microbial communities. This study showed the refractory nature of SUC, and SUC led to the transmission of extracellular ARGs in partial nitrification system with TCS pre-exposure, exacerbating the risk of ARGs dissemination.

The potential of electron beams for the removal of microplastics from wastewater and sewage sludge

Wastewater and sewage sludge treatment plants are known to be important entrance routes for microplastics (MPs) into the aquatic environment. Although traditional wastewater treatment plants with primary and secondary purification processes can remove over 99 % of MPs, the majority of these are believed to be deposited into the sewage sludge. This provides a route into the environment, especially if the treated sludge is used as a fertilizer on agricultural land. Although methods do exist for the removal of MPs from water, there are limited studies with sludge. The possibility of using electron beam treatment for the removal of microplastics from wastewater and sewage sludge has been investigated in the laboratory using both tap water and actual sewage sludge. Microplastics were created from six types of plastics in daily use, <1.5 mm in size, and treated with a range of doses in tap water and in sewage sludge, taken from a sewage sludge treatment plant, both before and after anaerobic digestion, with a 10MeV accelerated electron beam. In this treatment, the electrons were found to act as a coagulant by modifying the surface charge of the microplastics. This significantly increases the sedimentation of four out of six of the types of MP in both water and sludge, while the other two largely remain floating. Density separation techniques of the treated samples have then demonstrated removal efficiencies in the range 85–95 % for five of the MP types and of around 70 % for the sixth at reasonable EB doses. This potentially provides a route to high efficiency removal from sludge.

Effects of the supported FeOOH on catalyzing gasification of oily sludge in supercritical water

FeOOH/AC-, FeOOH/Al2O3- and FeOOH/ZnO-supported catalysts were synthesized by immersion, hydrothermal hydrolysis, and hydrothermal methods, and used for supercritical water gasification (SCWG) of oily sludge. Under the same conditions, compared to FeOOH/Al2O3 and FeOOH/ZnO, the catalytic effect of FeOOH/AC was superior. When the concentration is 5% and the loading is 10%, the hydrogen production rate with FeOOH/AC composite is the highest, which is 4.638 mmol/g, and the hydrogen gasification efficiency (HE) is 89.50%. The reaction mechanism of FeOOH composites in the SCWG was also investigated. These results indicate that FeOOH composites are potential catalysts for oily sludge treatment.

Sustainable use of wastes as reactive material in permeable reactive barrier for remediation of acid mine drainage: Batch and continuous studies

The aim of this work was to evaluate the feasibility of the use of different industrial and agricultural wastes as reactive materials in Permeable Reactive Barriers (PRB) for Acid Mine Drainage (AMD) remediation. Sugar foam (SF), paper mill sludge (PMS), drinking water sludge (DWS) and olive mill waste (OMW) were evaluated in terms of pH neutralization and metal removal from AMD. Laboratory batch tests and continuous pilot scale up-flow columns containing 82% of Volcanic Slag (VS), as porous fill material, and 18% w/w of one of the industrial and agricultural wastes previously indicated, were tested.From the batch tests it was observed that the reactive material presenting the best results were the SF and the PMS. The results obtained in all the PRB were accurately described by a pseudo-first order model, presenting coefficient of determination higher than 0.96 in all the cases.During the continuous operation of the PRB, the porosity and hydraulic retention time (HRT) of most of the up-flow columns strongly decreased due to chemical precipitation and biofilm growth. The SF presented a significant number of fine particles that were washed out by the liquid flow, generating an effluent with very high total suspended solid concentration. Despite SF was the material with the highest alkalinity potential, the reduction of the HRT limited its neutralization and metal removal capacity. PMS and DWS presented the best pollutant removal yields in the continuous operation of the PRB, ranging from 55 to 99% and 55–95% (except in the case of the Mn), respectively. These results allowed the metal removal from the AMD. Additionally, these wastes presented very good biological sulphate reduction.Based on these results, the use of PMS and DWS as reactive material in PRB would allow to simultaneously valorise the industrial waste, which is very interesting within the circular economy framework, and to remove metals from the AMD by means of a low-cost and environmentally sustainable procedure.

Sludge-derived biochar: Physicochemical characteristics for environmental remediation

The global production of fecal wastes is envisioned to reach a very high tonnage by 2030. Perilous handling and consequential exposition of human and animal fecal matter are inextricably linked with stunted growth, enteric diseases, inadequate cognitive skills, and zoonoses. Sludge treatment from sewage and water treatment processes accounts for a very high proportion of overall operational expenditure. Straightforward carbonization of sludges to generate biochar adsorbents or catalysts fosters a circular economy, curtailing sludge processing outlay. Biochars, carbonaceous substances synthesized via the thermochemical transformation of biomass, possess very high porosity, cation exchange capacity, specific surface area, and active functional sorption sites making them very effective as multifaceted adsorbents, promoting a negative carbon emission technology. By customizing the processing parameters and biomass feedstock, engineered biochars possess discrete physicochemical characteristics that engender greater efficaciousness for adsorbing various contaminants. This review provides explicit insight into the characteristics, environmental impact considerations, and SWOT analysis of different sludges (drinking water, fecal, and raw sewage sludge) and the contemporary biochar production, modification, characterization techniques, and physicochemical characteristics, factors influencing the properties of biochars derived from the aforestated sludges, along with the designing of chemical reactors involved in biochar production. This paper also manifests a state-of-the-art discussion of the utilization of sludge-derived biochars for the eviction of toxic metal ions, organic compounds, microplastics, toxic gases, vermicomposting approaches, and soil amelioration with an emphasis on biochar recyclability, reutilization, and toxicity. The practicability of scaling up biochar generation with multifaceted, application-accustomed functionalities should be explored to aggrandize socio-economic merits.

Enhancing biogas production in anaerobic digestion of MSW with addition of bio-solids and various moisture sources

This study aimed to investigate the influence of moisture content on the anaerobic digestion of municipal solid waste (MSW) with the addition of leachate, tap water, wastewater, and sewage sludge. To accomplish this, ten sets of batch experiments were conducted to examine the impact of these various moisture sources on the rate of degradation, indicated by cumulative biogas yield, volatile solids (VS) and total solids (TS) removal. The addition of sludge with leachate and wastewater to MSW resulted in biogas yields that were approximately 30 % higher than the biogas yield from MSW and wastewater alone. Based on the observations of VS removal, it was observed that the addition of sludge degraded about half of the substrate. Therefore, it was observed that the addition of 10 % sludge with leachate and wastewater to MSW provides the best outcomes. The lowest biogas yield was observed with the mixing of tap water with MSW. Further, it was determined that the optimal moisture content for MSW degradation should be greater than 75 % of field capacity (FC). The cumulative biogas yield decreased by more than 50 % when the moisture contents decreased from 100 % to 50 % of FC. The reduction in biogas production at low moisture contents is attributed to limited mass transfer, and the hydrolysis rate also slightly decreases with an increase in total solids. The kinetic study was also carried out using the first order, modified Gompertz, Transference, and Logistic models, and the predicted cumulative biogas yield was compared with the experimental data. The modified Gompertz and Logistic models showed the best fit (R2 ≥ 0.994) with the experimental data for all the sets. The sludge, leachate, and wastewater are produced in large quantities in developing countries, and this study may provide a possible utilization strategy of these wastes for accelerated degradation of MSW.

Tracing morphological characteristics of activated sludge flocs by using a digital microscope and their effects on sludge dewatering and settling

ABSTRACT In wastewater treatment by the activated sludge (AS) process, settleability and dewaterability of AS are key issues that are directly related to the treated water quality and sludge treatment costs. Several studies investigated the relationship between the shape of AS flocs and their settling/dewatering property. To quantify the floc morphology, it is imperative to attach a camera to a microscope or move the stage manually. Hence, labour and equipment costs may increase. In this study, by combining a digital microscope and an automatic stage, more than 100 magnified floc images were rapidly obtained from one AS sample dropped on a slide glass, and shape parameters were collectively calculated using an analysis software. During 1-year monitoring of four wastewater treatment plants in Sapporo City (Hokkaido, Japan), the morphological parameters and extracellular polymeric substances (EPS) quantity/quality of AS were analyzed on the basis of their correlation to the time to filtration (TTF) and sludge volume index (SVI), which are indicators for describing the dewatering and settling properties of AS, respectively. In one plant, larger, denser, and smoother flocs tended to contain less EPS and exhibited better sludge dewaterability. In another plant, larger, denser, and smoother flocs were considered to contribute to better settlement. Especially, an equivalent high-density floc diameter and the ratio of mixed liquor suspended solids (MLSS) concentration to the total floc area were commonly suggested to explain AS dewaterability and settleability.

Mechanical Characteristics of Developed Brick from Drinking Water Sludge Under Different Firing Temperatures and Rice Husk Ash Contents

There is a considerable interest in making alternative bricks using wastes. Firing temperature has been significantly improved the mechanical qualities of bricks. The aim of this study was to investigate into the impact of firing temperature and rice husk ash content on the mechanical properties of drinking water sludge bricks (DWS). Two types of bricks were produced; bricks made of 100% DWS (DWS100) and bricks with 80% DWS and 20% RHA (DWS80). These samples were subjected to different thermal variations of 300 °C and 700 °C for three hours. The unfired brick samples were also prepared for reference. The volume changes of the DWS100 bricks increased as the firing temperature climbed up to 500 °C, before dropped at 700 °C. A similar behaviour was also exhibited by DWS80 bricks, however it shrunk at earlier temperature of 500 °C. At 500 °C and 700 °C, the density of bricks decreased dramatically, with DWS80 bricks consistently being lesser than DWS100 bricks. The water absorption of DWS80 brick began to decrease at 500 °C, a lower temperature than that of DWS100, as the firing temperature climbed. RHA-added bricks (DWS80) were anticipated to absorb more water than DWS100 bricks, but this did not occur. This presumably induced by the constriction of clay mineral structure rather than organic matter removal at high temperature per se. The compressive strength increased with the increase in temperature. It can be inferred that RHA can decrease the compressive strength of RHA-added bricks, despite the fact that a higher fire temperature significantly increased their strength.