Search Results (52)

The contamination of ground and surface waters with micropollutants like estrogenic compounds and genotoxins is a major public health concern. Conventional wastewater treatment plants are currently not capable of completely removing those contaminants. In this study, we applied planar bioassays to investigate the genotoxicity and estrogenic activity of hospital and municipal wastewater from an Austrian treatment plant. Using the open-source 2LabsToGo platform in combination with the HPTLC-SOS-UmuC and HPTLC-YES assays, both genotoxic and estrogenic compound zones were detected in untreated wastewater. Genotoxic activity was found in sewage sludge filtrate and hospital wastewater, with bioanalytical concentrations ranging from 1.6 to 21.8 µg 4-NQO-EQ L⁻¹. Estrogenic responses were observed in the influent and hospital wastewater samples, with BEQ values between 3.5 and 16.0 µg E2-EQ L⁻¹. No activity was detected in the treated effluent, indicating efficient removal of these compounds during wastewater treatment. These results confirm the presence of biologically active micropollutants in hospitals and raw wastewater and demonstrate the suitability of planar bioassays for sensitive, spatially resolved detection. The use of portable equipment like the 2LabsToGo system suggests that on-site monitoring of estrogenic and genotoxic activities in wastewater is feasible and could support routine surveillance of treatment efficiency. Full article

Background: Kigali, Rwanda’s rapidly growing capital, faces major challenges in household-level Fecal Sludge Management (FSM), with over 89% of households using pit latrines and only 48% accessing unshared sanitation. FSM services are limited, costly, and poorly executed, leading to frequent illegal dumping. Objective: This review analyzes the literature on sanitation in Kigali to identify key gaps, synergies, and recommendations for improvement. Methods: Following PRISMA 2020 guidelines, 73 relevant publications were selected from various scientific and governmental sources. Publications were included only if they were published from 2013 to 2024 and had information on sanitation in Kigali. NOS and JBI tools were utilized to assess the quality of included publications. Results: Data were categorized into four themes, (1) access to sanitation, (2) FSM services, (3) public health, and (4) sanitation governance, and analyzed using thematic, narrative, and descriptive methods. Findings reveal a dysfunctional FSM service chain, weak policy enforcement due to overlapping responsibilities, underfunding, and limited private sector participation. These issues contribute to poor sanitation, inadequate hygiene, and prevalence of diarrheal diseases and Tropical Neglected Diseases, especially among young children. Conclusions: The review recommends strengthening governance and clarifying roles, enforcing adaptable regulations, promoting public–private partnerships, and managing the full FSM service chain more effectively. Future research should focus on developing context-specific technologies and financing strategies to support sustainable FSM solutions in Kigali. Full article

This article presents an innovative method for phosphate(V) removal from industrial wastewater using cerium(III) chloride as a coagulant, integrated with reagent recovery. The process combines coagulation, acid extraction, and multistage recovery of cerium and phosphorus, enabling partial reagent loop closure. Based on our previously published studies, at an optimised dose (81.9 mg Ce³⁺/L), phosphate(V) removal reached 99.86% and total phosphorus (sum of all phosphorus forms as elemental P), 99.56%, and 99.94% of the added cerium was retained in sludge. Reductions were also observed for TSS (96.67%), turbidity (98.18%), and COD (81.86%). The sludge (101.5 g Ce/kg, 22.2 g P/kg) was extracted with HCl, transferring 99.6% of cerium and 97.5% of phosphorus to the solution. Cerium was recovered as cerium(III) oxalate and thermally decomposed to cerium(IV) oxide. Redissolution in HCl and H₂O₂ yielded cerium(III) chloride (97.0% recovery and 98.6% purity). The HCl used for extraction can be regenerated on-site from chlorine and hydrogen obtained from gas streams, improving material efficiency. Life cycle assessment (LCA) showed environmental benefits related to eutrophication reduction but burdens from reagent use (notably HCl and oxalic acid). Although costlier than conventional precipitation, this method may suit large-scale applications requiring high phosphorus removal, low sludge, and alignment with circular economy goals. Full article

Untreated sewage sludge (SS) and misused stabilization technologies have contributed to great contamination and the accumulation of various pollutants in agricultural soils. Regarding micro-pollutants’ degradation, scalable and effective technologies are still scarce. Although many attempts at composting adaptations have been discussed, only a few have been tested individually under outdoor conditions. To investigate different composting methods (bioaugmentation and semipermeable cover) for the removal of micro-pollutants frequently found in SS, we performed a set of on-site experiments. Windrows of SS and olive pruning were used as the compostable material and were subjected to (i) bioaugmentation with the fungus Penicillium oxalicum, (ii) covered composting, (iii) covered and bioaugmented composting, and (iv) a conventional composting pile, which was included as a control. The entire experiment lasted 99 days. Bioaugmentation without cover increased the phosphorus content, favored a reduction in heavy metal content, and was the only treatment that reduced carbamazepine at the end of the process. Moreover, the inoculation of P. oxalicum under semipermeable cover increased the richness, diversity, and dominance of specific microbial taxa and total bacterial abundance. The four mature composts obtained met the standards required to be classified in the B fertilizer category, showing that we reduced most of the micro-pollutants, and passed the germination test. Full article

Wastewater treatment plants (WWTPs) generate significant emissions of gaseous substances, such as H₂S, NH₃, and VOCs, which cause discomfort and pose health risks to residents in surrounding areas. The objective of this study was to estimate pollutant concentrations under various scenarios through a mathematical modeling of the pollutant dispersion in the surrounding air using the AERMOD View software platform, version 11.2.0. In this study, four mathematical models with two different scenarios were conducted to illustrate the odor concentrations both on site and in nearby areas under the most unfavorable weather conditions. The “1st Highest Values” and “98th Percentile” metrics were used to represent the peak concentrations and to exclude the 2% of conditions with the worst-case dispersion, respectively. In the first scenario, under normal operating conditions with all treatment equipment functioning, the maximum on-site odor concentration was estimated at 36.8 ouE/m³ using the 1st highest value function, and it was 20.4 ouE/m³ using the 98th percentile function. The second scenario considered all emission sources, with the grease collection system of the de-sanding/grease separation Unit Line 1 and the sludge collection system of the primary settling decanter (Unit 4) out of service. In this case, the maximum on-site odor concentration reached 749 ouE/m³ over 98% of a one-year period and 956.5 ouE/m³ using the 1st highest value function. These findings underscore the necessity for ongoing monitoring, strict adherence to environmental regulations, and stakeholder engagement to improve mitigation techniques and foster community trust in environmental management. Regular inspections are essential to ensure that all equipment operates within normal parameters, supporting both regulatory compliance and improved operational efficiency, including the control of odor emissions. Full article

Wastewater treatment plants (WWTPs) consume a considerable amount of energy. They also generate energy in combined heat and power (CHP) units, which utilise biogas from the anaerobic digestion of sewage sludge to produce renewable electricity. Different prices apply to electricity generated on site in CHP units, to the purchase of electricity from the grid, to the sale of surplus electricity to the grid and energy tariffs, which motivates the optimisation of energy costs. This paper presents a strategy for optimising electricity costs by adapting on-site electricity generation in CHP units to the demand of the WWTP. The approach is designed for a CHP system that generates electricity in multiple internal combustion gas engines. It is implemented as a two-level control system, where the lower control level dynamically adjusts the power of the individual gas engines, and the upper control level optimises the desired total power, taking into account the current energy consumption of the WWTP, biogas reserves and electricity tariffs. The proposed concept was implemented at the Domžale-Kamnik WWTP. A six-month evaluation showed that electricity purchased from the grid could be reduced from 8.7% to 3.3% of the WWTP’s electricity consumption. This reduction affects the system economically, as electricity purchased from the grid at low and high tariffs is 35% and 76% more expensive than electricity generated on site (excluding the grid fee). This approach can be extended to balance dispatchable electricity generation at the WWTP to respond to short-term grid demand. Full article

The mechanical properties of faecal sludge (FS) influence its moisture retention characteristics to a greater extent than other properties. A comprehensive fundamental characterisation of the mechanical properties is scarcely discussed in the literature. This research focused on bulk and true densities, porosity, particle size distribution and zeta-potential, extracellular polymeric substances, rheology and dilatancy, microstructure analysis, and compactibility in the context of using the FS as a substitute for soil in land reclamation and bioremediation processes. FSs from different on-site sanitation systems were collected from around Durban, South Africa. The porosity of the FSs varied between 42% and 63%, with the zeta-potential being negative, below 10 mV. Over 95% of the particles were <1000 µm. With its presence in the inner part of the solid particles, tightly bound extra-cellular polymeric substances (TB-EPSs) influenced the stability of the sludge by tightly attaching to the cell walls, with the highest being in the septic tank with the greywater sample. More proteins than carbohydrates also confirmed characterised the anaerobic nature of the sludge. The results of the textural properties using a penetrometer showed that the initial slope of the positive part of the penetration curve was related to the stiffness of the sludge sample and similar to that of sewage sludge. The dynamic oscillatory measurements exhibited a firm gel-like behaviour with a linear viscoelastic behaviour of the sludges due to the change in EPSs because of anaerobicity. The high-TS samples exhibited the role of moisture as a lubricating agent on the motion of solid particles, leading to dilatancy with reduced moisture, where the yield stress was no longer associated with the viscous forces but with the frictional contacts of solid–solid particle interactions. The filtration–compression cell test showed good compactibility, but the presence of unbound moisture even at a high pressure of 300 kPa meant that not all unbound moisture was easily removable. The moisture retention behaviour of FS was influenced by its mechanical properties, and any interventional changes to these properties can result in the release of the bound moisture of FS. Full article

The management of drinking water treatment plant (DWTP) sludge is challenging for water treatment facilities. Previous studies reported mainly on handling sludge through landfilling, release into water bodies, discharge into wastewater treatment plants, onsite disposal, and incineration methods for the treatment of sludge. The limitations of these sludge-handling methods are well documented. This article focuses on the hierarchical approach as an alternative and comprehensive method for handling DWTP sludge. The core of hierarchical management streamlines the minimization of the generated DWTP sludge; treatment of DWTP sludge to reduce toxicity; changing of the physicochemical form of DWTP sludge; and finally, the reuse, recycling, and recovery of DWTP sludge. The premise is to achieve zero landfilling of DWTP sludge, establish a circular economy, generate job opportunities, and preserve the environment. Thus, this study also proposes two main technologies, which are gravity-based sludge separators for fractionating the sludge and photocatalytic membrane reactors (PMRs) as a technology for the treating and/or recovery of nutrients and minerals from DWTP sludge. Until the chemical deductive or minus approach becomes a reality in water treatment, the use of PMRs and gravity-based sludge separators will enhance the management of DWTP sludge when incorporated into the hierarchical approach. Full article

Microplastics have been widely detected in wastewater treatment plants, but there is still a significant dearth of research data on the removal efficiency of microplastics in such plants. The present study focused on three wastewater treatment plants situated in Zhengzhou, China. On-site sampling and Raman spectrum detection techniques were employed to identify microplastics in both wastewater and sludge samples, while the removal efficiency of microplastics was quantified for each plant. Results showed that the abundance of microplastics in influent exhibited ranging from 147.5 ± 2.6 to 288.8 ± 11.8 n/L, while the range in sludge samples was from 12,024.7 ± 1737.0 n/kg_dw to 20,818.4 ± 5662.0 n/kg_dw. The removal efficiencies of microplastics in the three WWTPs ranged from 76.2% to 91.2%. The primary components of microplastics were generally identified as fibers ranging in size from 10 to 100 μm. The samples collectively exhibited a total of seven distinct colors, with the predominant proportion being transparent. Polypropylene was the polymer type with the highest proportion. The sludge in WWTPs plays a pivotal role in the accumulation of MPs from wastewater bodies, necessitating increased attention toward its proper disposal in future endeavors. Full article

This study assesses the mechanical properties of mortars incorporating waste paper sludge-derived cellulose fibers. Compression and flexural tests were carried out on specimens prepared with cellulose fibers at different proportions, ranging from 0% to 2% of the total weight of the solid mortar constituents (cement, sand, and lime). In addition, a comparative analysis was carried out to evaluate the influence of the preparation method on the mechanical properties of the mortars. To this end, two series of mortars were studied: one prepared following a rigorous control of the preparation parameters and the other made without systematic parameter control to simulate typical on-site conditions. Finally, the applicability of both traditional and eco-friendly mortars in the construction of small-scale masonry walls was assessed through compression tests. Overall, the mechanical properties of mortars with cellulose fibers were comparable to those with 0% waste material, regardless of the production process. Regarding the compressive behavior of masonry walls, experimental tests showed significant similarities between specimens made with traditional and eco-friendly mortar. In conclusion, incorporating cellulose fibers into cement-based mortar shows considerable potential for building applications, enhancing the environmental benefits without compromising the mechanical behavior. Full article

The use of faecal sludge (FS) in anaerobic digestion (AD) requires a perfect knowledge of their composition. Considered as a very heterogeneous material, the high variability of FS can disturb biodigesters’ functionality and impact biogas production. Unique in West Africa, Kossodo’s biogas plant in Ouagadougou receives sludge from septic tanks and pit latrines. To evaluate the quality of sludge discharged in this treatment plant and its ability for AD, a characterization of 130 FS trucks from several onsite sanitation facilities was carried out. Physico-chemicals, including heavy metals and microbiological parameters, were analyzed using standard protocols. A biochemical methane potential test was employed to evaluate biogas yield. Results showed that raw sludge averaged 1.12% total solids (TS), 54.74% volatile solids (VS), 9253 mg/L chemical oxygen demand (COD), and 1645 mg/L biochemical oxygen demand (BOD). Settled faecal sludge exhibited higher levels of total coliforms, E. coli, helminth eggs, and heavy metals. Heavy metal levels met AD standards defined by VDI 4630, with decreasing toxicity order: Zn > Mn > Cu > Cr > Ni > Pb > As ≥ Hg. The carbon-to-nitrogen (C/N) ratio was 6.7 ± 4.3, indicating unsuitability for AD. Sludge settling increased C/N ratio by 46%, which was still below optimal AD conditions (20–30). Methane yield of raw and settled FS averaged 61 ± 0.2 and 156 ± 3.2 NL CH₄/kg VS removed, respectively. Co-substrate addition could enhance the methanogenic yield of these sludges. This study provides a valuable database on the characteristics of FS, supporting sustainable recovery options. Full article

The growing population and increasing urbanization have led to a surge in domestic wastewater generation, posing significant challenges for effective and sustainable treatment. The present study demonstrates a novel and sustainable approach for the onsite treatment of domestic wastewater using an integrated settler-based biofilm reactor (ISBR) with efficient biogas generation. The ISBR provides an optimized environment for the growth of biofilm, facilitating the removal of organic pollutants and pathogens. Moreover, the ISBR enables the recovery of a valuable resource in the form of biogas, thus enhancing the overall utility of the treatment process. The performance of the ISBR was comprehensively evaluated at laboratory scale through treating the actual domestic wastewater generated from the hostel of Manipal University Jaipur. The ISBR system was operated under an ambient environment at a hydraulic retention time (HRT) of 24 h. The results demonstrated remarkable efficiency in terms of chemical oxygen demand (COD), total suspended solids (TSS), and coliforms removal, with average removal efficiency being more than 90%. According to the COD mass balance analysis, 48.2% of the influent COD was recovered as bioenergy. The chromatogram revealed a high percentage of methane gas in the collected biogas sample. The field emission scanning electron microscope (FESEM) analysis of the accumulated sludge in the ISBR system depicted the morphology of methanogenic bacteria. Both the experimental and theoretical results confirmed the feasibility and sustainability of the ISBR system at the onsite level. Full article

With the increasing trend in the global average temperature, the UK’s water industry has committed to achieve Net Zero by 2030 and part of this includes cutting CH₄ emissions from sludge treatment facilities. Currently, emissions are estimated following the carbon accounting workbook guidelines and using default emission factors. However, this method might not be a true representation of emissions as these vary depending on many factors. The use of unmanned aerial vehicles (UAVs) has proved cost effective for environmental monitoring tasks requiring high spatial resolution information. Within the context of CH₄ emissions and in the last decade, the technology has been curtailed by sensor weight and size. Recent advances in sensor technology have enabled the development of a fit-for purpose UAV CH₄ sensor (U10) which uses Tuneable Diode Laser Absorption Spectroscopy. This study intends to develop a framework for CH₄ data collection strategies from sludge treatment centres using UAV-U10 technology and asset level CH₄ enhancement estimations based on geostatistical interpolation techniques and the mass balance approach. The framework presented here enables the characterization of spatial and temporal variations in CH₄ concentrations. It promotes asset level CH₄ enhancement estimation based on on-site measurements. Full article

The impact of adding a modified Ludzack–Ettinger (MLE) configuration with Nitrate Recycle (NRCY) on continuous-flow aerobic granulation has yet to be explored. The potential negative effects of MLE on sludge densification include that: (1) bioflocs brought by NRCY could compete with granules in feast zones; and (2) carbon addition to anoxic zones could increase the system organic loading rates and lead to higher feast-to-famine ratios. Two pilot-scale plug flow reactor (PFR) systems fed with real domestic wastewater were set up onsite to test these hypotheses. The results showed that MLE configuration with NRCY could hinder the sludge granulation, but the hindrance could be alleviated by the NRCY location change which to some extent also compensates for the negative effect of higher feast-to-famine ratios due to carbon addition in MLE. This NRCY location change can be advantageous to drive sludge densification without a radical washout of the sludge inventory, and had no effects on the chemical oxygen demand (COD) and nitrogen removal efficiencies. The PFR pilot design for the MLE process with a modified NRCY location tested in this study could be developed as an alternative to hydrocyclones for full-scale, greenfield, continuous sludge densification applications. Full article

In drilling and completion projects, sludge is formed as a byproduct when barite and oil are mixed, and later sticks to the casing. This phenomenon has caused a delay in drilling progress, and increased exploration and development costs. Since nano-emulsions have low interfacial surface tension, wetting, and reversal capabilities, this study used nano-emulsions with a particle size of about 14 nm to prepare a cleaning fluid system. This system enhances stability through the network structure in the fiber-reinforced system, and prepares a set of nano-cleaning fluids with adjustable density for ultra-deep wells. The effective viscosity of the nano-cleaning fluid reaches 11 mPa·s, and the system is stable for up to 8 h. In addition, this research independently developed an indoor evaluation instrument. Based on on-site parameters, the performance of the nano-cleaning fluid was evaluated from multiple angles by heating to 150 °C and pressurizing to 3.0 Mpa to simulate downhole temperature and pressure. The evaluation results show that the viscosity and shear value of the nano-cleaning fluid system is greatly affected by the fiber content, and the cleaning efficiency is greatly affected by the concentration of the nano-emulsion. Curve fitting shows that the average processing efficiency could reach 60–85% within 25 min and the cleaning efficiency has a linear relationship with time. The cleaning efficiency has a linear relationship with time, where R² = 0.98335. The nano-cleaning fluid enables the deconstruction and carrying of the sludge attached to the well wall, which accomplishes the purpose of downhole cleaning. Full article