Search Results (21)

Microbially induced concrete deterioration (MID) poses a significant and urgent challenge to urban sewerage systems globally, particularly in tropical coastal regions. Despite the acknowledged importance of biofilms in MICC, limited research on sewer pipe biofilms has hindered a comprehensive understanding of their deterioration mechanisms. To overcome this limitation, our research employed multiple staining techniques and digital volume correlation (DVC) technology, creating a new method to analyze the microstructure of biofilms, precisely identify the components of EPSs, and quantitatively examine MID mechanisms from a microscopic viewpoint. Our results revealed that the biofilm on concrete surfaces regulates the types of amino acids, thereby creating an environment conducive to microbial aggregate survival. Additionally, salinity significantly influences biofilm component distribution, while proteins play a pivotal role in biofilm mechanical stability. Notably, a high salinity fosters microbial migration within the biofilm, exacerbating deterioration. Through this multidimensional inquiry, our study established an advanced echelon of comprehension concerning the intricate mechanisms underpinning MICC. Meanwhile, by peering into the biofilms and elucidating their interplay with concrete, our findings offer profound insights, which can aid in devising strategies to counter urban sewer system deterioration. Full article

Long-distance sewerage network systems have serious vulnerabilities, specifically pipeline blockage, leakage, sedimentation, mixed connection, and other problems. A vulnerability evaluation system for a sewage network was established in this study with the comprehensive consideration of three aspects: basic attributes of the sewage network, operation and maintenance (O&M) drivers, and structural level. First, we obtained vulnerability indicators for the sewage pipeline network system through data collection and the preliminary selection and screening of indicators. The extent of the importance of each criterion level to the vulnerability was clarified through principal component analysis (PCA), with the basic attribute indicators being the per capita GDP (X3) and the urbanization rate (X5), the O&M-driven indicators being the daily per capita wastewater treatment volume (X7) and the industrial wastewater discharge volume (X8), and the structural-level indicators being the pipe diameter (X13) and the flow capacity (X15). Qingshanhu District, Jiangxi province, was taken as an example for diagnosing and evaluating vulnerability. Using the ranking size of PCA indicators as the evaluation level of the importance for the analytic hierarchy process (AHP) indicators, a hierarchical structure model was established. The evaluation value was obtained by weighting the hierarchical structure model results with the scores of each indicator. The comprehensive evaluation values of basic attributes, operation and maintenance drivers, and structural level were 58.38, 68.67, and 73.17, which corresponded to vulnerability levels of III, II, and II, respectively. Full article

This study undertakes a comprehensive experimental and numerical analysis of the structural integrity of buried RC sewerage pipes, focusing on the performance of two distinct jointing materials: cement mortar and non-shrinkage grout. Through joint shear tests on full-scale sewer pipes under single point loading conditions, notable effects on the crown and invert of the joint were observed, highlighting the critical vulnerability of these structures to internal and external pressures. Two materials—cement–sand mortar and non-shrinkage grout—were used in RC pipe joints to experimentally evaluate the joint strength of the sewerage pipes. Among the materials tested, cement–sand mortar emerged as the superior choice, demonstrating the ability to sustain higher loads up to 25.60 kN, proving its cost-effectiveness and versatility for use in various locations within RC pipe joints. Conversely, non-shrinkage grout exhibited the lowest ultimate failure load, i.e., 21.50 kN, emphasizing the importance of material selection in enhancing the resilience and durability of urban infrastructure. A 3D finite element (FE) analysis was also employed to assess the effect of various factors on stress distribution and joint deformation. The findings revealed a 10% divergence between the experimental and numerical data regarding the ultimate load capacity of pipe joints, with experimental tests indicating a 25.60 kN ultimate load and numerical simulations showing a 23.27 kN ultimate load. Despite this discrepancy, the close concordance between the two sets of data underscores the utility of numerical simulations in predicting the behavior of pipe joints accurately. This study provides valuable insights into the selection and application of jointing materials in sewerage systems, aiming to improve the structural integrity and longevity of such critical infrastructure. Full article

In Japan, there are a massive number of sewage pipes buried in the ground. In order to operate sustainable sewerage systems, it is necessary to estimate the soundness of sewage pipes accurately and to conduct repairs and other measures according to the soundness of the pipes. In previous studies, statistical and machine learning methods have been used to estimate the soundness of sewage pipes, but all of these studies formulated the soundness of sewage pipes as a binary classification problem (e.g., good or poor). In contrast, this study attempted to predict the soundness of sewage pipes in more detail by setting up four classes of pipe soundness. Inspection data of sewage pipes in City A were used as training data, and XGBoost was used as the machine learning model. Machine learning models have a high prediction performance, but the uncertainty of the prediction basis is an issue. In this study, SHAP (Shapley additive explanations), an Explainable AI method, was used to interpret the model to clarify the influence of sewer pipe specifications (e.g., pipe age) and topographical specifications (e.g., annual precipitation) on the prediction, and to extract deterioration factors. By interpreting the model using SHAP, it was possible to quantify whether factors such as pipe age and pipe length have a positive or negative impact on the deterioration of sewage pipes. Previous studies using machine learning methods have not clarified whether factors have a positive or negative effect on deterioration. The knowledge on deterioration factors obtained in this study may provide useful information for the sustainable operation of sewage systems. Full article

Sewerage systems-related solid waste accumulates in considerable quantities in urban water systems, including rainwater drainage pipes, pumping stations, grease traps, grit chambers, and septic tanks. Traditional management methods, such as sanitary landfilling, incineration, and composting, not only endanger the environment but also consume a significant amount of land. To address this problem, a variety of waste was collected from a terminal and different facilities in sewerage systems, and the characteristics of solid waste were tested and analyzed. The corresponding appropriate approaches to resource recovery strategies were proposed in detail. The solid waste in the wastewater treatment plant (WWTP) contains low organic matter content and a certain quantity of heavy metals, making recycling difficult. Before the solid waste enters the WWTP, the strategy of pre-sorting, treating, and recycling the solid waste is worth recommending. The waste was divided into three categories based on its nature, and corresponding resource utilization strategies were proposed. A small part of solid waste that is not suitable for pre-recycling can be discharged normally and enter the WWTP for treatment. This paper provides a scientific basis for the green resource utilization of solid waste in the field of sewerage systems in developing countries. Full article

This research is an assessment of existing liquid waste disposal systems in West Africa and their performances over the years, using systems in Ghana and Nigeria as a case study. The main purpose of the study was to improve upon the sustainability of the systems, which according to earlier research activities, have been failing and resulting in health hazards. Ghana and Nigeria were selected because, from occurrences, especially in the West African sub-region, the two countries dictate the pace in contributions to the body of knowledge. Many portable liquid waste disposal systems were identified as part of the research process, as earlier researchers called for a paradigm shift from the practice of Europeanized systems that had not been successful in the entire sub-region. Many reasons have been attributed to the failures, and more worryingly, the systems continue to be operational despite their states of malfunctioning. Frequent power cuts and ineffective revenue generation contribute to numerous problems. West Africans have been enduring these occurrences for a long time with no solution in place. In a few instances, raw sewage is piped into a central biogas system for the future generation of electrical power; this system was found to be right on point because it was determined from the initial stages of development that by-products could be used to mitigate the high costs of maintenance. Another system that combines a biofil digester with its treated wastewater being channeled into a saturation pond was found to be a success because the outflow from the biofil was not meant to be channeled into main drains, as it did not wholly meet EPA approvals. The centralized sewage treatment systems have been functioning well in advanced countries; however, they are found to be ineffective in developing countries. The reasons included lack of availability for spare parts and coagulants, etc., which were normally imported. Additionally, when a larger community is targeted, revenue generation becomes a problem, thereby affecting return on investments (ROI) and operating and maintenance (O&M). None of the available central sewerage systems harvest by-products, making revenue generation a difficult task. The portable systems have been discussed in this research study, with examples and a record of performance over the years that could contribute to the body of knowledge in the field of sustainability for sewage treatment processes suitable for West Africa and for the whole of sub-Saharan Africa. Full article

Wastewater collection, transport, and treatment systems are essential to ensure human and environmental well-being. The Escuela Superior Politécnica del Litoral (ESPOL), has been implementing various sanitary sewerage systems; however, population growth has given rise to discussion on the installed capacity versus the necessary capacity for the future population in the sustainable management of water resources. Therefore, this study aimed to develop a sanitary sewerage master plan by analysing the existing situation and applying technical criteria for the sustainable use of wastewater on a university campus. The methodology consisted of (i) evaluation and diagnosis of the area studied through data collection and processing, (ii) design of the sanitary sewerage system considering area-expansion zones, and (iii) SWOT analysis of a proposal to enhance wastewater transport and treatment systems. The proposal contemplates designing a sanitary sewer system that will manage the collection, transport, and treatment of wastewater over 15 years for 5667 inhabitants located in three expansion zones with occupation periods of 5, 10, and 15 years. The sewerage system comprises a pipe network 1.19 km long and 200 mm in diameter, transporting 12.37 L/s of wastewater generated to two treatment systems that guarantee efficient depuration and subsequent reuse. This design was complemented by a SWOT analysis of the existing sanitation system developed by experts in the area, which included optimising existing treatment systems and reusing wastewater for irrigation of green areas as tertiary treatment within the circular economy. The methodology used in the study allows us to offer a tool for efficiently managing wastewater on a university campus, guaranteeing human well-being, and promoting the circular economy of water. Full article

Urban wastewater effluents bring large amounts of nutrients, organic matter, and organic microcontaminants into freshwater ecosystems. Ensuring the quality of wastewater treatment (WWT) is one of the main challenges facing the management of wastewater treatment plants (WWTPs). However, achievement of high-quality standards leads towards significant energy consumption: usually the more intensive WWT process requires additional energies. Energy efficiency at WWTP is actual mainstream on the current sustainable development agenda. The WWTP processes and methods can be considered from the standpoint of material and energy flows according to circular economy paradigm, which offers great possibilities to reuse waste originating from WWT in order to receive renewable energy. The correlation between energy and quality issues to evaluate WWTP efficiency is of a great scientific and practical interest. The main goal of the paper is to check the dependency between these two main issues in WWTP management—WWT quality and energy efficiency—and to determine possible limits of such relation. The municipal sewerage system of Ekaterinburg, Russia was studied within this paper. The total length of centralized sewerage system in Ekaterinburg is over 1500 km of pipes within two main sewerage basins: northern and southern. The methodological framework for the current research consisted of three steps: (i) WWT quality evaluation, (ii) energy efficiency evaluation, and (iii) WWTP Quality/Energy (Q/E) efficiency dependency matrix. For the purpose of research, authors investigated the 2015–2018 period. The results showed that the outputs correlate with the technical conditions of WWTPs and the implementation of the best available techniques (BATs): most of the northern WWTP values are referred to the green zone (good rank), while the southern WWTP values are situated generally in the orange zone (unsatisfactory rank). The proposed methodological approach for Q/E dependency of WWT process creates a strong but simple tool for managers to evaluate the current success of the operation of WWTP and progress towards circular economy practices implementation. Full article

Microbiologically induced corrosion (MIC) leads to the degradation/deterioration of concrete pipes, due to the formation of gypsum. Magnesium hydroxide powders may protect the concrete surface by maintaining alkaline pH values at the surface, or by neutralizing the biogenic produced sulfuric acid. An accelerated sulfuric acid spraying test in a custom-made spraying chamber used to examine the consumption of magnesium hydroxide coating, which was applied on poly (methyl methacrylate) plates, instead of applying it on concrete substrates. In that way, only the magnesium hydroxide coating can interact with the acid and can be examined separately. Surface pH measurements and the mass changes were daily conducted, during the four-day accelerated spraying test. The mineralogical phases of the surface were determined by using X-ray Diffraction (XRD) measurements. Full article

The Microbiologically Induced Corrosion (MIC) of concrete sewer pipes is a commonly known problem that can lead to the destruction of the system, creating multiple public health issues and the need for costly repair investments. The present study focuses on the development of a magnesium hydroxide coating, with optimized properties to protect concrete against MIC. The anti-corrosion properties of the respective coating were evaluated by using short and long duration accelerated sulfuric acid spraying tests. The coating presented satisfying adhesion ability, based on pull-off and Scanning Electron Microscopy (SEM) analysis measurements. The surface pH of the coated concrete was maintained at the alkaline region (i.e., >8.0) throughout the duration of all acid spraying tests. The consumption of the coating, due to the reaction (neutralization) with sulfuric acid, was confirmed by the respective mass and thickness measurements. The protection ability of this coating was also evaluated by recording the formation of gypsum (i.e., the main corrosion product of concrete) during the performed tests, by X-ray Diffraction (XRD) analysis and by the Attenuated Total Reflectance (ATR) measurements. Finally, a long duration acid spraying test was additionally used to evaluate the behavior of the coating, simulating better the conditions existing in a real sewer pipe, and the obtained results showed that this coating is capable of offering prolonged protection to the concrete substrate. Full article

The weather derivatives market as an instrument of effective weather risk management is still not flexible enough for many industries. The water supply and sewerage industry is sensitive primarily to heavy rainfalls and periods of high and low temperatures: days with heavy rainfall may cause a hydraulic overload of the sewerage systems; on hot days, the water demand increases significantly; on frost days, the risk of water pipe failure grows. The work aimed to summarise methods of weather risk management and propose indices that will help to protect the interests of the water supply and sewerage industry in Poland. Three indices were proposed: a daily precipitation index, frost day index, and hot day index. The frequency of reaching these indices in Poland was verified with the use of meteorological data from 1970–2019, for 19 locations. The non-parametric Mann-Kendall test was used to determine the climate change impact on the exceedance frequency of the proposed indicators. The results showed that the indexes were exceeded in the past once every 6 years, on average. The hot day index was exceeded the least often, but it was the only one with a clear (growing) trend observed. Full article

The bending performance of a basalt-polypropylene fiber-reinforced concrete (HBPFRC) was characterized by testing 24,400 × 100 × 100 mm³ prismatic specimens in a four-point bending test JSCE-SF4 configuration. The type and content of both fibers were varied in order to guarantee different target levels of post-cracking flexural performance. The results evidenced that mono-micro basalt fiber reinforced concrete (BFRC) allows the increase of the flexural strength (pre-cracking stage), while macro polypropylene fiber reinforced concrete (PPFRC) can effectively improve both bearing capacity and ductility of the composite for a wide crack width range. Compared with the plain concrete specimens, flexural toughness and equivalent flexural strength of macro PPFRC and the hybrid fiber-reinforced concrete (HFRC) increased by 3.7–7.1 times and 10–42.5%, respectively. From both technical and economic points of view, the optimal mass ratio of basalt fiber (BF) to polypropylene fiber (PPF) resulted in being 1:2, with a total content of 6 kg/m³. This HFRC is seen as a suitable material to be used in sewerage pipes where cracking control (crack formation and crack width control) is of paramount importance to guarantee the durability and functionality of the pipeline as well as the ductility of the system in case of local failures. Full article

Several coatings and linings have been examined and used for the protection of sewer concrete pipes, against mainly biogenic-provoked corrosion due to the production of bio-sulfuric acid, leading to the degradation of the pipes’ structure and eventually, to their collapse and need for costly replacement. This study aimed to examine the potential differences between five different magnesium hydroxide coatings, prepared from powders presenting different purity, surface area and pore size distribution, when applied as corrosion protection agents. These coatings were tested by using accelerated sulfuric acid spraying tests, both in dry and wet coating conditions. The coating adhesion ability and their microstructure were examined by the application of pull-off measurements and of SEM analysis, respectively and were found to present certain differences, regarding the adhesion ability and the surface morphologies. During the acid spraying procedure, the surface pH and the mass change of coated concrete specimens were recorded daily. The surface pH was reduced towards acidic values and the mass reduction approached almost −20% in comparison with the initial coating mass for certain cases. Additionally, the hardness and roughness of concrete surface under the coating layer (i.e., the interface between the coating and the surface) after four days of acid spraying, exhibited much smaller changes (due to protection) in contrast to the uncoated concrete specimens (used as blank/comparison experiments), which were found to be highly affected/corroded. The formation of concrete corrosion and coating by-products, as noticed after the respective chemical reactions, was recorded by X-ray diffraction (XRD) measurements and the respective quantification of obtained results. In all the coated specimens only very small amounts of the major by-product (gypsum) was observed, indicating that the concrete surface was sufficiently protected from sulfuric acid attack. Full article

The design of sustainable sewerage infrastructure is fundamental for achieving long-term sustainability goals. Piping systems are essential components in the water supply chain and in waste disposal systems worldwide. Among possible designs for concrete pipes, steel cages consisting of curved rebars have been predominantly used as reinforcement. However, structural fibres have emerged as an attractive technical and economical alternative for substituting steel cages. Due to increasing urbanisation, thousands of kilometres of pipes will be constructed in the near future. At present, decisions regarding reinforcement of concrete pipes are primarily cost-driven. To consider other aspects, it is fundamental to identify and quantify potential sustainability issues properly. Hence, this paper focuses on the sustainability analysis of reinforced concrete pipes using a multi-criteria decision-making method. A model based on criteria, indicators, weights and value functions is developed and calibrated by assessing various concrete reinforcement strategies (steel bars or steel/synthetic fibres). The main contributions of the article are the proposal and application of a model for the case of concrete pipes which can be adapted for other case studies; determining how different typologies of pipes contribute to the overall sustainability of infrastructure systems; and the use and application of a robust and interesting multi-criteria decision-making methodology. The results show that fibre reinforced concrete pipes are promising alternatives in social, economic and environmental terms. Both the model and results are expected to be useful to stakeholders in decision-making processes. Full article

Distribution of toilet facilities and low-cost small-bore simplified sewerage systems (SS) in peri-urban areas provide opportunities to improve public health, provide safely managed sanitation, and protect the environment in low-to-middle income countries. Smoothed particle hydrodynamics (SPH) offers opportunities for optimisation of ultra-low water usage systems, but not without computational challenges. Results from SPH modelling of low cost, low water usage sanitary appliances were compared to a validated 1D finite difference model (DRAINET) for evaluation and calibration. An evaluation of system performance linked solid transport capabilities to physical geometries. The SPH model was developed for a pour-flush toilet pan connected to a 100 mm diameter pipe. The scheme utilized a free surface turbulent model to evaluate solid (faecal) transport efficacy. Performance was greatly influenced by the artificial viscosity factor, ViscoBoundFactor, within SPH, relating to the interaction of fluid and fluid particles and fluid and boundary particles. Results indicate that an increase in this factor leads to a reduction in fluid velocity with an attendant reduction in solid transportation distance, leading to inaccuracies. Other issues such as the use of density and mass in the definition of solid characteristics made it less predictable than the established 1D model for predicting solid transport. Overall, SPH was found to be useful for characterising the geometry of the pour flush pan but not for whole system assessment. A hybrid method is thus recommended whereby the design and performance characteristics for the input stage can be modelling in SPH but the whole system pipe network evaluation is better suited to the 1D DRAINET model. Full article