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Abstract

The functions performed by sanitary sewers can be disrupted by blockages in the pipeline, especially in cities with aging systems and deteriorating pipes. The problem is acute in Australia, where the principal blockage cause is tree root intrusion. This paper presents an overview of the causes of sewer blockages, the scope of the asset management challenge, and the management practices employed by Australian water utilities. These views were developed through reviews of the literature and current management practices elicited in a collaborative research project involving a range of water sector partners and using qualitative techniques such as surveys, interviews, and workshops. This paper highlights that blockages occur because of a range of factors, of which root blockages are the most common in Australia. Issues that confound management of blockages are also described, along with a summary of management strategies. Optimizing the balance between proactive and reactive interventions was found to be a good management strategy to maximize service outcomes.
... The efficiency of the operation and maintenance efforts of municipalities on sewer networks can also be assessed based on the management of blockage related failures. Existing approaches to the management of blockages require a combination of proactive and reactive measures which have been described by authors such as Thomson (2008), DeSilva et al. (2011) andFontecha et al. (2016). However effective blockage management should be an optimized balance between proactive and reactive maintenance to maximize service outcomes at the lowest cost within operational budgeting constraints (DeSilva et al. 2011). ...
... Existing approaches to the management of blockages require a combination of proactive and reactive measures which have been described by authors such as Thomson (2008), DeSilva et al. (2011) andFontecha et al. (2016). However effective blockage management should be an optimized balance between proactive and reactive maintenance to maximize service outcomes at the lowest cost within operational budgeting constraints (DeSilva et al. 2011). Conventionally, reactive approaches are applied to assets with a perceived low consequence of failure, usually operated till failure occurs and associated with low recurrence blockages while proactive approaches are applied when the perceived consequence and cost implications of failure are considered to be high specifically high recurrence blockages According to Ugarelli et al. (2009) the expenditure on blockages are regular costs to municipalities. ...
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Sewer networks are expected to operate with minimal or no interruptions. The complex nature of randomly occurring failures in sewer networks arising from blockages significantly adds to the cost of operation and maintenance. Blockages are significant due to sewage backup or basements flooding, resulting from their occurrence. Continuous performance assessment of sewer pipe networks is necessary to ensure a required level of service at an acceptable cost. This study provides insight into the performance of the sewer pipe networks by assessing the proneness of the network to blockages. Furthermore it draws inferences at a holistic strategic level of influential explanatory factors of blockage proneness, using data available in the Swedish Water and Wastewater Association's benchmarking system. Results indicate that medium sized municipalities are prone to at least 30% more blockages per km per year compared to other municipalities. A hypothesis of explanatory factors includes reduced flow volumes, design and flow depth. Flow velocities below self-cleaning velocity in sewer pipe networks, encouraged by sluggishness of flow are responsible for increased possibility for sediment deposition and accumulation in sewers leading to blockages. This is also exacerbated by the deposition of non-disposables (wet wipes, baby diapers, hard paper etc.), accumulation of fats, oils and grease in sewers and increased water conservation measures.
... Os sistemas de drenagem artificiais existem para resolver o défice de infiltração e, consequentemente, para evitar as inundações (DeSilva et al., 2011;Cherqui et al., 2015). As complexas redes de drenagem subterrâneas existentes nas áreas urbanizadas têm como objectivo retirar a água da superfície, evitando a sua acumulação. ...
... B. Chen e Liu, 2014). Também as rupturas de condutas na via pública e a obstrução das sarjetas por ramos e folhas de árvores ou outros detritos podem provocar inundações e/ou contribuir para a sua existência (DeSilva et al., 2011;Rudari et al., 2014;Cherqui et al., 2015). ...
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Os diversos tipos de inundações podem distinguir-se pelos seus factores desencadeantes, processos hidrológicos, características hidrodinâmicas, extensão espacial e temporal e capacidade destruidora. Se as cheias progressivas e cheias rápidas são termos actualmente estabilizados cientificamente, o mesmo não sucede com as inundações urbanas. Actualmente assiste-se a uma multiplicidade de conceitos associados a este tipo de inundações, não permitindo uma correcta classificação das ocorrências. Neste artigo apresentam-se os conceitos e o enquadramento das cheias progressivas e rápidas, discutem-se as questões teóricas e metodológicas relativas às inundações urbanas e propõem-se os termos FREN (inundações relacionadas com a antiga rede de drenagem natural) e FUNN (inundações não relacionadas com a actual ou antiga rede de drenagem natural). Os danos materiais reportados às seguradoras no município de Lisboa no período 2000-2011 apontaram as FUNN como o tipo de inundação mais frequente (53% dos sinistros). Por outro lado, foram as FREN que geraram maiores consequências (58% das indemnizações). Os resultados obtidos demonstram a importância do relevo e das antigas linhas de água nos danos materiais resultantes de inundações.
... Futhermore, weak joints and cracks in old sewer pipes may lead to the intrusion of roots and other debris (Lu et al., 2000). Initially, intrusion of tree roots was identified as a great influence in spatial deposition (DeSilva et al., 2011;Ducoste et al., 2008) and Marlow et al., (2011) showed that blockages due to tree root intrusion can be of >75% for some utility areas in Australia. Since then, other solids such as disposable face masks, wet wipes, tampons, cotton buds, plastics, sanitary absorbents, grit and dirt have also been found in sewer networks. ...
Article
Treatment of wastewater with high levels of fat, oil, and grease (FOG), produced by the growing number (annually 2%) of food service establishments (FSEs), is a major concern for water utilities. About 30-40% of sewer blockages are caused primarily by the formation of FOG deposits in sewer pipes, and an annual additional maintenance cost is required for sewer management. To manage FOG deposition, FSEs are required to recover the FOG at the point of generation by installing grease interceptors (GIs) before release to the sewer system. The successful control of FOG deposition is largely dependent on clear understanding of its complex properties, pre-treatment processes, deposition mechanism and public awareness. The objective of this study is to provide a comprehensive understanding of the physicochemical properties of FOG, including particle size distribution and their removal efficiencies by existing GIs. Nowadays, generation of FOG particles of ≤45 µm is increasing because of the increasing use of automatic dishwashers. Current hybrid processes which comprise pre-treatment prior to GI use are ineffective since they are unable to completely remove particle sizes of ≤45 µm. Hence, there is potential for these particles to be released into the sewer system and eventually cause blockages. This critical review discusses the characteristics of effluents, including the particle size distributions generated from automatic dishwashers and handwash sinks. It concludes by providing some case studies and a perspective of the future opportunities to develop a novel GI process integrated with pre-treatment to remove particles of all sizes, including colloidal particles.
... From the centre towards the northern peripheries in municipality A, except the northwest, pipes with increased sagging potential showed a stronger degree of influence, 11 -15% more compared to pipes with higher root intrusion risk and higher CCTV grades. This explains to some degree why pipes in this area may be plagued with structural problems which may result in increased sediment deposition and higher vulnerability with close proximity to trees, ultimately leading to the occurrence of blockages DeSilva et al., 2011;Torres et al., 2017). Reduced depth of pipes correlating to increased blockage propensity is also observed in this area. ...
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Efficient management of sewer blockages requires increased preventive maintenance planning. Conventional approaches to the management of blockages in sewer pipe networks constitute largely unplanned maintenance stemming from a lack of adequate information and diagnosis of blockage causative mechanisms. This study mainly investigated a spatial statistical approach to determine the influence of explanatory factors on increased blockage propensity in sewers based on spatial heterogeneity. The approach consisted of the network K-function analysis, which provided an understanding of the significance of the spatial variation of blockages. A geographically-weighted Poisson regression then showed the degree of influence that explanatory factors had on increased blockage propensity in differentiated segments of the sewer pipe network. Lastly, blockage recurrence predictions were carried out with Random Forest ensembles. This approach was applied to three municipalities. Explanatory factors such as material type, number of service connections, self-cleaning velocity, sagging pipes, root intrusion risk, closed-circuit television inspection grade and distance to restaurants showed significant spatial heterogeneity and varying impacts on blockage propensity. The Random Forest ensemble predicted blockage recurrence with 60–80% accuracy for data from two municipalities and below 50% for the last. This approach provides knowledge that supports proactive maintenance planning in the management of blockages in sewer pipe networks.
... Sediment transport in sewers and sewage networks have been the topics of a few studies in recent years due to some concerns associated with the pollution to watercourses, blockage, and surcharging (DeSilva et al. 2011). In general, the sediment deposition occurs occasionally in sewers as a result of the intermittent nature of flow (Ghani 1993; Azamathulla et al. 2012). ...
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In this study, two nature-inspired optimization techniques such as firefly algorithm (FA) and butterfly optimization algorithm (BOA) are combined with adaptive neuro-fuzzy inference system (ANFIS) and group method of data handling (GMDH) models for optimal prediction of the complex phenomenon of volumetric concentration of sediment (Cv) in sewer systems. Three different scenarios based on the methods of dimensional analysis and forward selection are implemented for determining the input structure of ANFIS, GMDH, and regression models (multiple linear regression, MLR; stepwise regression; SR) regarding 13 independent hydraulic and geometric input variables. Several statistic criteria including the root-mean-square error (RMSE), mean absolute error (MAE), Nash–Sutcliffe efficiency (NSE), index of agreement (AI), coefficient of determination (R²), and comprehensive synthesis index (SI) as well as Taylor diagram were used to further quantify simulating and predicting accuracies. In comparison with the regression models and two empirical equations, the results obtained by standard machine learning models (ANFIS and GMDH) were very promising. However, such integration of FA and BOA noticeably improved the performance of ANFIS (around 7% improvement in RMSE criterion) and slightly optimized the performance of GMDH (less than 1% improvement in RMSE criterion) in modelling the process of Cv prediction. Graphic abstract
... FOG deposits are accumulated suspended solids in sewer systems and have an adhesive character. They can become firmly attached to interior sewer pipe walls, thereby substantially reducing and sometimes even completely blocking the wastewater flow (Desilva et al., 2011). They have a grainy, sandstone-like texture with high yield strengths (Keener et al., 2008) that require intensive cleaning activities such as hydraulic jetting (Dirksen et al., 2012;Mattsson et al., 2014). ...
Article
Fat, oil and grease (FOG) deposits are an important contributor to blockages in building drainage systems. Such blockages bring undesirable financial, health and environmental costs, and thereby burden society. It is unclear to what extent the behavior of inhabitants, and more precisely domestic FOG disposal, affects the occurrence of FOG blockages. For this study, samples of FOG blockages were collected from building drainage systems (kitchen drains and lateral house connections) and analyzed. The results showed that the deposits were calcium salts of fatty acids. Dissimilarities between the network locations demonstrate that, even at short distance, in-sewer transformation processes occur. Surveys were conducted to reveal information about FOG disposal patterns. Three households showed a clear link between the type of cooking oils used and the type of deposits collected.
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The present study deals with the problems of urban sewage system and trying to find out the geographical perspectives behind the same. For this assessment, previous literature has studied and analysed. Basically, the urban sewage system deals with the collection, treatment and disposal of the generated wastewater. Now a day, the continuous growth of population and the process of urbanization crating overload on the available service of the sewage system. The blockage, clogging, backwater, overflow etc are the major concern of the same. Resulted, many health issues, environmental pollution and hazards within the urban places. Dynamic nature of the city, lack of public awareness, challenging physical setup of the region and sewer construction, maintenance and cleaning issues, inappropriate collection and treatment, poor economy etc are the major geographical perspectives of the urban sewage system issues.
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