A qualitative analysis on implementing the sewer system for an indigenous village in the influence area of Belo Monte Hydroelectric Plant (Brazil)

In this article, the project and implementation of the sewer system in the Paquiçamba Village, as a condition for environmental licensing, was investigated. This village is surrounded by the influence of the Belo Monte Hydroelectric Plant (Brazil). This research aimed to characterize the context of ethnodevelopment, thus recognizing the social participation of the indigenous people. The research within a qualitative approach between 2009 and 2018 was based on primary data sources (through structured interviews) and secondary data (electronic files related to the environmental licensing). Data were analysed according to descriptive, focused and selective observations until reaching theoretical saturation. The organization of the data was followed by the organization of the themes, which formed a spiral of interconnected activities based on Creswell's proposal (2014). It was detected that indigenous involvement occurred at some moments in the elaboration of the sewage system project. The maintenance of ancestral habits in the disposal of excreta by a portion of the indigenous people, even with the sewage system in place, makes it essential to broaden the debate on the projects proposed on the environmental licensing processes. The Indigenous can not only have a consultative role, but assume a deliberative participation, being protagonists in conducting their own development.

Modeling the quality of sewage during the leaking of stormwater surface runoff to the sanitary sewer system using SWMM: a case study

This paper describes the application of the storm water management model (SWMM) for predicting the sewage quality in the sanitary sewer system of the study area resulting from the leaking of stormwater surface runoff to the system during rainfall events at different return periods. The concentrations of major pollutants were assessed in the sanitary sewer system at different rainfall intensities. Then, a solution to mitigate the problem was proposed using low impact development (LID) technology. The results of sensitivity analysis indicated that maximum build-up possible was the most sensitive parameter for model calibration. The model was calibrated using actual rainfall events, and statistical validation coefficients of R (0.81–0.82) and NMSE (0.0173–0.022) proved that the model is valid. The sewage quality assessment results showed that pollutants concentration increased to its maximum level at 20 min and gradually decreased to a slightly constant minimum value after 2 h. The proposed solution of LID reduced the pollutants concentrations by 82–88, 75–77, 52–55, and 7–10% for all pollutants at return periods of 2, 5, 10, and 25 years, respectively. To conclude, SWMM simulation successfully predicted the concentration of the pollutants, and leaking of stormwater surface runoff has changed the sewage quality.

Model predictive control based on artificial intelligence and EPA-SWMM model to reduce CSOs impacts in sewer systems

Urbanization and an increase in precipitation intensities due to climate change, in addition to limited urban drainage systems (UDS) capacity, are the main causes of combined sewer overflows (CSOs) that cause serious water pollution problems in many cities around the world. Model predictive control (MPC) systems offer a new approach to mitigate the impact of CSOs by generating optimal temporally and spatially varied dynamic control strategies of sewer system actuators. This paper presents a novel MPC based on neural networks for predicting flows, a stormwater management model (SWMM) for flow conveyance, and a genetic algorithm for optimizing the operation of sewer systems and defining the best control strategies. The proposed model was tested on the sewer system of the city of Casablanca in Morocco. The results have shown the efficiency of the developed MPC to reduce CSOs while considering short optimization time thanks to parallel computing.

Hydraulic and Structural Analysis of Complex Cross-Section Reinforced Concrete Pipes to Improve Sewage Flow in a Combined Sewer System

A complex cross-section reinforced concrete pipe that combines a sub-pipe for the flow of sewage in dry weather and a main pipe for the flow of rainwater was developed to reduce sedimentation of the combined sewer system in dry weather. The sub-pipe was designed, considering the flow velocity, constructability, and maintenance. By fitting the sewage data in the dry weather to the normal distribution, the ratio of the cross-sectional area of sewage flow to that of the pipe was determined to be approximately 0.418, which could cover 99.85% of the sewage volume of the target site. Based on this ratio, the diameter of the sub-pipe corresponding to the combined sewer system with a pipe diameter between 450 and 1300 mm was determined. The hydraulic performance analysis results showed that the flow velocity increased by 11 to 12% compared to the circular pipe based on the full sub-pipe and by more than 15% depending on the water level. The shear stress increased by more than 16.5%, and higher tractive force was observed. Structural safety was determined as the crack load and failure load far exceeded the minimum criteria, thereby verifying the feasibility and field applicability of the complex cross-section reinforced concrete pipe.

Method for assessing the impact of rainfall depth on the stormwater volume in a sanitary sewage network

Sanitary sewage network is relatively rarely considered as the cause of urban floods. Its hydraulic overload can result not only in flooding, but also sanitary contamination of subcatchments. Stormwater is the main reason for this overload. In contrast to the stormwater or combined sewer system, these waters infiltrate into the network in an uncontrolled way, through ventilation holes of covers or structural faults and lack of tightness of manholes. Part of stormwater infiltrates into the soil, where it leaks into pipelines. This greatly hinders assessing the quantity of stormwater influent into the sanitary sewer system. Standard methods of finding correlation between rainfall and the intensity of stormwater flow are ineffective. This is confirmed, i.a. by the studies performed in an existing network, presented in this paper. Only when residuals analysis was performed using the ARIMA and ARIMAX methods, the authors were able to develop a mathematical model enabling to assess the influence of rainfall depth on the stormwater effluent from the sewage network. Owing to the possibility of using the rainfall depth forecasts, the developed mathematical model enables to prepare the local water and sewerage companies for the occurrence of urban floods as well as hydraulic overload of wastewater treatment plants.

Comparative study between conventional and mechanical technology on fecal sludge treatment plants (FSTP) in Indonesia

In pursuit of access to wastewater services to reach the target of 100%, it is undeniable that the non-sewer system/on-site system should continue to be developed. The non-sewer system provides low-cost options, making access to wastewater infrastructure more affordable. As a further treatment of the fecal sludge produced from on-site technology such as septic tank, FSTP (Faecal Sludge Treatment Plant) is needed. This study was conducted on 4 FSTPs in Java Island, namely 2 conventional system FSTPs (Keputih FSTP, Surabaya and Betoyoguci FSTP, Gresik) and 2 mechanical system FSTPs (Duri Kosambi FSTP, Jakarta and Sumur Batu FSTP, Bekasi). The research was conducted by comparing performance indicators which are collection, treatment, human resources, and cost-efficiency, representing development priority aspects. Analysis of the development strategy was carried out by SWOT analysis. Based on performance indicator comparison, Duri Kosambi FSTP has the highest collection efficiency among the others. Treatment efficiency ranging around 60%, and human resources efficiency in all FSTPs ranging at 80%. Duri Kosambi FSTP has an acceptable cost efficiency level, while the rest are still dissatisfactory. Development strategy derived from SWOT analysis should include an effort to do scheduled desludging, partial investment from government, adjusting tariff, and optimizing FSTP capacity.