A REVIEW OF DESIGN AND SIMULATION OF DECENTRALIZED WASTEWATER TREATMENT SYSTEMS FOR PERI-URBAN AREAS

International Research Journal of Engineering and Technology (IRJET)

e-ISSN: 2395-0056

Volume: 13 Issue: 02 | Feb 2026

p-ISSN: 2395-0072

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A REVIEW OF DESIGN AND SIMULATION OF DECENTRALIZED WASTEWATER TREATMENT SYSTEMS FOR PERI-URBAN AREAS USING HYBRID MODULAR UNITS Abdul Baqui Raheem1, Mr. Ushendra Kumar2 1Master of Technology, Civil Engineering, Lucknow Institute of Technology, Lucknow, India 2Head of Department, Department of Civil Engineering, Lucknow Institute of Technology, Lucknow, India

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Abstract - Rapid and unplanned expansion of peri-urban

areas has intensified pressures on conventional centralized wastewater infrastructure, necessitating context-sensitive and scalable treatment alternatives. Decentralized wastewater treatment systems (DEWATS), particularly those configured as hybrid modular units, have emerged as promising solutions due to their adaptability, lower capital investment, and potential for phased implementation. This review critically synthesizes existing literature on the design principles, process integration strategies, and simulation approaches applied to hybrid modular decentralized systems in peri-urban contexts. The paper examines commonly adopted treatment combinations—such as anaerobic reactors, constructed wetlands, membrane units, and advanced polishing processes—and evaluates their performance in terms of pollutant removal efficiency, operational reliability, and resource recovery potential. Furthermore, it analyzes the role of process-based modeling, computational fluid dynamics, and system-level simulation tools in optimizing design parameters and predicting system performance under variable loading conditions. Key research gaps are identified, including the absence of standardized design frameworks, limited long-term field validation of simulation outputs, and insufficient integration of economic and sustainability assessment within modeling platforms. The review concludes by proposing a multidisciplinary framework that integrates modular engineering design, digital simulation, and sustainability metrics to enhance the implementation of decentralized wastewater solutions in rapidly urbanizing peri-urban regions.

1.1 Global Wastewater Crisis in Peri-Urban Transitions 1.1.1 Rapid Urban Expansion and Informal Settlement Growth Accelerated urbanization, particularly in low- and middleincome countries, has resulted in the rapid spatial expansion of peri-urban areas characterized by mixed land use, informal settlements, and fragmented infrastructure networks. The United Nations estimates that nearly 56% of the global population currently resides in urban areas, with projections indicating continued growth, especially across Asia and Africa (UN DESA, 2022). Peri-urban zones often develop outside formal planning frameworks, leading to heterogeneous settlement patterns and inadequate sanitation provisioning. This transitional geography creates complex wastewater generation dynamics, including fluctuating hydraulic loads and variable organic concentrations, thereby complicating conventional infrastructure planning (Narain and Nischal, 2007). 1.1.2 Infrastructure Lag in Peri-Urban Fringes The expansion of sewerage networks typically lags behind demographic growth due to financial, institutional, and topographical constraints. Centralized sewer systems require extensive capital investment, long conveyance pipelines, pumping stations, and coordinated governance structures. In peri-urban contexts, dispersed settlement morphology and uncertain land tenure further hinder network expansion (Massoud, Tarhini and Nasr, 2009). As a result, a significant proportion of wastewater in these regions remains untreated or partially treated, contributing to environmental degradation and groundwater contamination.

Key Words: Decentralized wastewater treatment, Hybrid modular systems, Peri-urban sanitation, Process simulation, Sustainable infrastructure, Wastewater system design

1.1.3 Limitations of Centralized Sewerage Expansion Centralized wastewater treatment plants are designed under assumptions of stable influent characteristics, high population density, and economies of scale. However, periurban settlements often exhibit low-density clusters and inconsistent wastewater flows, rendering centralized

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