Page 61 - AJWEP-22-5

Asian Journal of Water, Environment and Pollution. Vol. 22, No. 5 (2025), pp. 55-64.
doi: 10.36922/AJWEP025130093

REVIEW ARTICLE

A critical review of recent dewatering
technologies: Performance and applications

Hari Bahadur Darlami , Ajay Kumar Jha* , and Kshitiz Ghimire

Department of Aerospace and Mechanical Engineering, Pulchowk Campus, Institute of Engineering,
Tribhuvan University, Nepal
*Corresponding author: Ajay Kumar Jha (akjha@ioe.edu.np)

Received: March 27, 2025; Revised: June 17, 2025; Accepted: July 1, 2025; Published online: August 6, 2025

Abstract: Biogas plants play a major role in Nepal’s renewable energy efforts. However, managing the by-product
remains challenging due to its high water content. The high water content increases the difficulty in transporting,
storing, or reusing the material, especially in rural and farming areas. Dewatering provides a practical solution by
removing moisture, thereby transforming the slurry into a drier, more manageable material. This review compares
several dewatering technologies used in agriculture, industry, and wastewater treatment, with a focus on how they
can help manage biogas slurry in developing countries such as Nepal. Various machines, such as screw presses, belt
presses, and centrifuges, as well as novel method including thermally assisted mechanical dewatering (TAMD), are
included in this review. These technologies were compared based on key factors, including moisture removal rate,
energy consumption, nutrient saving, and operational parameters. Results show that TAMD gives the best moisture
removal, whereas screw presses use less energy and keep useful nutrients in the digestate. Low-cost and fuel-free
machines also show potential for small-scale use in rural areas. Despite these options, the data, infrastructure,
and support to apply these technologies widely are still insufficient in Nepal. This paper highlights the need for
improved local research, enhanced policies, and increased investment to enlarge the scale of these systems. Doing
so could help Nepal maximize the value of its biogas plants, providing cleaner energy and enhancing agricultural
productivity.
Keywords: Dewatering; Organic fertilizers; Biodigestate; Sun drying; Total solid; Thermally assisted mechanical
dewatering

1. Introduction biogas plants installed in Nepal. Biogas production is
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an essential renewable energy source, but its adoption
A biogas plant utilizes various organic waste to produce has been declining due to environmental concerns and
energy through natural breakdown by anaerobic challenges in managing the slurry by-product. The
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processes; hence, it stands as one of the most effective slurry generated from biogas plants has high moisture
and sustainable sources of renewable energy. Biogas content, making it difficult to transport, store, and utilize
is the largest contributor to modern renewable energy efficiently. One effective way to address this issue is
resources in Nepal, producing 256,100 tons of oil through dewatering, which reduces the moisture content
equivalent, having a 65% share in renewable energy in and transforms the slurry into a manageable solid-state
the Fiscal Year (FY) 2079/80. Up to FY 2023/24, there material. This process enhances the functionality of the
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are 450,770 domestic biogas plants and 369 institutional slurry for various applications, such as organic fertilizer

Volume 22 Issue 5 (2025) 55 doi: 10.36922/AJWEP025130093