AccScience Publishing / AJWEP / Online First / DOI: 10.36922/AJWEP026180123
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ORIGINAL RESEARCH ARTICLE

How do contract pig farms impact the quality of the water environment? Evidence from Hanoi, Vietnam

Hoa Bui Phung Khanh1 ,  Huong Le Thi Thu2 ,  Phuong Tran Trong3 ,  Vien Tran Duc1 ,  Sinh Le Xuan4 ,  Son Cao Truong1*
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1 Department of Environmental Management, Faculty of Natural Resources and Environment, Vietnam National University of Agriculture, Hanoi, Vietnam
2 Department of Business Management, Faculty of Accounting and Business Administration, Vietnam National University of Agriculture, Hanoi, Vietnam
3 Department of Geodesy Cartography, Facultyof Natural Resources and Environment, Vietnam National University of Agriculture, Hanoi, Vietnam
4 Department of Natural Resources and Environment, Graduate University of Science and Technology, Vietnam Academy of Science and Technology, Hanoi
AJWEP, 026180123 https://doi.org/10.36922/AJWEP026180123
Received: 29 April 2026 | Revised: 11 July 2026 | Accepted: 13 July 2026 | Published online: 24 July 2026
© 2026 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
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Abstract

The trend of developing intensive livestock farming is becoming increasingly common worldwide. This has a significant impact on environmental quality, especially water quality. This study was carried out in Hanoi to assess the impact of contract farming (CF) in pigs on the water environment. The aim of this study is to demonstrate the actual impact of CFs on surrounding surface and groundwater. A total of 70 contract pig farms were investigated. In addition, wastewater, surface water, and groundwater samples were collected and analyzed for quality parameters. The results showed that contract pig farms had implemented biogas in combination with other treatment methods such as waste separation, composting, and biological ponds/lakes. However, the wastewater discharged from the farms did not meet the standards of QCVN 62:2025/BTNMT. The study also indicated that surface water surrounding the farms was polluted by ammonium (NH4+), nitrite, and phosphate ions in both the dry and rainy seasons. The water quality index was 63.97 points in the dry season and 67.85 points in the rainy season, indicating average water quality. Conversely, groundwater at pig farms remains largely unaffected and in good condition. The average concentrations of both NH4+ and nitrate ion were lower than the permissible limits set by QCVN 09:2023/BTNMT. At the same time, the comprehensive pollution index values for groundwater were 0.16 and 0.15 in the dry and rainy seasons, respectively, indicating that the water quality consistently remained clean. Promoting CFs is necessary, but it must be accompanied by improvements in waste treatment systems and stricter regulations controlling emissions.

Graphical abstract
Keywords
Contract pig farms
Hanoi
Pollution
Groundwater
Surface water
Funding
This study was financially supported by the Environmental task “Developing technical guidelines for the use of livestock wastewater after biogas plant treatment to meet QCVN01-195:2022/BNNPTNT standards for crop irrigation” of the Ministry of Agriculture and Environment of Vietnam.
Conflict of interest
The authors declare they have no competing interests
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Asian Journal of Water, Environment and Pollution, Electronic ISSN: 1875-8568 Print ISSN: 0972-9860, Published by AccScience Publishing
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