article · Scientific Reports
An evaluation of Lake Manzala, a vital coastal lagoon on Egypt's Mediterranean coast, assesses the success of recent dredging and wastewater treatment efforts across 2021 and 2022. Twelve monitoring stations examined physicochemical metrics, nutrients, and heavy metals. Despite the commissioning of the Bahr El-Baqar wastewater treatment plant and dredging to improve circulation, the ecosystem remains severely degraded. Findings demonstrate a persistent north to south gradient of pollution, with southern areas suffering the highest inputs of organic matter and metals from agricultural and municipal drains. Integrated indices indicate poor to marginal water quality and high heavy-metal pollution stress, with elevated levels of lead, cadmium, nickel, and chromium posing continuous ecological risks. Anthropogenic loading remains the dominant driver of contamination, showing that technical interventions alone have not yet achieved chemical restoration.
Coastal wetlands provide critical ecological and economic benefits, including fisheries and water filtration. When these systems suffer severe pollution, local livelihoods and ecosystems are threatened. This assessment demonstrates that large-scale infrastructure investments, such as wastewater plants and dredging, may not quickly reverse decades of degradation without comprehensive, catchment-wide management and active sediment remediation to lower toxic heavy metals and excess nutrients.
The findings inform environmental engineering firms, municipal authorities, and wetland managers seeking to design targeted remediation projects. The data could support the deployment of specialised sediment treatment technologies and catchment-scale nutrient filtration solutions. Based on the abstract, this research represents applied environmental monitoring rather than a commercial product, serving as baseline operational guidance for ongoing and future remediation programmes.
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Lake Manzala, the largest coastal lagoon along Egypt’s Mediterranean delta, represents an ecosystem of exceptional ecological and socioeconomic significance, yet it has endured decades of severe environmental degradation. This study presents a comprehensive post‑restoration assessment of its water quality during 2021–2022 to evaluate the effectiveness of ongoing dredging and wastewater‑treatment initiatives. Twelve monitoring stations were systematically surveyed seasonally across the lake’s four sectors, and a wide array of physicochemical variables, nutrient salts, and heavy‑metal concentrations were determined. Integrated indices, including the Canadian Water Quality Index (CWQI), Aquatic Toxicity Index (ATI), Trophic State Index (TSI), Pollution Index (PI), and Heavy-Metal Pollution Index (HPI), were applied, alongside multivariate statistical analysis (Principal Component Analysis, PCA) to interpret spatial patterns and dominant controlling factors. Results revealed a persistent north–south gradient of deterioration, with the southern and southeastern sites receiving heavy loads of organic and inorganic pollutants from the Bahr El‑Baqar, Hadous, and Serw drains. The lake remains markedly hypereutrophic; mean BOD5 and COD values exceeded international thresholds, and high concentrations of Pb, Cd, Ni, and Cr indicate serious ecological risk. CWQI values (39–64) classified most areas as poor to marginal, while HPI values (> 180) indicate heavy‑metal pollution stress. PCA distinguished two principal drivers: (1) anthropogenic organic and metal loading, explaining about 52% of the total variance, and (2) natural oxygenation and self‑purification processes with a minor influence. Despite improved circulation from dredging and the commissioning of the Bahr El-Baqar wastewater treatment plant, overall chemical restoration remains incomplete. Long-term recovery requires catchment-wide nutrient control, sediment remediation, and continuous monitoring to restore the ecological balance and sustain the environmental and economic value of this vital wetland.
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DOI: 10.1038/s41598-026-45115-x
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