Abstract

The Niger Delta region of Nigeria hosts Africa’s largest mangrove ecosystem but has suffered extensive petroleum hydrocarbon contamination due to decades of oil exploration, production, and transportation activities. Remediation in this region is particularly challenging because of persistent waterlogging, anaerobic sediments, and high ecological sensitivity. This systematic review evaluates remediation technologies applied in mangrove and freshwater swamp ecosystems of the Niger Delta, with emphasis on effectiveness, feasibility, and limitations under wetland conditions. A comprehensive literature search was conducted across major scientific databases for studies published between 1990 and 2023. Forty-eight studies met the inclusion criteria and were synthesized.
Natural attenuation exhibited limited effectiveness, typically achieving only 5–15% annual total petroleum hydrocarbon (TPH) reduction. Individual biological approaches showed moderate performance, with bioaugmentation achieving 40–60% and biostimulation achieving 22–66% TPH reduction. In contrast, combined bioaugmentation and biostimulation consistently demonstrated the highest effectiveness, achieving 74–99% TPH reduction within 60–180 days. Enhanced rhizoremediation using wetland plants such as Phragmites australis, Eichhornia crassipes, and Vetiveria zizanioides further improved remediation outcomes while supporting ecosystem recovery. Chemical and physical methods were constrained by high costs, ecological disturbance, and limited suitability for wetland environments.
Overall, integrated biological remediation strategies represent the most effective and ecologically compatible approaches for petroleum-contaminated Niger Delta wetlands. Sustained funding, community engagement, long-term monitoring, and prevention of recurrent pollution are essential for successful restoration.