Laem Phak Bia Royally Initiated Project — Oxidation Ponds, Constructed Wetlands & Mangrove Filtration for Municipal Wastewater (Phetchaburi, Thailand)

In 1990, Thailand's King Bhumibol Adulyadej initiated a research project in Ban Laem District, Phetchaburi Province, to test whether natural systems could treat municipal wastewater while restoring a degraded coastal mangrove. The Laem Phak Bia Environmental Research and Development (LERD) project now covers about 1,135 rai (roughly 182 hectares).
Wastewater passes through a four-stage treatment train: a sedimentation and oxidation pond system, a grass filtration bed, free-water-surface constructed wetlands (two 100 m x 150 m pilot systems were used to compare aquatic plant species), and finally a replanted mangrove forest before discharge to the coast.
University-led monitoring of the mangrove stage found it raises dissolved oxygen by about 32.4% and reduces ammonia by about 73.8% and nitrate by about 64.3%, with final effluent meeting standards suitable for coastal aquaculture.
The project has operated continuously for over three decades under Thailand's Chaipattana Foundation and is used as a long-term research site by Thai universities studying nature-based municipal wastewater treatment; no independent replication of the full four-stage model at another site was found in the sources reviewed.

Read the full analysis: https://www.lerd.org/en/