Forced circulation and aeration in the coastal lagoon of Bojorquez, Mexico

The Bojorquez lagoon forms part of the coastal lagunar system of Nichupte on the Mexican Caribbean. Low impact, non-point pollution has been taking place for almost seven years because of the development of the Cancun tourist resort. Poor circulation within the lagoon and small amplitude tidal effects have created stagnant areas that exhibit high nutrient concentrations, particularly in the sediment. The stagnant areas were defined with the help of hydrodynamic modelling and by locating a suction point at their centers of gravity, a solution was designed in which water will be pumped out and released through a series of small water-falls that will serve to aerate it almost to the oxygen saturation point. The water was then discharged near the water-sediment interphase, thus encouraging the biochemical reaction of organic matter. Electricity could be supplied by means of wind driven generators. Biochemical oxygen demand (BOD) and dissolved oxygen (DO) modelling showed a significant improvement of water quality after six months of operation. This was the most economical sustainable solution found. The Mexican National Water Commission (CNA) is currently constructing the system, and monitoring in the forthcoming years will provide valuable information on its performance.