Evaluación del uso de los humedales de manglar como biofiltro de efluentes de camaroneras en Yucatán, México

Abstract

An area of mangrove on the coast of Yucatan (Mexico) was used as biofilter for the discharge of effluents from a shrimp farm intensive cultivation during 5 years. In order to assess the functional capacity of mangroves to reduce nutrient loading and suspended matter in the effluent, water quality variable as NO2-+NO3-, NH4+, PO4-3, total suspended solids (TSS), volatile suspended solids (VSS) and chlorophyll-a were determined. Sampling stations were established in the influent, effluent, biofilter and reference sites in both the marsh and in the sea area adjacent to the farm, sampling was monthly. Also the ponds were sampled biweekly to determine the production and loss of nutrients through a mass balance. The water quality results indicated that the NO2-+NO3- concentrations in the influent was higher with 4.69 mg l(-1) compared to 0.56 mg l(-1) registered in the effluent. The NH4+ was 0.11 mg l(-1) and 0.56 mg l-1 in the influent and effluent, respectively. The PO4-3 was higher in the effluent with 0.18 mg l(-1) while in the influent was 0.06 mg l(-1). TSS, VSS and chlorophyll-a increased its concentrations in the effluent from the ponds. According to mass balance effluents exported 359 kg ha(-1) yr(-1) and 42 kg ha(-1) yr(-1) of N and P, respectively. However, despite the load of nutrients and suspended solids in the discharge of the farm, the biofilter mangrove had the ability to retain 44% of the NO2-+NO3-, 55% of NH4+ and 80% of PO4-3 after the effluent passed through mangrove biofilter. This study demonstrates the efficiency of mangroves in retaining nutrients, so that could be considered as an alternative for the treatment of effluents from shrimp farms.