INVESTIGATION OF BEACH SANDS FOR USE IN CONSTRUCTED WETLANDS IN AKUMAL AND TULUM, QUINTANA ROO, MEXICO

Constructed wetlands are ecologically based technologies that have been widely used to treat domestic wastewater in developing countries. A major driving factor in the implementation of these systems globally is the low economic cost and low technical background of users needed for operation. Constructed wetland systems have been widely implemented in the Akumal region on the eastern coast of the Yucatan, a major tourist region. These systems have been regarded as being moderately successful over approximately 10 years of operation. Despite the success of the systems, wide scale implementation throughout the Yucatan has not occurred. Several issues are believed to contribute to the lack of broad use however one major factor is cost of installation. One large cost in the systems is that of aggregate.

Beach sand is a promising alternative aggregate because they have little or no cost. Geologic properties of beach sands from the Akumal region and the Tulum region were investigated. Sands have permeability coefficients that vary from approximately 0.006 cm/s to 0.012 cm/s. The grain size distribution of samples typically varies from 5.0 mm to 38 micrometers. Distributions are unimodal with modes commonly being between 0.3 mm and 2.0 mm. Scanning electron microscopy (SEM) investigation indicates sand particles are commonly porous and are irregularly shaped. Forams and diatoms are common several samples. Some sands have significant coatings of diatoms which may be beneficial in absorption of some pollutants.

Implementing the sands for use in constructed wetlands is recommended. The beach sands provide a higher surface area compared to current crushed aggregate gravels used in constructed wetlands. The porous nature of the sand grains may be beneficial in providing more substrate for microbial communities. Care should be taken in using sands however so as not to disturb sea turtle nesting sites.