Hotel Wastewater Green Infrastructure Treatment System, Guánica, Puerto Rico

Problem

On-Site Disposal Systems including cesspools and septic systems are outdated wastewater treatment systems that are still widespread on islands such as Puerto Rico. When over capacity, these unlined systems cause sewage to leach into nearby soils and can potentially contaminate groundwater, causing public health and safety concerns.

Solution

Green infrastructure uses natural ecosystem functions to treat and/or remove contaminated water at the source. The particular solution used here was a vetiver grass rain garden with biochar soil amendments. The vetiver grass has extensive root systems which rapidly uptake water and nutrients, and the biochar provides habitat for beneficial soil microbes to thrive, which also treat the wastewater. Water leaves the vetiver grass through evapotranspiration, and the soil itself serves as a filtration system to underdrain pipes, which direct the treated water downstream.

Implementation

The rain garden was sized according to the hotel's peak water usage. After completing bioengineering design and analysis, 18" of soil was excavated and remediated with biochar and other amendments, we installed piping and planted vetiver grass. We monitored the site for plant health and water reduction over a year, and it was clear that the system was effectively treating the wastewater. The system has now been performing well for more than 7 years.

Outcomes

After a few months of plant establishment, the system achieved zero discharge, with no effluent coming out of the system. All of the wastewater had been uptaken by the vetiver plants and evapotranspired before reaching the end of the system. This project shows the efficacy of green infrastructure and natural processes to treat the wastewater issue facing Puerto Rico and other islands. These cost-effective solutions can be implemented in various applications, and this project serves as a model for future green infrastructure projects.