Across much of Costa Rica, and almost everywhere on the coast, there is no public sewer to connect to. A condo, a hotel, a restaurant, a shopping center or a new residential development has to treat its own wastewater before the water goes back to the ground, to a river or to irrigation. That job falls to a wastewater treatment plant, known locally as a PTAR (planta de tratamiento de aguas residuales).
Ingeniería de las Aguas is an engineering firm based in Palmares, Alajuela. We design, build, optimize and rehabilitate treatment plants for residential, commercial, industrial and urban projects, and we take care of the permits with the Costa Rican agencies involved.
Septic tank or treatment plant?
The first question is whether your project needs a plant at all. Costa Rica draws the line in Decree 42075-S-MINAE, the regulation on disposing of treated wastewater into the ground:
- A septic tank is meant for flows of up to 5 cubic meters per day, which the decree equates to 190 cubic meters of drinking water per month, real or projected.
- Above that, the wastewater must be treated in a system approved under Decree 39887-S-MINAE, the regulation for approving wastewater treatment systems, and the owner files operational reports with the Ministry of Health.
A single-family home is far below the limit, and our page on improved septic tanks covers that case. A condo with several units, a boutique hotel, a restaurant or a group of rentals sharing one system can cross it quickly. A plant is also the answer when the wastewater is not domestic, or when slope, a high water table or lack of space rule out a drain field.
What we do
Design
We start with the real numbers: how many people or units, how much water they use, and what kind of wastewater the project produces. Then we define the most important decision of all, which is where the treated water will go: into the ground through infiltration trenches, to a river or creek with a discharge permit, to irrigation reuse, or to a sanitary sewer if one exists and accepts it. That choice shapes the technology, the permits and the operating cost.
Decree 39887 asks for a design period of at least five years, with growth projections, and allows plants to be built in stages. Its Article 17 also lists elements the construction plans must include, and they are easy to forget in a first budget:
- a two-meter fence or wall with a gate wide enough for a truck;
- flow measurement at the inlet and outlet, and a box for taking samples;
- screens, with at least two sets, and a grit trap;
- a work area for the operator and, in condos and developments, a small building with a full bathroom and shower;
- emergency power when the plant depends on equipment that runs every day;
- lighting, stormwater management and vehicle access.
More about this stage on our design page.
Construction
We build the plant according to the approved plans, coordinate the civil works, equipment and piping, and handle start-up so the system reaches stable operation. A new plant that discharges, reuses or connects to a sewer has three months from the start of operation to file its first operational report, so we plan start-up with that deadline in mind.
Optimization and rehabilitation
Many plants at condos and hotels were built years ago and no longer meet the limits of the Wastewater Discharge and Reuse Regulation, Decree 33601-MINAE-S. Common signs:
- lab results above the limits for BOD, COD, suspended solids or fats and oils;
- odors, foam, sludge escaping with the treated water, or overflows;
- a project that grew while the plant stayed the same size;
- a health order from the Ministry of Health;
- high energy use or maintenance that never ends.
We diagnose each unit, review the lab history and how the plant is operated, and propose what to fix and in what order. Rebuilding everything is rarely necessary. Any remodeling or expansion requires Ministry of Health plan approval under Decree 39887, and we include that filing in the work. See our redesign service.
The permits that go with a plant
A treatment plant goes through several agencies. In short:
- Ministry of Health: a location permit, requested online through the Ventanilla Única de Inversión (VUI). The Ministry has 22 calendar days to resolve it and the permit is valid for two years. Then come plan approval and, for many systems, a health operating permit.
- MINAE, Water Directorate: a discharge permit if the treated water goes to a river, creek or the sea. It is a prerequisite for the location permit. MINAE is Costa Rica's Ministry of Environment and Energy.
- SETENA: environmental approval of the overall project, when the project falls under the environmental assessment regulation. SETENA is the National Environmental Technical Secretariat.
- AyA or the sewer operator: if a sanitary sewer is available, the operator must accept the volume and quality of the water. AyA is the national water and sewer institute.
- Municipality: the building permit for the project.
Our overview of wastewater permits in Costa Rica explains each one, and our permits service handles the filings.
After start-up: operation and follow-up
A plant is only as good as its operation. Decree 33601 requires routine measurements, periodic lab analyses and operational reports signed by a technical professional registered with the Ministry of Health. We prepare operational analyses and reports and follow up on treatment systems. Whoever prepares your reports, ask to see the signing professional's current Ministry of Health registration. If you manage a condo or a hotel, our page on HOA wastewater plant compliance explains the obligations in detail.
Who this is for
- Condominiums and HOAs with a shared plant. If you are buying into one, read our condo treatment plant checklist.
- Hotels and vacation rentals with seasonal peaks. See our guide on boutique hotel wastewater treatment.
- Commercial and industrial sites: restaurants, offices, shopping centers and small industry.
- Urban developments and subdivisions that need a plant, a sewer network and sometimes pumping stations.
We work in Western Alajuela, the Greater Metropolitan Area, Guanacaste, Puntarenas (Central Pacific and Southern Zone) and Limón. See areas we serve.
Tell us about your project
Send us a message on WhatsApp with the location, the type of project, the number of units or rooms and, if a plant already exists, a few photos and the latest lab results. You can also reach us through our contact page.