Wastewater treatment for boutique hotels and eco-lodges in Costa Rica

Boutique hotels, surf camps, yoga retreats and eco-lodges are a big part of Costa Rica's coast, and most of them sit in towns with no public sewer. Their wastewater is treated on the property, which makes the system a core part of the business: if it fails, guests notice the smell before the Ministry of Health does.

This guide explains how Costa Rica's wastewater rules apply to small hospitality projects, from a twelve-room hotel in Santa Teresa to a jungle lodge near Uvita. It covers when a septic tank stops being enough, which permits a treatment plant needs, where the treated water can go, what the reporting looks like and how to deal with the swing between high and low season. For a broader view of each permit, see our guide to wastewater permits in Costa Rica.

Septic tank or treatment plant?

The dividing line is in Decree 42075-S-MINAE, the regulation on disposing of treated wastewater into the ground: 190 cubic meters a month of drinking-water use, actual or projected, which the decree equates to 5 cubic meters of wastewater a day.

• At or below 190 m³ a month: a septic tank or improved septic tank with a drain field can work, designed and documented under Article 7. See how a septic system is sized.
• Above 190 m³ a month: the wastewater must go through a treatment system approved under Decree 39887-S-MINAE. If it is infiltrated, the drain field needs a sampling and flow-measurement box, the treated water must meet quality limits, and operational reports are mandatory (Article 8).

A hotel reaches that line faster than a house. The regulation uses 300 litres of wastewater per person per day for coastal areas, before you add a restaurant, a laundry, pool showers or staff housing. Many boutique hotels end up needing a plant, and it is better to know that at the design stage than after the first full season.

The permits for a treatment plant

Location permit (Ministry of Health)

Every treatment system approved under Decree 39887 starts with a location permit from the Ministry of Health, requested through the investment single window (VUI). The Ministry must resolve within 22 calendar days, and the permit is valid for two years. Then come the construction plans of the plant.

Decree 39887 also asks for elements that cheap designs often skip: a fence of at least two meters with a gate for trucks, flow measurement at the inlet and outlet, a sampling box, screens, space for the operator, emergency power when equipment runs daily, lighting and vehicle access. The plant must be designed for a period of at least five years, and it can be built and approved in stages if the hotel grows in phases. Our treatment plant service covers design and construction.

SETENA

Depending on the size and location of the hotel, the project may need environmental approval from SETENA, the National Environmental Technical Secretariat, under Decree 43898. The wastewater system is part of what that assessment looks at.

Health operating permit

The hotel itself operates under a health operating permit from the Ministry of Health (Decree 43432-S). To renew it, the wastewater reports have to be up to date.

Where the treated water goes

The destination of the treated water shapes the design, the cost and the permits:

Infiltration into the ground. Possible when the soil, slope and water table allow it. A percolation test sizes the field, and above 190 m³ a month the field gets a sampling box and the water must meet the limits in Decree 42075.

Discharge to a river, creek or the sea. Requires a discharge permit from the Water Directorate of MINAE, the Ministry of Environment and Energy, and payment of the environmental discharge fee under Decree 42128-MINAE-S, calculated quarterly on the kilograms of pollutants discharged. For a plant that discharges, the current regulations make the discharge permit a prerequisite for the location permit, so it comes first.

Reuse for irrigation. Treated water can water gardens and landscaping, never be used for drinking. Decree 39887 asks for an irrigation design, a topographic plan, a surface absorption test and at least two monitoring wells, one upstream and one downstream. In Guanacaste, where the dry season runs from December to March and the land gets very little rain in those months, reuse can turn a cost into a resource. More in our guide on greywater and treated water reuse.

Operational reports, explained

Once a plant is running, Decree 33601-MINAE-S, the Wastewater Discharge and Reuse Regulation, requires proof that it works. That proof is the operational report.

• Up to 100 m³ a day of average flow: routine measurements (flow, pH, settleable solids and temperature) every month, lab analyses every six months, and a report every six months.
• Over 100 m³ a day: weekly routine measurements, quarterly lab analyses and a report every three months.
• Seasonal activities that discharge or reuse water five months a year or less file three reports per cycle.
• Reports are due 10 working days after each period closes, and a new plant has three months from start-up to file its first one.

The reports are generated in SIRROAR, the Ministry of Health's online system for wastewater operational reports, and signed by a responsible technician registered with the Ministry together with the owner or legal representative. The hotel must also keep a numbered logbook with daily operation, maintenance, results, incidents and where the sludge went. If you manage a condo or shared plant, our page on HOA plant compliance explains the same duties from the board's side.

Designing for high season

The hardest thing about hotel wastewater in Costa Rica is not the volume; it is the swing. A beach hotel can run nearly full from December to April and half empty in September and October. Biological treatment depends on bacteria that need a steady diet, and a plant designed only for the average can struggle at both ends: overloaded at Christmas, starved in the low season.

Good practice for small hotels includes:

• designing for peak occupancy, with an equalization tank to smooth daily peaks such as morning showers and evening kitchen use;
• modular or staged treatment trains that can run partly in the low season;
• a two-chamber grease trap for the kitchen, cleaned on a schedule, because restaurant grease is one of the main reasons small plants fail;
• separating rainwater from wastewater, so tropical downpours do not flood the plant;
• a realistic operation budget: power for aeration, the operator, lab tests, reports and sludge removal under the national sludge regulation.

Buying an existing hotel

If you are buying a hotel with a plant, the system's paperwork is part of the price. Ask for the location permit, approved plans, discharge permit if any, the operation manual, the logbook and the latest operational reports with lab results. Our due diligence checklist for properties with a treatment plant walks through each item.

How we can help

Ingeniería de las Aguas, based in Palmares, Alajuela, designs, builds, upgrades and rehabilitates wastewater treatment plants and improved septic systems, prepares operational analyses and reports, and manages permits with the Ministry of Health, MINAE, SETENA, AyA and municipalities. We work in Guanacaste, the Central and South Pacific, the Central Valley and Limón; see our Guanacaste page. Tell us about your hotel, its number of rooms, the restaurant and the season pattern on WhatsApp, or through our contact page.