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Costa Rica does not have wastewater treatment plants.  Therefore waste management is a domestic operation that every household directly controls and must take into consideration both in the home design and construction process as well as in routine living.  While sewage and grey water are the main interests of this page, solid waste management is also a perennial national challenge, and recycling and waste management initiatives at the national scale remain vestigial and stunted, so for those planning their dream home in Costa Rica, it is important to take a hard look at residential waste management in order to make the best decisions available.

Conventional septic tank / leach field disposal of residential wastewater is well suited to the Costa Rican environment.  Owing to high tropical temperatures and a moist environment, soils are an excellent environment for bacterial degradation of the organic wastes in sewage.  For this reason, a well-designed and build septic system is an entirely adequate and appropriate means of sewage management at the residential scale except in those locations where local circumstances dictate otherwise.  Complete elimination of organic contaminants is often achieved in relatively short distances form leach lines, and adequately sized tanks do not require periodic pumping as even the rate of anaerobic degradation in the primary chamber typically matches or exceeds the rate of sedimentation.  There is nothing wrong with a septic system for domestic and even commercial installations.  There are a few things to look out for.

1)  Poor infiltration.  Soils with high clay content don't allow water to seep into them well.  In the parlance of the trade, these soils "don't perc well."  Percolation tests can determine the size of your system in relationship to the percolation capacity of soils, but in general anything but clay soils will usually provide acceptable results for septic systems.

2)  High water table.  Septic systems are affected by water table level and work poorly when the water table is shallow.  This is the case in swampy and low-lying terrains that are typically complicated by having clay-rich soils.  Right at sea level water tables are very near the surface, so septic systems near sea level often require special considerations.

3)  Separation of grey water and rainfall runoff.  Septic systems should ideally accept water only from toilets.  This reduces the loading on the system and increases its capacity.  Grey water that is from sinks and shower drains is much less contaminated and is optimally passed through a grey water capture and disposal system similar to a septic system but much less involved.  In practice, it is easiest to manage sewage and grey water together in a single septic system. 

4)  Septic tank design.  A dual-chambered septic tank is considerably better than a single chambered tank, and the larger the tank the greater its sedimentation retention and the more likely it is to achieve an equilibrium between solids digestion and solids accumulation.  In general the minimum size supposes a one-day residence time in the tank itself.  But larger tanks provide greater residence and greater solids removal, reducing the burden on the leach field.

5)  Aeration.  To heighten the assimilative capacity of any septic system, the addition of oxygen to force the bacterial assemblage toward a more aggressive aerobic biota greatly increases the efficiency of waste treatment.  This means that an aerator can make a small system perform like a big one.  While this is an indisputable option for optimizing treatment capacity, it comes at a nontrivial expense.  Operation of an air compressor is an energy consumptive activity and septic aerators operate 24/7, so it represents a power sink that can be usually avoided by proper design and operations.

For a no-obligation assessment of how Osa Water Works may be able to assist your waste management planning, please provide us with some preliminary information by filling out the relevant sections of the form accessed by clicking here or write me.



























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