Costa Rica (1) Water quality (1) Water--Pollution (1) Water (1) Sieges (1) Sewage--Purification (1) Rivers (1) Research (1) Quality of products (1) Pollution (1) Oxygen (1) Oligochaeta (1) Months (1) Indicators (Biology) (1) Indexes (1) Health (1) Chironomidae (1) Chemistry, Physical and theoretical (1) Archives (1) Ability (1) Agua--Calidad (1) Agua--Contaminación (1) Costarricenses (1) Meses (1) Indicadores biológicos (1) Suelo (1) Factores (1) Gestión (1) Salud (1) Quironómidos (1)