Enhanced pathogen removal in on-site biofiltration systems over organic filtration materials
Marco A. Garzón-Zúñiga*, Ana C. Tomasini-Ortíz*, Gabriela Moeller-Chavez*, Yolanda Hornelas-Uribe**, Gerardo Buelna*** and Petia Mijaylova-Nacheva*
Mexican Institute of Water Technology. Paseo Cuauhnahuac 8532. Jiutepec, Mor., 65250, Mexico Email: mgarzon@tlaloc.imta.mx Mexico's National University. Institute of Sea Sciences and Limnology. Quebec Industrial Research Centre. 333, rue Franquet, Ste. Foy (Quebec) G1P 4C7, Canada
ABSTRACT
Municipal wastewater was treated in 4 biofilters packed with a mix of endemic tropical woodchips and natural fibers to evaluate the removal efficiency of organic matter and pathogen microorganisms under tropical conditions. Biofilters were operated during 400 days, with a hydraulic rate of 0.3 m3/m2.d and an aeration rate of 0.68 m3air/m2 h-1. Raw municipal wastewater presented higher concentrations, of organic matter and pathogens, than those reported for municipal wastewaters in temperate countries. However, pollutants were successfully removed: <98.5% of the organic matter as BOD5 < 99.99% of Faecal Coliforms (FC) and Total Colony Forming Units (TCFU), and < 96.93% Helminth eggs (HE) were removed remaining only very low concentrations in the treated effluent (≤2.5 mg DBO5/L; ≤ 240 FC/100 mL; ≤ 240 TCFU /100 mL and < 1.0 HE/5L). According with Mexican regulations (Nom 001-SEMARNAT, 1996) and with the EPA suggested guidelines for water reuse (U.S. EPA, 1992a) treated effluents with this quality can be safely reused for three main activities: Nonfood crop irrigation, landscape impoundments and for construction activities. The high removal efficiency of TCFU and FC may be related with a predatory activity of testate amoebas which were detected growing into the biofilters and, the most plausible hypothesis concerning HE removal is that they are retained by filtration over the organic materials.
Keywords: Biofiltration over organic materials; pathogen removal; Helminth eggs; tropical wastewaters; water reuse.
