Microbial diversity of septic tank effluent and a soil biomat

Abstract

Microbial diversity of septic tank effluent (STE) and the biomat that is formed as a result of STE infiltration on soil were characterized by 16S rRNA gene sequence analysis. Results indicate that microbial communities are different within control soil, STE, and the biomat and that microbes found in STE are not found in the biomat. The development of a stable soil biomat appears to provide the best on-site water treatment or protection for subsequent groundwater interactions of STE.

FIG. 1.

Shown are typical on-site wastewater system components (A), a chamber system with an open infiltrative architecture (B), and a stone-and-pipe system with a gravel-laden infiltrative surface architecture (C). (Adapted with permission from Infiltrator Systems, Inc.)

FIG. 2.

Bacterial phylum diversity based on rRNA gene clone libraries and the Ribosomal Database Project classification (7). MP9A, gravel-laden architecture test unit (0.5 cm); MP9B, gravel-laden architecture test unit (1.0 cm); MP10A, open architecture test unit (0.5 cm); MP10B, open architecture test unit (1.0 cm); STE; Control, negative control infiltrative surface architecture; and Summary, a compilation of the sequences of all clones used in this study and examined in all environments. Percentages are based on the total number of clones within each sample.