Impact of Bioclogging on Peat vs. Sand Biofilters

Abstract

Biological clogging of unsaturated soils is an important process that can lead to the development of a biomat and failure of biofilters used to treat various wastewater streams. Septic beds and peat filters used to treat septic tank effluent are important applications. Several conceptual models have been developed to simulate clogging in saturated soils; however, limited effort has been conducted to develop similar models for unsaturated soils. Different conceptual models have been proposed to simulate biological clogging in unsaturated systems. These models include the impacts of biomass growth on the relative permeability term for unsaturated flow, but limited experimental data have been used to validate these models. In this study, column experiments were conducted to study the clogging process in loose and dense peat, filter media sand, and septic bed sand. Experimental data indicated that the pore structure of the peat, in comparison to two commonly used sands for septic drainage fields, allowed the biomass to distribute itself over a greater depth within the peat biofilter and delayed the formation of a biomat at the surface and eventual clogging of the filter medium.

Biofilm effect on soil hydraulic properties: Experimental investigation using soil‐grown real biofilm

“…Soil biological clogging (or bioclogging, the clogging of porous media by microrganisms and their byproducts) is seen in many engineered systems. Examples include infiltration ponds [ Rice , ], irrigated agriculture (mostly with effluents) [ Aiello et al ., ], sand filters [ Mostafa and Van Geel , ], constructed wetlands [ Suliman et al ., ; Knowles et al ., ], bioremediation systems [ Pieper and Reineke , ; Antizar‐Ladislao and Galil , ; Singh et al ., ], and petroleum engineering systems [ Ezeuko et al ., ; Surasani et al ., ]. Manipulated clogging of porous media, i.e., the promotion of clogging to obtain a sealed soil, was considered several decades ago in geotechnical engineering [see Dennis and Turner , , for a comprehensive list of studies in that direction].…”

Organic Materials Used in Agriculture, Horticulture, Reconstructed Soils, and Filtering Applications

“…However, the development of a bacterial layer at the top surface (i.e., biomat) may lead to a critical loss of efficiency of biofilters. Mostafa and van Geel (2015) showed that the pore structure of peat allowed a better distribution of microorganisms within the filter material, efficiently preventing bioclogging relative to a sand filter. It also showed that the preparation of the peat (loose vs. compact) had an important impact on the efficiency of the biofilters, and hence, on its duration.…”