Laboratory testing was conducted to determine the feasibility of using surfactants to enhance soil liner performance in animal waste storage ponds and treatment lagoons. The best surfactants are those which substantially reduce saturated hydraulic conductivity, soil moisture diffusivity, and unsaturated soil wetting front penetration, limit nitrate mobility, and do not adversely impact mechanical compaction characteristics. Saturated hydraulic conductivity was measured using falling-head permeability tests. Transient unsaturated horizontal column experiments provided information concerning surfactant influence on soil moisture diffusivity and wetting front penetration. Standard Proctor methods were applied in the study of surfactant impacts on mechanical compaction. Batch tests gauged nitrate mobility in surfactant treated soil.
Three surfactants, one anionic and two cationic, were tested on a sandy loam. The anionic surfactant, sodium dodecyl benzene sulfonate, and one of the two cationic surfactants, polyoxypropylene methyl diethyl ammonium chloride, produced considerable reductions in saturated hydraulic conductivity, soil moisture diffusivity, and unsaturated soil wetting front penetration. With regard to mechanical compaction, the anionic surfactant and other cationic
surfactant, tetradecyl trimethyl ammonium bromide, affected decreases in the optimum moisture content corresponding to maximum dry bulk density. The moisture content range between optimum and the wet value corresponding to 90% or 95% maximum dry bulk density is also much narrower for these two surfactants, thereby increasing the difficulty of compaction in the field. Interestingly, the cationic surfactant having the greatest influence on soil hydraulic properties was not the same as the one having the most substantial impact on mechanical compaction. Batch tests indicate nitrate mobility in the sandy loam is not significantly altered by soil treatment with any of the three surfactants. Overall, the test results support the feasibility of using surfactants to enhance performance of soil liner material.