Examination of particle dispersion when saline concentrate is released in septic tank wastewater

Soil dispersion due to salinization is an important concern associated with the land application of saline wastes. When residual brine is transferred to septic systems, dispersion of sludge can lead to complications, as well. This study investigated sludge and microbial population response of septic wastewater during residual saline application. Salinity concentration up to 10 ppt (‰) was included, within the range of residual saline waters in the region. The dominant salt cations by order of decreasing concentration were Na, Ca, and Mg. The initial heterotrophic microbial population was lowest for all control and treatments in the log 4.5–4.8 cfu mL⁻¹ range. A regrowth period followed towards the end of the experiment commonly reaching log 6 cfu mL⁻¹. UV absorbance was used to quantify dispersion of solids and treatments produced statistically significant differences in absorbance. This work shows the importance of considering the consequences of saline application to waste.