Abstract
Abstract
On-site sewage treatment and disposal systems (OSTDSs) are oftentimes used to treat human waste accruing from nearly one-third of the U.S. population. Operation of OSTDS contributes a large fraction of nutrient loads to groundwater aquifers. This article aims to develop and present a new “green sorption medium,” which has not been fully tested before, to be placed in the vadose zone of the OSTDS underground drain fields. This green sorption medium is comprised of recycled materials with “green” implications for nutrient absorption and adsorption. The composition or recipe of the new material mix was derived based on a thorough literature review. Technical coverage of this study includes material characterization, batch isotherm identification, and a microcosm study leading to improve the application potential of these new material mixes. Batch absorption isotherm data was well fitted by the Langmuir and Freundlich isotherm models. Under the hydraulic retention time of 24 h in a laboratory-scale microcosm of unique functional design, removal efficiencies were found significant for all pollutants of concern. Running as a continuous system, the microcosm, filled with the preselected recipes, was dosed with septic effluent containing 1.76 mg L−1 of ammonia, 0.166 mg L−1 of nitrite, 0.352 mg L−1 of nitrate, and 1.498 mg L−1 of orthophosphorus. This study confirmed 55% removal efficiency of nitrates and 89% of phosphorus under a hydraulic retention time of 24 h. With the aid of Langmuir isotherm data, the theoretical life expectancy of the proposed sorption media mix used in the microcosm was estimated to be 1.2 years for phosphorus sorption. Results obtained largely complement current knowledge on the use of green sorption media for nutrient removal. These findings should also elaborate full-scale field studies in the future.
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