A device for autonomous accurate measurement of sediment mass in a water sample

Sediment is a major water pollutant causing damage to aquatic ecosystems, clogging waterways, and filling reservoirs. Regulatory agencies like EPA and TDEC want to regulate sediment release from disturbed land uses (e.g., construction, mining, or forestry) by limiting measured discharge, as they do for contaminants from factories or wastewater treatment plants. However, they rather typically settle instead for simply requiring application of pre-approved BMPs applied to the site in a specified manner, because measuring sediment discharge is such a difficult, expensive, labor-intensive, and time-consuming process. In order to require measured sediment discharge, there must be a system that can accurately and easily measure the sediment concentration in a water sample in-situ and in near real time.This project developed a measurement system to accurately quantify a sample’s sediment mass under either gravity-fed or pumped inflow conditions. The system analyzes a 0.5 L sample every 90 s and measures the sample’s sediment mass to within 0.25 g or 5% of the known added mass (whichever is larger) across the range from 1,200 – 120,000 mg L^-1 of sample. Additionally, the data acquisition system stores data in non-volatile memory and supports wireless data transfer while minimizing power consumption.Preliminary testing shows that with human interaction the system can meet the sediment measurement accuracy requirements for sand, silt loam, and clay loam. However, errors introduced by four different elements of current system dynamics prevent the automation of the data analysis and thus total system success. Once optimized through several additional redesigns, the system could provide a significantly-improved method of regulating discharge from construction sites, as well as providing support for general stream or river water quality work.