Sludge Measurement Using Global Positioning System (GPS) Enabled Sonar Equipped Airboat in a Lagoon

Abstract

Proper management of animal waste treatment lagoons requires regular sludge surveys of the lagoons. The traditional manual method of sludge survey is unsafe and time consuming. This article presents the effect of sonar unit variables (sensitivity, noise rejection, and surface clarity) on measurements of top and bottom depth of sludge layer in a lagoon using a GPS enabled sonar equipped (model LCX-15M, Lowrance Electronics, Inc, Tulsa, Okla.) remote controlled airboat. Comparisons between airboat measurements and sludge meter readings and the discrepancy between the measurements from the airboat and an instrument from Remediation Resources, Inc. are also discussed. To study the variables, the top and bottom depth of a sludge layer, position and speed of the air boat were measured using a GPS sensor and an ultrasonic sonar in three situations: 1) Statically at single point; 2) Dynamically along two lines; and 3) Dynamically on a lagoon water surface on a random grid. The top and bottom depth of the sludge layer was also measured using a sludge meter method at several points within the cone area for the static location of the transducer. This preliminary study suggested the use of 25% sensitivity level, an inclusion of a correction factor accounting for speed of sound in lagoon water, the steady movement of the boat and the use of a more accurate GPS system (accuracy within inches with DGPS) for future research to measure sludge within acceptable limits.