Application of Multispectral Images from Unmanned Aerial Vehicles to Analyze Operations of a Wastewater Treatment Plant

Abstract

The main task of a wastewater treatment plant (WWTP) is to reduce pollutants that adversely affect the receiving environment in which the effluent is discharged. The operation of a WWTP is a complex task due to the number of different processes that take place in its process facilities. In order to maintain the high efficiency of a WWTP, it is necessary to control the quality of the effluent at the outlet and monitor the processes taking place there. The main objective of the research presented in this study was to evaluate the possibility of using unmanned aerial vehicle (UAV) technology and multispectral images acquired with a Micasense Red-Edge MX camera to analyse the performance of an activated sludge bioreactor using the example of a municipal WWTP in Poland. Remote sensing analyses were carried out to check the relationships between the calculated spectral indices and the quality parameters in the bioreactor. The spectral indices assessed were the normalised difference vegetation index (NDVI), green normalised difference vegetation index (GNDVI), optimised soil adjusted vegetation index (OSAVI), and their derived indices, after substitution of the red or near-infrared channel with the red edge channel. In this study, the sensitivity of the NDVI and GNDVIRED-EDGE indexes to changes in the nutrient content (NUC) of the bioreactor was observed. The presented research may find application in the design of a new soft sensor for monitoring the operating conditions of wastewater treatment plants.