Sewage outfall plume dispersion observations with an Autonomous Underwater Vehicle

Abstract

This work represents one of the first successful applications of Autonomous Underwater Vehicles (AUVs) for interdisciplinary coastal research. A monitoring mission to study the shape and estimate the initial dilution of the S. Jacinto sewage outfall plume using an AUV was performed on July 2002. An efficient sampling strategy enabling greater improvements in spatial and temporal range of detection demonstrated that the sewage effluent plume can be clearly traced using naturally occurring tracers in the wastewater. The outfall plume was found at the surface highly influenced by the weak stratification and low currents. Dilution varying with distance downstream was estimated from the plume rise over the outfall diffuser until a nearly constant value of 130:1, 60 m from the diffuser, indicating the near field end. Our results demonstrate that AUVs can provide high-quality measurements of physical properties of effluent plumes in a very effective manner and valuable considerations about the initial mixing processes under real oceanic conditions can be further investigated.

Ocean outfall plume characterization using an autonomous underwater vehicle

“…high CDOM) typically having low salinity. It is evident that the core of the plume (highest CDOM values) consists of elevated CDOM levels of approximately 1.3 ppb over the surroimding waters which equate to a minimum dilution of approximately 1:141, Previous work used salinity signatures and inifial mixing lines to estimate dilufion near the diffuser (Washburn et al 1992;Ramos et al 2005). The salinity differences between plume waters and background waters for the 3 March 2011 monitoring mission are approximately 0.05 psu (Figure 4).…”

“…A challenge in accurately tracking a wastewater plume is the design of an effective sampling plan which adapts to variable océanographie conditions in the environment (Ramos et al 2002). For the 3 March 2011 PLOO mission, the most probable missions were planned prior to sampling based on near real-time océanographie conditions at the outfall as monitored by the buoy coupled with plume model predictions.…”

“…Modern techniques using the methods listed above on an Autonomous Underwater Vehicle (AUV) have proven to be a more effective approach for mapping ocean outfall plumes (Wu et al 1994;Ramos et al 2000Ramos et al , 2002Ramos et al , 2007Fletcher 2001) due to their increased spatial resolution, adaptive sampling options, reduced spatial aliasing effects, and low operational costs. This has made them an appealing approach when compared to traditional monitoring techniques.…”

The Role of adaptive mission planning and control in persistent autonomous underwater vehicles presence

“…Examples of mission plan changes might be for a vehicle to search for and then modify its trajectory to follow a characteristic, such as an outfall plume or a thermocline [4]; it might be for a vehicle to have to modify its path to avoid an obstacle, or to search for, find and follow a feature, such as a buried pipeline; or it might be for an action to be taken by a vehicle when a particular value is registered on a sensor, such as the collection of a water sample if the concentration of a particular chemical reaches a certain value, or for fault tolerance [5] [6].…”

Ocean Outfall Mapping Using an Autonomous Underwater Vehicle

“…The recent use of AUVs in a wide range of applications has shown their potential as a mobile sensor in ocean outfall mapping. For ocean outfall monitoring and plume tracking applications, several studies [6] [7] [8] using the REMUS class AUV and one study [9] using the ARCS class AUV have been reported. The paper is organized as follows.…”