Design considerations and solutions in rapid-prototyping an ultraviolet reactor for ice borehole disinfection

Abstract

Antarctic subglacial lakes are of great interest to the science community. These systems are considered to be in pristine condition, potentially harbouring an environment containing undisturbed sedimentary sequences and ecosystems adapted to cold oligotrophic environments in the absence of sunlight. Gaining access to subglacial lakes presents major technological challenges. To comply with conventions covering the exploration of pristine Antarctic environments, access should be conducted so the lake is not contaminated in any way. Consequently, all equipment to enter the lake must be sterile and the entrance should isolate the lake from the external environment. Currently, clean access to these environments is achieved using a hot-water drilling system. Differences between the hydraulic pressure head of the lake and the glacial surface result in a section of the borehole being air-filled. It is imperative that this section is disinfected prior to introducing any sampling equipment. This paper describes the design process involved in rapid-prototyping an ultraviolet (UV) disinfection reactor for achieving this goal. Considerations such as UV output, physical constraints, temperature management, and deployment procedures are assessed. We present a design that addresses these considerations.

Development of a clean hot water drill to access Subglacial Lake CECs, West Antarctica

“…Once the three straight and vertical holes are complete, a UV source (e.g. Keen and Brito, 2014) could be lowered into the holes if the BigRAID drilling process is proven to be insufficiently clean during the test field season. A 30 W, 254 nm source, lowered at 1 m s −1 would provide the required >16 mJ cm −2 as per ANSI/NSF Standard 55–1991, for a >log-4 cell reduction (Siegert and others, 2012) in the 26 cm diameter boreholes.…”

A mini‐corer for precision sampling of the water‐sediment interface in subglacial lakes and other remote aqueous environments

“…It is estimated that the depth of the shaft will be 3000–3250 m and that the top 10% of this will be air‐filled. The instrumented probe that includes the mini‐corer described in this work would be the second object to pass down the shaft after a UV sterilization source has been passed through the air‐filled section (Keen and Brito ). The probe, which includes a video camera and light system for continuously monitoring the area below the probe, will then be lowered on a conducting tether.…”

Probe technologies for clean sampling and measurement of subglacial lakes

“…Once at site, it was envisaged that, post-drilling, the borehole would be sealed from the atmosphere using an airlock through which instrumentation could be docked, the interface cleaned, and then passed without contact with contamination or the atmosphere into the borehole. Prior to deployment of the first probe, the air-filled section of the borehole would be treated with a UV source [16]. This source, or reactor, was designed to pass through the airlock after installation.…”