Miniature Total Organic Carbon Analyzer: Early Development

Abstract

Currently, the International Space Station recovers potable water from a majority of the wastewater sources. Future human exploration missions will also require “closing the water loop” to a high degree because of the expense of resupply and diminishing proximity to Earth. Monitoring the efficiency of removal of organic compounds from wastewater is best carried out using a Total Organic Carbon Analyzer (TOCA). If the Total Organic Carbon (TOC) in the product water is maintained well below potable limits (NASA spacecraft TOC limit of 3 ppm), the need for detailed inflight analysis of specific compounds is greatly reduced. The ISS TOCA has performed well since its activation in November 2008 in conjunction with the US regenerative Environmental Control Life Support System in Node 3. Although appropriate for its current application, the ISS TOCA is too complicated, large and heavy for use on future exploration vehicles and habitats. With NASA-Johnson Space Center Internal Research & Development funding secured, a new effort is underway to develop a highly simplified and miniaturized TOCA, by looking critically at the process steps and developing new ways to miniaturize and integrate the required subsystems. The heart of the MiniTOCA is boron doped diamond coated electrode reactor technology developed by OI Analytical for the ISS TOCA. The current ISS TOCA instrument weighs 34 kg with a volume of 68 L. The goal of the MiniTOCA project is to reduce these characteristics by more than 90%. This paper reports on the early development of the MiniTOCA, and describes some of the challenges encountered. Results of prototype subsystem testing are reported and discussed herein. Progress appears promising toward the goal of developing TOCA technology appropriately sized and robust for Exploration.