ISS Waste Water Pretreatment Via DNA Pattern Picofilter Using Inorganic Brine Simulant

Astronauts in the International Space Station need as much water as they can access, whether it comes from people's breath, sweat or urine, recycled shower water or from hand-washing. It is of vital importance that any type of water gets recycled and filtrated through different methods so it can be re-used. Recently, a company called Cerahelix, Inc. offered a ceramic tubular membrane element that uses DNA strands as a pattern in a sol-gel process that allows the sintered product to have a pore size in the picometer scale and claims to achieve ten times higher purity than other commercially available ceramic filters. This should allow higher purities and yields at reduced energy costs and theoretically allow near total dewatering of the reject stream and 80%+ polyvalent ion removal. A triplicate set of tests at two different pHs were performed with Cerahelix filters using an inorganic brine simulant in order to test and evaluate the efficiency of its PicoHelixTM membrane and determine feasibility for spacecraft and similar wastewater pretreatment processes. Several ions were studied but emphasis was placed on the polyvalent ions, SO42-, PO43-, Mg2+, and Ca2+; these ions should be rejected almost entirely from the feed solution and, therefore, the masses for the corresponding ions would be as close to zero as the feed permeates through the filter. Initial test results show that at a pH of 4.2, permeation of the polyvalent ions vary from 59% to 74% and at pH of 8.0 permeates vary from 72% to 87%, a very small amount was retained in the reject. Extended Nernst Planck (ENP) approach that describes the mass transfer process in the pico-filtration membranes was used to build a model and be able to explain the experimental outcome.