Activities are focused on membrane distillation (MD), integrating MD with forward osmosis (FO) e.g. FO-MD process, and hybrid systems using adsorption desalination (AD), e.g. AD-MED and AD-MD. Research activities are also focused on gaining a better understanding of biofouling in RO processes and developing biofouling mitigation strategies.
DEVELOPMENT OF SMALL-SCALE MULTI-STAGE DIRECT CONTACT MEMBRANE DISTILLATION (MSDCMD) SYSTEMS FOR REMOTE AREAS
PI: Noreddine Ghaffour
Global climate change and variability have a negative impact on water supply and quality in remote areas by reducing availability of water and dilution of contaminants. This will continue to be exacerbated by limited and inadequate water supply, lack of infrastructure and insufficient water treatment. Therefore, seawater desalination markets demand an economically viable system with a small footprint and scale for those regions. Direct contact membrane distillation (DCMD) process has the simplest configuration and potentially the highest permeate flux compared to other configurations. It can also be easily configured in a multi-stage manner to achieve enhancement of thermal efficiency and water production.
At WDRC, an innovative multi-stage direct contact membrane distillation (MSDCMD) module under countercurrent-flow operation has been designed and investigated both theoretically and experimentally. The experimental study for desalination has proved the feasibility and operability of the MSDCMD design. The investigation of a multi-stage DCMD system with three stages was carried out to estimate system performance after which the feasibility of larger number of stages ranging from 10 to 30 would be studied. It is expected that proper configuration of the standalone small-scale desalination plant for remote areas can achieve an attractive and energy-efficient concept for water desalination application.
ADC PLANT AT SOLAR VILLAGE, RIYADH, SAUDI ARABIA
PI: Kim Choon NG
The first worldwide largest adsorption water desalination and cooling plant (100 m3/day) has been successfully implemented by King Abdulaziz City of Science and Technology (KACST) in August 2016. The project was initiated through a collaboration agreement with King Abdullah University of Science and Technology (KAUST), TAQNIA (Saudi Investment Company) and MEDAD TECHNOLOGIES Pte. Ltd. (a Singapore start-up company exclusively holding pending patent rights for this technology). Adsorption Desalination and Cooling (ADC) is a newly invented technology, co-owned between National University of Singapore (NUS) and KAUST. It is currently one of the most promising thermal desalination and cooling technologies, capable of treating direct seawater, brine water and other highly polluted industrial wastewater, with minimum pretreatment required and with very low electrical consumption (below 1.2 KWh/ m3) and low OPEX costs (below 0.40 $/ m3). ADC Plant project is a unique example of new multinational IP commercialization, where the invention by WDRC, KAUST was realized by KACST into a semi-industrial scale plant located in KACST Solar Village and is currently the largest existing adsorption chiller installation worldwide, with a cooling capacity of up to 1 MW and desalinated water production up to 100 m3 per day.
APPLICATION OF OXYGEN SENSING OPTODES FOR EARLY NON-DESTRUCTIVE BIOFOULING DETECTION
PI: Johannes Vrouwenvelder
Biofouling is a serious problem in reverse osmosis/nanofiltration (RO/ NF) applications, reducing membrane performance. Early detection of biofouling plays an essential role in developing adequate antibiofouling strategies. Presently, fouling of membrane filtration systems is mainly determined by measuring changes in pressure drop, which is not exclusively linked to biofouling. Existing direct biofouling detection methods are mainly destructive, such as membrane autopsies, where biofilm samples can be contaminated, damaged and resulting in biofilm structural changes.
Non-destructive imaging of oxygen concentrations is specific for biological activity of biofilms and may enable earlier detection of biofilm accumulation than pressure drop. The aim of this study was to test whether transparent luminescent planar oxygen sensing optodes, in combination with a simple imaging system, can be used for insitu, non-destructive biofouling characterization. Oxygen sensing planar optodes use luminescent O2 dyes immobilized in an oxygen permeable transparent polymeric matrix that can be coated on a surface enabling quantification of the O2 distribution and dynamics. This method enables direct biofouling detection spatially and quantitatively by measuring a decrease in oxygen concentration as a direct correlation to biofilm activity. Aspects of the study were early detection of biofouling and biofilm spatial patterning in spacer filled channels.
Results showed that oxygen sensing optodes could detect biofouling development at an early stage, even when no significant increase in pressure drop was yet observed. Additionally, optodes could detect spatial heterogeneities in biofouling distribution at a micro scale. Oxygen sensing planar optodes allowed better understanding of the biofilm development process enabling identification of regions where the biofilm starts to grow and how it develops with time. Biofilm development started mainly at the feed spacer crossings. The spatial and quantitative information on biological activity will lead to better understanding of the biofouling processes. The outcome of this study attests the importance of in-situ, non-destructive imaging in acquiring detailed knowledge on biofilm development in membrane systems contributing to the development of effective biofouling control strategies.
UNDERSTANDING BIOFOULING WITH OPTICAL COHERENCE TOMOGRAPHY
PI: TorOve Leiknes
Conventional techniques to investigate biofouling involve taking samples by physically breaking up membrane modules and analyzing biofilm build-up. However, this can disrupt the natural processes behind biofouling, such as water flow through the biofilm. Developing in-situ, non-invasive monitoring of biofouling and biofilm formation can help retain this essential data. The properties and characteristics of the biofilm evolve continuously. The kind of biological processes at work and the changes taking place at any given moment, are key to learning how we can work with and ultimately manipulate the process to reduce its adverse impacts.
In collaboration with KAUST’s Visual Computing Center, TorOve Leiknes and his research team are working on ways of capturing images of biofouling processes in situ and have designed and built a system that can be used with various membrane filtration processes (e.g. RO, MD, FO, MBR, among others). A camera mounted on a mechanical arm controls exactly where detailed images are taken around the membrane module. Using optical coherence tomography (OCT) a large amount of data can be collected to create three-dimensional images of the biofilm - a similar imaging technique used to analyze brain scans. Combined with time series monitoring, a four-dimensional system is created to analyze the dynamic evolution of biofilm development. The team aims to examine the microscopic stages of biofilm growth, a process that is incredibly difficult to see and predict. The ultimate goal is to be able to build biofilm sensors that would allow engineers to detect and monitor initial biofouling of membranes and take steps to alleviate it.