Fouling abatement in seawater desalination

Dissolved air flotation (DAF) in combination with ultrafiltration (UF) is gaining attention as a promising pre-treatment to reduce biofouling in SWRO membrane systems, particularly during algal blooms. The operation of DAF is always preceded by coagulant dosing (ferric chloride) to remove algae, organic matter as well as dissolved phosphate. Phosphates are known to form strongly bonded complexes with iron in the wide range of pH (Belelli et al., 2014, Tejedor-Tejedor et al., 1990). The application of UF downstream of DAF further enhances removal of small flocs that pass through DAF systems.
Despite advances in pre-treatment, biofouling in seawater reverse osmosis is still a major problem as neither DAF nor UF are optimized to remove dissolved phosphate or other nutrients. The potential sources of biodegradable compounds such as carbon and phosphate in seawater are: the raw water (presence of algae), chlorination of the raw water, and contamination of chemicals used in desalination plants. In this study, we will develop a method to measure low levels of ortho-phosphate in RO feed water for seawater & freshwater (<0.3 μg PO4-P /L). Then, the research will demonstrate and optimize the possible role of DAF and UF (with coagulation) in removing phosphate and other nutrients and reducing bacterial regrowth potential (BRP) in SWRO systems.
The research objectives are the following:
i) Develop a method that can detect low levels of ortho-phosphate (target ≤ 0.2 ppb) in freshwater and seawater;
ii) Optimize DAF and UF systems in reducing ortho-phosphate and bacterial regrowth potential prior to SWRO membranes systems;
iii) Quantify the role of chemicals used in SWRO in enhancing bacterial regrowth in desalination plants;
This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 606838, with additional support from IHE Delft.

Duration: 2 years
Post-doc: Dr. Mamoun Althuluth

   

Investigation into Fouling at FEWA Desalination Plant

The Federal Electricity & Water Authority (FEWA) seawater desalination facilities located in Ghalilah, Ras Al Khaimah, United Arab Emirates have been in operation since early 2015 and supply drinking water to the municipalities. The purpose of this work was in a short period of time: i) to assess the operation performance of the plant and to give suggestions for improvement; ii) to recommend further actions e.g., collecting/analyzing more detailed operational data, and additional tests.

Period: September-November 2016
Location: Ras Al Khaimah, UAE
Client: Pentair (Netherlands)
Staff: Dr. Maria Kennedy, Dr. Sergio Salinas
Partner: Schippers Water Treatment Consultancy
PhD student: Nirajan Dhakal

Zero Chemical UF/RO Desalination System

The project focuses on reducing chemical consumption through optimizing coagulation conditions for production of drinking and industrial water from salt and brackish waters (project partners: Pentair X‐Flow, Vitens, Evides, University of Twente, and University of Aachen).

Donor: SenterNovem
Partners: Pentair X‐Flow, Vitens, Evides, University of Twente, and University of Aachen
Duration: 2009 – 2014
IHE staff: Maria Kennedy
PhD student: Assiyeh Tabatabai

Reuse: Producing ultrapure water from domestic wastewater

Synthetic organic polymer fouling of reverse osmosis membranes

In water treatment synthetic organic polymers play an essential role. Severe irreversible fouling of reverse osmosis (RO) membranes due to these synthetic organic polymers is reported. Unfortunately, these synthetic organic cationic polymers are in many situations the most effective or the only effective polymer type. This situation is a real threat for the further expansion of waste water reuse making use of RO systems and a danger for large (and small) scale sea water / river water desalination based on reverse osmosis and making use of conventional pre-treatment systems (coagulation / sedimentation, flotation, media filtration).

This threat and danger is severe since knowledge on fouling potential, tools monitor and to develop mitigation measures are lacking e.g.,
• Currently is it not known whether all types of synthetic cationic polymers are causing severe irreversible fouling.
• It is not known whether alternative polymers (non-ionic and anionic) are available which are effective but don’t foul RO membranes.
• Analytical methods are not available to measure the concentration of cationic polymers in feed water of RO systems. A complication factor is that these polymers use the have a wide range molecular mass. As a consequence operators have no tool to dose the polymers accurately to avoiding overdosing and/or adapting process conditions.
• Mitigation measures e.g., pre-treatment processes are not developed or not tested and current chemical cleaning methods are not effective in most cases.

Sponsor: NieuWater (Netherlands).
Duration: 2 years, 2012-2014.
Budget: 24k euros.
IHE staff: Jan Schippers, Sergio Salinas, Maria Kennedy
Research fellows: Yuli Ekowati, Madiany Hernandez

Algal Blooms and membrane desalination systems

The goal of this study is to understand the adverse impact of seawater algal bloom on the operation of UF and RO membrane systems. Furthermore, this study aims to develop/improve methods to investigate the characteristics and the membrane fouling potential of algae and algal organic matter (AOM). The ultimate goal is to provide engineers/operators with a better understanding as well as reliable assessment tools to develop robust processes and effective operation strategies to maintain stable operation in membrane-based desalination plants during an algal bloom.

Donor: Wetsus
Partners: Pentair X-Flow
Duration: 2008 – 2014
IHE staff: Maria Kennedy, Jan Schippers
PhD student: Loreen Villacorte