A direct method for measuring adenosine-triphosphate (ATP) in seawater was developed recently, in which commercial reagents are added directly to seawater. However, calibration is required if seawater quality changes (such as changes in salinity, pH, Mg²⁺, Fe³⁺) as the seawater matrix interferes with ATP measurement. In this research, a 0.1 μm filtration process is introduced to eliminate such interferences. In addition, a filter rinsing step with sterilized artificial seawater is proposed to eliminate interference of free ATP. The ATP-filtration method is fast (<5 min), reproducible (VC = 7%), six times more sensitive than the direct ATP-method and correlates (R² = 0.72, n = 100) with intact cell concentration. Microbial ATP concentration measured using the ATP-filtration method and the ATP-direct method were comparable. Microbial ATP measured along the treatment train of a full-scale seawater reverse osmosis (SWRO) plant decreased from 530 in the raw seawater to 10 ng-ATP/L after pre-treatment and to 0.5 ng-ATP/L in the SWRO permeate. The method was also applied to monitor bacterial growth potential (BGP) across the pre-treatment train of a (pilot) seawater desalination plant, where the removal of BGP through the media filtration and ultrafiltration was 44% and 7%, respectively.

The main source of potable water in high water-stress areas is commonly produced in brackish and seawater desalination plants. Owing to the presence of high concentration of suspended solids, organic matter and colloidal particles in raw water, pretreatment processes are needed for a stable operation of desalination plants. A submerged membrane ultrafiltration pilot plant has been operated as pretreatment of complex brackish surface water to study the filtration performance. The results show the membrane performance, chemical reagent requirements, water quality and cleaning procedures efficiency of an ultrafiltration pilot plant used as pretreatment for a reverse osmosis system. Alternative chemical cleaning procedures have been satisfactorily implemented, which maximize permeability recovery and allow a stable operation.

Controlling fouling in seawater reverse osmosis and ultrafiltration systems is a major challenge during algal blooms. This study investigates UF fouling potential of four marine algae and their algal organic matter (AOM): Chaetoceros affinis (Ch), Rhodomonas balthica (Rh), Tetraselmis suecica (Te), and Phaeocystis globulosa (Ph). Batch culture monitoring of the four different marine algal species showed remarkable differences in their production of biopolymers, transparent exopolymer particles (TEP) and their membrane fouling potential (MFI-UF_{10 kDa}). MFI-UF_{10 kDa} was linearly related to biopolymer concentration, and TEP during the growth and stationary/death phase of all four algal species. But the linear relation of MFI-UF_{10 kDa} with algal cell density and chlorophyll-a concentration did not continue during the stationary/death phase. In experiments with capillary UF membranes, non-backwashable fouling of UF membranes varied strongly for the four different AOM solutions tested, and was linked to the presence of polysaccharides (stretching-OH) and sugar ester (stretching S˭O) groups in the AOM. The non-backwashable fouling coincided with MFI-UF_{150 kDa} and TEP concentration. Therefore, determination of these parameters (MFI and TEP) and correlating with MODIS satellite data may generate useful information about the fouling potential of seawater at different locations during an algal bloom.