Biofouling is undoubtedly one of the major problems affecting the performance of membrane water treatment processes. In fact, membrane flux decline results from a set of combined mechanisms (colloidal fouling, scaling, organic fouling and biofouling), where biofouling is considered to be responsible for 45% of the membrane fouling problems11. As pointed out by Flemming7, the unavoidable presence of a biofilm in any membrane water treatment system becomes a nuisance when it reaches a “threshold of interference”, that is, when it affects the performance parameters (namely, the flux) of the membrane. Therefore, together with the timely detection of this problem, scientists and engineers should aim at reducing the effects of the fouling layer, even if they will not manage to fully prevent it or eliminate it (which is deemed practically impossible).
Some rather recent approaches to water treatment processes for biofouling prevention and remediation, already applied in specific industrial plants, will be incorporated in this study and assessed. These approaches aim at reducing the use of chlorine, due to environmental and health reasons, and controlling the development of biological resistance or adaptation of microorganisms to this biocide, as well as the production of harder polymeric matrices within the biofilm as a bacterial defence mechanism.
Such novel approaches include: a) the use of alternative biocides, mainly those of natural origin, such as plant-based compounds12; b) the incorporation of biocides on the surface of small particles avoiding the loss of biocide carried by the water flow without targeting the bacteria or biofilms, and substantially reducing the amount of biocide wasted in reactions with inorganic material either at the pipe walls or in suspension (particularly suited for water pre-treatment purposes)5,6; c) the enhancement of the activity of biocides (resulting in the use of lower concentrations) by the simultaneous use of physical methods (ultrasounds, pulsed electric field, etc) that are able to disrupt or weaken the bacteria surface and thus favour the chemical attack by the biocide.
The POMACEA proposal will provide improved understanding in membrane technologies and necessary pre-treatment processes for water in India. The project will emphasize the implementation of membrane technologies for water treatment in India according to the following steps (organized in Workpackages – WPs):
1) A feasibility study will be performed in order to understand what are the main challenges for application of membranes for drinking water treatment in Gujarat, Rajasthan and Maharashtra (WP2), involving the collection, characterization, and use of ground and surface contaminated water. In fact, this will allow the generation of a database with the characterization and quantification of the foulants (organic and inorganic), and will allow a more realistic approach to biofouling control and enhanced membrane efficiency.
2) Different water pre-treatment techniques will be tested to evaluate the effect on membrane lifetime (WP3).
3) Reactor systems will be developed to simulate membrane (bio)fouling in lab environment. Real-time monitoring will be performed to study the adsorption of microorganisms on the membranes and the formation of the biofilm (WP4).
4) Membrane cleaning methods will be assessed (WP5).
5) All steps will be combined to build a pilot-plant in India and evaluate the methods developed in the project (WP6).
6) The project activities and results will be disseminated to the policy makers, general public, researchers and entrepreneurs (WP7).