Ph.D Thesis

Ph.D StudentGino Efrat
SubjectPrevention and Rehabilitation of Clogged Wells by
Physicochemical and Biological Treatments as a
Function of Chemical and Biological
Composition of Ground Water
DepartmentDepartment of Civil and Environmental Engineering
Supervisors PROFESSOR EMERITUS Yaacov Mamane


The present research offers a novel approach in clogged well rehabilitation. Microbiological tests of wells from southern area of Israel revealed that the dominant bacterial population is the iron bacteria - Sphaerotilus natans. Chemicals and physical treatment are the methods of choice used in well rehabilitation. The present treatment offers a two-steps treatment: 1. chemical treatment with hydroxyacetic acid, in order to break down biofilm polysaccharide bond; and 2. a new biological approach to infect the dominant free cells biomass with specific bacteriophages.                              

Use of bacteriphages has some important advantages: 1. phages infect bacteria and lyse them releasing more phages; 2. bacteriophages are harmless to humans; 3. highly resistant to chemical stresses; 4. large phages numbers can be obtained easily and at low cost. S.natans bacteriophages used in well rehabilitation will reduce the maintenance cost and prolong its life. A specific Sphaerotilus natans bacteriophage was isolated (ER1) (not reported in scientific literature) and used along the present study.  The virulent ER1 phage was very stable at 200-800C and pH 3-7.5 range and do not adsorb onto stainless steel. Optimal concentration suggested to inactivate any bacterial population (as treatment) is 103-104 PFU/ml for 2-3 days. The efficiency of the treatment proved to be highly efficient. A typical experiment includes glycolic acid addition to remove biofilm from stainless steel surface, then phage addition to inactivate the released bacterial population through infection.

Finally, a correlation was found between biofilm and suspension bacteria, thus allowing future clogging problem prediction (under similar conditions).