טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentGluska Dror
SubjectNitrate Removal by Ion Exchange and Bio-Regeneration
Focusing on Product Water Quality and Waste Brine
Volume
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Emeritus Michal Green
Dr. Sheldon Tarre
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Abstract

   Groundwater is an important drinking water resource, and therefore wells closure due to pollution arouses serious concern, while one of the main pollutants over the last three decades is nitrate. The traditional treatment methods remove the nitrate effectively, but have significant disadvantages, such as large volumes of waste brine (physico-chemical technologies) or requirement for intensive post treatment in order to prevent microbial contamination (biological denitrification). The current study is part of a research program in which a treatment process combining physico-chemical and biological technologies was investigated to remove nitrate from groundwater. This process has the advantage over traditional systems in diminishing brine production while reducing the potential for microbial contamination.

   A pilot system treating 2 m3/day of nitrate polluted water was built to investigate the combined process. First, the nitrate was removed from a simulative water source containing high nitrate levels (25 mgN/L) by ion exchange (IX) nitrate selective resin. After IX column exhaustion, the resin was regenerated with a salt solution containing 15 gCl/L. The regenerant solution was treated biologically to fully remove the nitrate using a denitrifying sequential batch reactor (SBR). Before being reused for regeneration in the following cycle, the regenerant leaving the SBR was passed through a post treatment stage to remove suspended solids and microbial residues. Thus, the volume of waste brine produced in the process was significantly reduced, relatively to traditional IX processes. The current study focused on the IX stage in the combined process, where the main objectives were to maintain low nitrate and chloride ions levels in the product water and to minimize the waste brine production. The research hypothesis was that adsorption phase duration has a significant effect on the treated water quality, specifically in nitrate and chloride concentrations, as well as on the volume of waste brine that has to be disposed.

   Unlike previous studies investigating nitrate removal systems based on a similar principle, this study puts a special emphasis on product water quality.

   The main conclusions of the study are:

-          Using combined system of IX and bio-regeneration for nitrate removal from drinking water has applicable feasibility.

-          For the simulative raw water, treatment cycles of 380BV are optimal. Long cycles are necessary to reduce chloride increase and sulphate accumulation.

-          Waste brine volume is approximately 1 BV/cycle, less than 0.3% respectively to product water volume.

-          Operational costs estimation of full-scale system is lower than 0.24 $/m3.