CASE STUDY: PILOT PLANT FOR NITRATE REMOVAL IN GROUNDWATER - - PowerPoint PPT Presentation

• S. Tarre, M. Beliavski, M. Green

Faculty of Civil and Environmental Engineering Technion – Israel Institute of Technology Haifa, Israel

CASE STUDY: PILOT PLANT FOR NITRATE REMOVAL IN GROUNDWATER USING ION EXCHANGE AND BIOPHYSICAL TREATMENT OF THE RECIRCULATING REGENERANT

SWWS ‐ Sept. 2016

• In Israel, about 250 wells are closed = 80,000,000 m3/yr

The Problem:

• Well size = 25 – 100 m3/hr
• In Israel, high nitrate concentrations in groundwater is

the main reason for closing wells in the coastal aquifer.

• The technologies for nitrate removal fall into two

categories: physico‐chemical processes and biological processes

• Physico‐chemical processes (ion exchange, R.O.,

electrodialysis) were the preferred method. Main problem is the brine produced ‐ difficult to treat and dispose

Options for Nitrate Removal from Groundwater:

• Biological process (denitrification). Disadvantages are

the intensive post‐treatment required and stringent health regulations.

Proposed Solution :

Combined ion exchange and bio‐regeneration process

• Nitrate is separated from the water by Ion

Exchange (IX).

• Exhausted IX column is regenerated by brine

solution recycling with a denitrifying reactor Advantages:

• Almost zero brine and wastewater discharge
• Separation of the biological treatment from the

water supply

Combined System Scheme:

Adsorption phase

Raw water Product water

Regeneration phase

NO3 Selective IX resin

IX

NO3 rich brine NO3 free brine Waste brine disposal Biological denitrification (NO3 ‐> N2) + Post‐ treatment

Process Objectives: First investigated by Van der Hoek and Klapwijk, 1987; Clifford and Liu, 1993, 1996

Combined Concept is not ‘new’:

Still not implemented on at full scale. Combined process problems:

• Relatively complicated vs other processes
• Poor quality of recycling regenerant brine: high DOC, high SS

requiring frequent replacement , resin contamination

• Still ion exchange, high chloride addition to product water and

wastewater from resin washing  Minimize chloride addition to water supply  Improve recycling brine quality for extended use  Minimize brine production  Minimize IX column bacterial contamination

Ion exchange columns – to adsorb nitrate from water Sequential Batch Reactor – to remove nitrate from brine

Pilot Plant Combined System Components:

Ozonation – for brine polishing and recycling

• Minimize Cl‐exchange for NO3

‐ to 1:1, however

• Water also contains HCO3

‐ and SO4 2‐ ions that can be

exchanged, significantly increasing product water Cl‐

• The solution is to use a “Nitrate Selective” IX resin and

extend length of ion exchange service cycle till column breakthrough

Minimizing Chloride Addition During Ion Exchange:

Raw and IX Product Water Composition

5 10 15 20 25 30 50 100 150 200 250 300 350 400 Raw Water 160 BV 380 BV 480 BV N-NO3 SO4-S Cl N-NO3 and S-SO4 mg/L Cl mg/L

Raw and IX Product Water Composition

5 10 15 20 25 30 50 100 150 200 250 300 350 400 Raw Water 160 BV 380 BV 480 BV N-NO3 SO4-S Cl N-NO3 and S-SO4 mg/L Cl mg/L

Brine Denitrification: Improving SBR Effluent Quality

• Ethanol was used as the electron donor
• Ethanol dosage critical for SBR effluent quality
• The solution was to supply the necessary amount of

ethanol by sequential dosing and ORP monitoring and control

• HCl added to maintain pH~8.2 and Cl‐compensation

SBR Control

50 100 150

• 400
• 300
• 200
• 100

100 1 2 3 4 5 6 7 8 N-NO3 mg/L ORP mV Time (hours) 65% % EtOH dosage

SBR Control

50 100 150

• 400
• 300
• 200
• 100

100 1 2 3 4 5 6 7 8 N-NO3 N-NO2 mg/L ORP mV Time (hours) 65% % EtOH dosage

SBR Control

50 100 150

• 400
• 300
• 200
• 100

100 1 2 3 4 5 6 7 8 N-NO3 N-NO2 ORP(mV) mg/L ORP mV Time (hours) 65% % EtOH dosage 10% 10% 10% 5%

• Near 100% suspended solids removal
• SBR effluent has high turbidity, poor filterability and

high bacterial counts.

• DOC of 40 mg/l requiring IX column disinfection
• Minimal waste production due to foam

formation and separation

• High turbidity reduction from 30 NTU to 1~3

Improving Poor SBR Effluent Quality (con’t)

The solution was Ozonation for sustainable regenerant recycling

5 10 15 20 25 30 35 40 30 60 90 120 150 Turbidity - NTU Time - Min Ozone Treatment of SBR Effluent

Minimization of waste brine for removal:

Sources of waste brine and wastewater in the system

IX columns flush of H2O2 Disinfectant; EC=1.1 0.96 BV Sewage Disinfection Waste 1st fill; EC=28 0.66 BV Truck Disinfection Drain 2nd fill; EC=1.4 0.89 BV Sewage Regenerant Waste; EC=57 0.28 BV Truck

0.4% wastewater 0.2% waste brine

Tzur Moshe Pilot Summary:

• Chloride increased from 84 to 121 mg/L
• Nitrate was reduced from 95 to 31 mg/L as NO3

‐

• No increase in product DOC; low bacterial counts
• Competitive price $0.35/m3
• Pilot Plant operated for 1 yr; regenerant not replaced
• 99.4% water recovery

Thank you!