# Presentation: 362662

## Combined Ozonation-Nanofiltration for Drinking Water TreatmentB.S. Karnik1, K.C. Chen1, D.R. Jaglowski2,S.H. Davies 1,3, M.J. Baumann2, S.J. Masten1   1  Civil & Environmental Engineering   2  Chemical Engineering &  Materials Science   3 Biosystems & Agricultural Engineering     Michigan State University 

## Chlorination Disinfection Byproducts (DBPs)

- Disinfection byproducts are formed by the reaction of chlorine with natural organic matter.
- The compounds formed include
- trihalomethanes (THMs; e.g., chloroform, chlorodibromomethane, bromoform)
- haloacetic acid (HAAs) (e.g., dichloroacetic acid)
- chloropicrin and dichloroacetonitrile

## Technologies for the reduction of DBP formation

- Enhanced coagulation
- Granular activated carbon
- Membrane filtration
- Alternate disinfectants
- Chlorine dioxide
- Chloramines
- UV radiation
- Ozone

## Ozone

- Ozonation decreases the formation of chlorinated DBPs
- Leads to the formation of other DBPs, including
- ketones, aldehydes, bromate
- biodegradable organic carbon (BDOC)
- In high TOC waters, ozonation
- is expensive
- leads to excessive DBP formation

## Membrane filtration

- Nanofiltration can remove >90% of natural organic matter (NOM)
- Extent of removal depends upon operational conditions, including molecular weight cutoff and water quality
- Problems
- low permeate flux
- fouling
- cleaning of membranes

## Combined Ozonation /Nanofiltration

- Aim is to combine both processes to reduce problems associated with the use of the processes individually
- Ceramic membranes
- resistant to degradation by ozone
- less subject to NOM fouling than many polymeric membranes
- costly compared to polymeric membranes

## Experimental apparatus

## Experimental details

**Membrane**
- TiO2 filtration layer on an AZT (Aluminum/Zirconium/Titanium Oxide) support
-  MWCOs   1 kD, 5 kD and 15 kD
-  pore size  ca. 1 nm, 3 nm and 10 nm
**Experimental conditions**
-  Cross flow filtration – cross flow velocity 1.5 m/s
-  Ozone:  1.0 to 12.5 g/m3 @ 100 ml/min
-  Trans-membrane pressure – 0.21-0.23 bar
-  Temperature – 20**o**C
-  All samples pre-filtered through a 0.45 μm filter

## Water source

-  Lake Lansing (Haslett, MI)
-  borderline eutrophic
-  algal blooms occur in Summer
-  hardness - 150 mg/L as CaCO3
-  high dissolved organic carbon – 8 to 11 mg/L
**Potential for membrane fouling is high**

## Effect of ozone dosageon permeate flux

- Effect of ozone dosageon permeate flux

## Refouling after ozonation

**Notes:**
Mention that work in the literature has shown TiO2 is a catalyst for the degradation of NOM and other organic compounds in the presence of ozone  

## TTHM precursor removalEffect of MWCO

- Filtered raw water – 236  4 g/L

- O3 - 2.5 g/m**3**

**Notes:**
15 kD does not meet DBPR

## HAA precursor removal:Effect of MWCO

- Filtered raw water – 89  5 g/L

- O3 - 2.5 g/m**3**

**Notes:**
All meet DBPR

## Effect of ozone dosage on DBP precursor removal

- 15 kD MWCO

**Notes:**
This slide shows ozone dosage has little effect on THM or HAA precursor removal.  Not too surprising considering the low ozone dosage 

## Ozone DBP removal

- O3 - 2.5 g/m**3**

## Summary – Fouling Studies

- Ozonation at low dosages reduces fouling; if ozone dosage is high enough no fouling occurs
- The reaction of ozone with foulants appears to be enhanced at the membrane surface, presumably due the catalytic degradation of ozone by TiO**2**

## Summary – DBP studies

- The combined process yields better results than for ozone alone
- Lower DBP concentrations are obtained with tighter membranes
- In the range studied, ozone dosage has little effect on THM or HAA precursor removal
- 1 kD MWCO membrane gives good removal for all the DBPs studied; 5 kD gives good removal of chlorinated DBPs

**Notes:**
Is third bullet also true for pH ???