Dr. Veer Kulkarni

Excludes commercial-in-confidence projects.

Research outputs for the last seven years are shown below. Some long-standing staff members may have older outputs included.

Open access indicates that an output is open access.

Journal Articles

Water Engineering: 

"Development of novel design drinking water distribution system pilot plant for simulation of ongoing microbiologically mediated monochloramine decay & investigation into the potential of zinc for decay control"

1.      The major factor of this study was the robust and reliable operation of the novel PDS (consisting of DS-1 control rig, DS2- experimental rig). The semi-passive PDS (single pass, plug flow reactor system) was continuously operated for more than five and half years in an outside environment (exposed to South Australian climate conditions including very hot summer, cold winter temperatures) with minimal supervision and encountered no major problems such as pipe cracks, disconnections, external leaks and blockages.

2.      The 900 m PE pipework provided sufficient surface area and distance (to achieve consistent long HRTs) that helped develop biofilm consisting of nitrifying bacterial community commonly found in large drinking water distribution system pipes. For this study, no microbial culture from outside sources was needed or used. The PDS consistently showed chemical (pH and nutrients), physical (temperature) and most importantly microbiologically (nitrifying bacteria) mediated monochloramine decay in DS1 and DS2.

3.      The extension tank (that received DSs outflows i.e. product water at 900 m of the PDS) consisting of PE pipework with in-line cartridges for the biofilm development provided a convenient platform for microbial sampling.

4.      Before the implementation of online Zn dosing trials, the antimicrobial property of Zn was successfully confirmed (Chapter 5) through a range of Fm experiments and tests. Low doses of Zn (≤ 3 mg/L) were found to be effective in controlling microbiologically mediated monochloramine decay in PDS water samples. Effect of exposure time of Zn at 3 mg/L (i.e. no delay and 24 delay) on microflora and monochloramine decay rate showed no difference. This indicated that addition of Zn into PDS sample waters was equally effective in controlling monochloramine decay rate irrespective of the time delay tested. However, low Zn doses (< 3 mg/L) were found to be ineffective for samples with high Fm values (i.e. high initial microbial activity in PDS water).

5.      The optimum pH at which Zn (up to 200 mg/L stock concentration) remains in aqueous medium (high purity DI water) as Zn2+ is ≤ 6.5. As the concentration rises above 200 mg/L the pH required to maintain Zn2+ species goes down, otherwise Zn2+ precipitates as zinc hydroxide. Also, the potential for precipitation of Zn as zinc hydroxide increases with increase in water temperature.

6.      Under laboratory conditions, NH2Cl residuals were maintained over periods up to 7 days at pH ~7 (± 0.1) and with low Zn2+ (≤ 3 mg/L) concentration in aqueous mediums. This formed the basis for four online Zn dosing trials conducted.

7.      The online Zn dosing trial conducted was successful in controlling microbiologically mediated NH2Cl decay and nitrification which supported the laboratory-scale experiments with Zn. Microflora which had been exposed to NH2Cl for prolonged periods of time, and where microbiologically decay of NH2Cl occurred to high levels, Zn dosing at 3 and then at 6 mg/L, deactivated the microflora. This resulted in recovery of monochloramine residuals at DS2-900 m that lasted for about a 10-week period (without further Zn dosing) in contrast to monochloramine residuals in the control, DS1-900 m. The monochloramine recovery in DS2 coincided with the draining the bulk (external of the pipework) tank water. Minor leaks within the pipework and intrusion of bulk water into the pipework affected the assessment of Zn effect, that led to increasing Zn dosing from 3 to 6 mg/L. The effect of Zn at 3 mg/L was evident on microflora community structure after 5 weeks of dosing but longer periods would be needed to recover monochloramine levels (under the PDS simulated test conditions).

8.      The management of pH during Zn stock preparation, management of flow rates for mixing of Zn stock with treated chloraminated water while maintaining the pH ~7 during actual dosing are the key factors for the consistent release of Zn2+ into treated chloraminated water. Due to low pH effect during Zn mixing and dosing, the NH2Cl levels would reduce overtime. However, the focus should be on Zn2+ release to be effective in deactivation of nitrifying microbes, with maintenance of a required residual.