1. 1
Survey of Microbial Activity in Oil and Gas Produced Waters
I. Introduction
A. Purpose of project
1. Why chemical and biological monitoring is essential for water treatment systems
2. What can be done to make filtration more efficient and less costly
II. Survey of methods used during microbial study
A. Trial organization
1. Equipment failure
2. Continuous Filtration using both low energy microfiltration and nanofiltration
i. What happens to bacterial levels during treatment
ii. What happens to the water chemistry
III. Conclusions
I. Introduction
A. Purpose of project
The removal of hydrocarbons, total dissolved solids (TDS), and total suspended
solids (TSS) using current pretreatment procedures is well documented in many
studies1
. Monitoring bacterial activity however, has not been identified as an
important water component to monitor. The purpose of this study therefore,is to
evaluate the efficiency of membrane treatment in removing or reducing biological
activity in oil field waters. Chemical components related to microbial growth and
biological activity will be monitored to determine if membrane treated water could
still exhibit bacterial growth during storage or use. Results of the study will be used
to plan future field trials of produced water treatment by A&M researchers.
1. Why chemical and biological monitoring is essential for water treatment systems
Current practice does not account for biological activity in operating procedures,
and considers only water volume when administering biocides. Treatment of
water with biocide and corrosion inhibitors for completion activities is estimated
to cost approximately $25,600 per well depending on the quality2
. Even after
treatment, high levels of equipment failures are still encountered in the field.
These failures are attributed to the ineffective dosage of biocides and anti-scaling
chemicals3
. With these efforts,it is hoped that industry will be made aware of the
importance of bacterial concentrations in water and its relation to treatment
efficiency.
2. What can be done to make filtration more efficient and less costly
Filtration technology has been tested in past studies as a treatment option to re-
use raw produced water. Unfortunately, early filtration technologies were
i
designed around municipal and pharmaceutical wastewaters. High levels of
dissolved organics, salts, solids, and biological components make treating this
type of water a challenge. Addressing this problem, technology developers are

2. 2
evaluating the application of a more aggressive pretreatment,which will make
chemical biocide and anti-scaling treatments more efficient and cost effective.
Pre-treatment procedures are generally focused on removing hydrocarbons, total
dissolved solids, and total suspended solids1
Bag and cartridge filters connected
in sequence with oil coalescing filters are generally used in most pre-treatment
procedures to accomplish removal.
II. Survey of methods used during microbial study
A. Trial organization
Trials were broken into three separate experimental filtration runs. Equipment failure
trial was used to demonstrate the changes that may occur in water quality during an
extended period of stagnancy. All information provided in the report for this run will
be identified as “Failure Test”. Trials one and two were designed to demonstrate
water quality during nonstop filtration treatment. All information provided in the
report for these two runs will be identified as “Trial 1 and Trial 2”.
1. Equipment Failure
Water treatment was started during the morning hours around 9:00AM, and
stopped for approximately 1 hour to simulate a minor failure. Treatment was
continued after 1 hour downtime and again stopped at 5PM. Microfiltration
permeate water was collected,sealed, and stored in a cold room (4ºC) for 4 days.
Cold storage was used in an effort to slow bacterial growth to a level that would
still allow accurate quantification after storage. The 4 day downtime was
intended to simulate a major equipment failure. Microfiltration water permeate
water was removed from the cold room and run through the nanofiltration system
to determine if nanofiltration was worth pursuing.
2. Continuous Filtration using both low energy microfiltration and nanofiltration
Water treatment was started during the morning hours around 9:00AM, and was
run continuously until 4:30PM. Again, the purpose of trial 1 and trial 2 was to
determine the efficiency of microbial substrate removal in microfiltration and
nanofiltration processes.
i. What happens to bacterial levels during treatment
Bacterial levels were quantified using the Bactiquant Meter sold by
Mycometer, Inc. Bacterial measurements are based on the metabolism of a
substrate molecule linked to a fluorophore. Fluorescence levels measured as
the Bactiquant number represent a linear correlation to the amount of
metabolically active cells present in solution. Efforts are being made by the
company to develop a cell forming unit (CFU) conversion to make reporting
bacterial numbers easier for their customers. However,all data collected for
this study will be analyzed and described on a biomass basis. Figure 1 below

3. 3
shows bacterial activity during the failure test,and both nonstop filtration
trials.
Figure 1. Biomass levels after treatment with microfiltration and nanofiltration technologies.
Trials 1 and 2 demonstrate good removal of bacterial biomass however, the
failure test does not appear have a large effect on the level of biomass. It was
determined that during the 4 days of storage, bacteria present in the permeate
due to contamination from environmental factors during the treatment
process were able to utilize the nutrients still present in the permeate water.
Treatment of the stored permeate water was only able reduce the biomass to
a level equivalent to the level present before storage. Overall, the failure test
was concluded to be less efficient in removing biomass than trials 1 and 2.
ii. What happens to the water chemistry
Each successive step in the treatment scheme was observed to improve the
water quality of the produced water. However,100% substrate removal was
never achieved due to the heavy biological and chemical loads each raw
produced water started with. Environmental engineers use pH, dissolved
oxygen, conductivity, alkalinity, total hardness,and carbon levels to
determine a system’s ability to support life. Figures 2-4 provided below are
the figures that displayed the most important findings from the study.
0.1
1
10
100
1000
10000
100000
1000000
MF_Raw_Feed Pretreated MF_Permeate NF_Permeate
BactiquantValue(ml^-1)
Failure Test
Trial 1
Trial 2

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Figure 2. Percent removal of total organic carbon after treatment with microfiltration and nanofiltration technologies.
Figure 2 shows that carbon removal was achieved using both microfiltration
and nanofiltration technologies. The increase in the carbon content observed
from the failure test is evidence of microbial activity during storage.
Filtration removes larger humic acid compounds leaving smaller fulvic acids
for microbial metabolism. Filtration activity can also aid in carbon compound
degradation due to the physical separation mechanism that is occurring.
Figure 3. Potential electron donor species present after treatment with microfiltration and nanofiltration technologies.
Figure 3 shows that even after treatment using micro and nanofiltration
technologies, potential electron donor species important for microbial growth
were still present in permeate waters. Figure 4 below shows that potential
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
140.00%
MF_Raw_Feed Pretreated MF_Permeate NF_Permeate
%TotalOrganicCarbon
Failure Test Total Organic
Carbon
Trial 1 Total Organic Carbon
Trial 2 Total Organic Carbon
18.91
0.01
10.0225
1.925.70
10.05
1.37 0.04
0
10
20
30
40
50
60
70
80
90
100
MF_Raw_Feed Pretreated MF_Permeate NF_Permeate
Species(mg/l)
Trial 1 Total Soluble Iron
Trial 2 Total Soluble Iron
Trial 1 Ammonium, Ammonia,
Nitrite
Trial 2 Ammonium, Ammonia,
Nitrite

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electron acceptor species important for microbial growth were also still
present in treated permeate waters.
Figure 4. Potential electron acceptor species present after treatment with microfiltration and nanofiltration
technologies.
III. Conclusions
According to the above findings, it was determined that water intended for re-use in oil and
gas operations should be physically and chemically treated in preparation for storage.
Neglecting to do this could results in abnormally high souring and corrosion rates. Treatment
using a low energy filtration system would reduce microbial biomass and increase the
effectiveness of initial biocide treatments.
As mentioned before,microbial substrates were found to still be present at a level that could
support opportunistic microbes that may contaminate treated waters during operational use.
In order to deter microbial growth, a residual biocide level should be maintained in all stored
oil and gas waters intended for re-use in hydraulic fracturing activities.
1
. David B. Burnett, F. M. P., and Carl J. Vavra, Achieving Water Quality Required for Fracturing Gas Shales: Cost
Effective Analytic and Treatment Technologies. In SPE International Symposiumon Oilfield Chemistry Society of
Petroleum Engineers: The Woodlands,TX, USA, 2015; p 17.
2. 2015 Well Cost Study Canada, 04/30/2015, 2015; p 70.
3. S. Sherman, D. B., and S. Kakadjian, Microbial Influenced Corrosion of Coil Tubing Milling Strings in the Eagle
Ford Shale. In International PetroleumTechnology Conference SponsorSociety Committees of International
Petroleum Technology Conference: Kuala Lumpur, Malaysia, 2014; pp 2-4.
0.73 0.73 0.7375
0.55
0.31 0.33 0.32 0.20
0.04
3.37
2.33
2.61
0.04
0.04 0.04 0.04
2.07
2.72
5.4625
5.72
0.79
2.97
5.37
0
1
2
3
4
5
6
7
MF_Raw_Feed Pretreated MF_Permeate NF_Permeate
0
50
100
150
200
250
300
Species(mg/l)
Trial 1 Manganese
Trial 2 Manganese
Trial 1 Nitrate
Trial 2 Nitrate
Trial 1 Dissolved Oxygen
Trial 2 Dissolved Oxygen
Trial 1 Sulfate
Trial 2 Sulfate