1. Results and Discussion
COD Concentration Over Time MLSS Concentration Over Time
OPTIMIZING BATCH REACTOR SYSTEMS FOR SCALE UP IN THE REMOVAL OF ORGANIC CARBON FROM WASTE WATER
Brian Rojas-Lerena, Dr. Mark Matsumoto, Jose Valle, Brian Luck, Vincent Hoang
Department of Chemical and Environmental Engineering,
University of California, Riverside
Abstract
The bench-scale testing of anaerobic and aerobic reactor systems is being
conducted to determine optimum operating conditions for the treatment of a
wastewater containing high concentrations of organic carbon-based chemicals
found in commercial paint stripers. Paint stripers are commonly used by the
military for changing camouflage purposes. The wastewater generated from
paint stripping causes significant problems for municipal wastewater treatment
systems when it is discharged into the sanitary sewer system. The main goal is
to optimize operating conditions of the reactors for the maximum removal of
these organic-based compounds. The primary metric for measuring their
performance is completed by measuring the chemical oxygen demand (COD)
of the influent and effluent after a 24 hour treatment cycle. In this study, four
batch reactors were operated: two anaerobic and two aerobic. Water quality
parameters monitored in these reactors included pH, dissolved oxygen (DO),
alkalinity, turbidity, and total and volatile suspended solids (TSS, VSS). Both
anaerobic reactors were heated to 35°C to provide favorable bacteria
conditions, while the aerobic reactors were not. Data has shown that the
anaerobic reactors perform at an average 83% COD removal, while the aerobic
reactors perform at an average 93% reduction. These data implicates that the
implementation of a large-scale aerobic reactor, for the purpose of the
maximum removal of these organic compounds, is more suitable.
Introduction
Anaerobic and aerobic batch reactor systems are commonly used for the
treatment process of organic-based compounds found in municipal wastewater.
However, the problem concerning these systems is their biological sensitivity to
changes in the environmental conditions around them. One specific condition is
the introduction of high concentrations of these organic-based compounds
found in painter strippers that are primarily used at a military base in Georgia to
remove paint from their vehicles and aircrafts. Our study is primarily focused on
optimizing the performance of our reactors by utilizing a batch that can be
biologically sustainable under this occurrence. Our research will be
implemented by the military for the purpose of the degradation and removal of
these compounds, from municipal wastewater, with the use of a large-scale
reactor built based on the results that we have collected.
Methods
My research includes working with 4 reactors: 2 anaerobic and 2 aerobic. The
reactors are numbered 2, 4, 5, and 6.
Reactors 2 and 4 are kept under anaerobic conditions and heated to 35°C.
Reactors 5 and 6 are kept at room temperature and under aerobic conditions
Feeding
A feed is created to sustain and maintain the biological bacteria in each reactor.
The feed contains:
18g of B & B Tritech solution (Benzene Alcohol, Hydrogen Peroxide, Aromatic
Petroleum Distillate)
24g of commercial fertilizer (containing a 10P:10K:10N ratio)
17L of tap water
The feed is stirred using a stir plate and magnetic bar before and during
feeding at 400rpm to ensure a well mixed solution. Before feeding, the reactors
are turned off by an automated timer to allow for a 3 hour settling time for each
reactor. After the each reactor has settled, effluent is extracted from each
reactor and emptied to a certain level. The reactors are then refilled with the
feed back to their appropriate levels. Feeding occurs while the reactors are
mixing to allow for the reactors optimal uptake of nutrients within the feed.
Chemical Oxygen Demand (COD) Test
A COD digester is used for the first part of this test High range (HR) COD vials
are prepared by mixing 2ml of filtered sample from each reactor with solution
containing mercury and acids, such as sulfuric acid. Vials, including one blank,
are incubated for 2 hours before a COD reading can occur. After the incubation,
A DR 1900 Spectrophotometer is used to read the COD from each vial.
Mixed Liquor Suspended Solids (MLSS) Test
An MLSS test is conducted to test for how will the bacteria are degrading the chemical
and how stable the reactor is doing relative to how much concentration is being
accumulated over time. During mixing, sample is collected from each reactor and then
filtered. After the filtration, each filter is heated to 550°C for 30 minutes. The filters are
then weighted. The filters are heated once again, however at 105°C for 1 hour. The
filters are then weighed again.
Water quality
DO, pH, TSS, Turbidity, and alkalinity are water parameters tested to check the quality
of the water in each reactor. DO and pH is tested with the use of a DO meter and pH
probe. TSS is tested by using a filtration apparatus to filter 50ml of sample from each
reactor. The samples are run through their own filters, which are weighed before
filtering. After the samples are filtered, the filters are heated to 105°C for 1 hour, and
then are reweighed. Alkalinity is tested by diluting 25ml of each filtered sample with
diluted sulfuric acid to a pH of 4.3. Turbidity is tested by placing 25ml of unfiltered
sample from each reactor through a turbidity meter.
Filters are pre-heated to 105°C for 1 hour before use.
Current Removal Rates:
Reactor 2 removal rate: 85%
Reactor 4 removal rate: 82%
Reactor 5 removal rate: 92%
Reactor 6 removal rate: 93%
The aerobic reactors are removing COD more efficiently compared to anaerobic removal
rates. This data supports the decision for a large-scale aerobic reactor to be
implemented by the military base in Georgia. The fluctuation in the beginning might be
due to different concentrations of feed being implemented. The reactors have now
reached a stable form.
Acknowledgements
I would like to thank Dr. Matsumoto and Jose Valle for advising my poster material, as
well as for allowing me to work under them to conduct this research. I would like to thank
all the undergraduates as well, whose work contributed to collecting this data: Joanna
Vasquez, Brian Luck, and Vincent Hoang. I would also like to thank NSF, UCR and
CAMP for funding my research.
Most Recent Concentration Levels
Reactor 2: 4180 mg/L
Reactor 4: 8140 mg/L
Reactor 5: 1460 mg/L
Reactor 6: 3680 mg/L
This data shows the concentration levels of each reactor from the specific date the test
was conducted. Levels have fluctuated for each reactor but reactors are stable and
necessary action is taken to ensure the performance of each individual reactor.
Reactor 6
Aerobic
Reactor 4
Anaerobic
Reactor 2
Anaerobic
Reactor 5
Aerobic