Pairing of Anaerobic and Aerobic Treatment of Petroleum Wastewater

27 Pages·2017·7.74 MB·English

Utah State University
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All Graduate Theses and Dissertations Graduate Studies
5-2017
Pairing of Anaerobic and Aerobic Treatment of
Petroleum Wastewater
Zachary Fica
Utah State University
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PAIRING OF ANAEROBIC AND AEROBIC TREATMENT OF
PETROLEUM WASTEWATER
by
Zachary Fica
Thesis submitted in partial fulfillment
of the requirements for the degree
of
DEPARTMENTAL HONORS
in
Biological Engineering
in the Department of Biological Engineering
Approved:
Thesis/Project Advisor Departmental Honors Advisor
Dr. Ronald C. Sims Dr. V. Dean Adams
Honors Program Director
Dr. Kristine Miller
UTAH STATE UNIVERSITY
Logan, UT
Spring 2017
Zachary Fica
Honors Thesis Acknowledgements
I would like to acknowledge The Sustainable Waste-to-Bioproducts Engineering Center, State of
Utah Water Research Laboratory, Huntsman Environmental Research Center, USU Caine Dairy, USU
Department of Biological Engineering - Reece Thompson, Terence Smith, Jonathan Wood, Alexa Lunt,
Maureen Kessano, Alan Hodges, Jordan Wanlass, Tyler Marlar, Justin Mariott- Dr. Ronald Sims, Dr.
Judith Sims, Dr. Charles Miller.
Thank you for all of the support and guidance.
UT AH ST ATE UNIVERSITY
Logan, UT
Spring 2017
Contents
Project Summary ........................................................................................................................................... 3
lntroduction ......................................................................................................................................... .......... 3
Objectives ....................... ............................................................................................................................... 6
Evaluation Criteria ......................................................................................................................................... 6
Background .................................................................................................................................................... 7
Current Petroleum Waste Water Strategies ............................................................................................. 7
Fundamental UASB Concept ..................................................................................................................... 9
UASB Organics Reduction .................................................................................................... ...................... 9
Solids in UASB Treatment.. ............................. ................................................................ ......................... 12
UASB Limitations ..................................................................................................................................... 12
Algae-Based Treatment of Petroleum Wastewater .......................................... ...................................... 13
Rotating Algae Biofilm Reactor (RABR) ....................................................................... ............................ 13
Design Process ........................................... .............................................................. .................................... 14
Overview ................................................................................................................................................. 14
Rationale and Decisions .......................................................................................................................... 14
Methods ....................................................... ........................................................................................... 15
Final Design Review .................................................. ................................................................................... 17
Experimental Results ............................................................................................................................... 17
Final Design ..................................... ........................................... ............................................................. 19
Conclusions ............................................................................. ..................................................................... 19
Recommendations for Future Work ........................................................................................................... 19
References ................................................................................................................................................... 20
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Pairing of Anaerobic and Aerobic Treatment of Petroleum
Wastewater
Project Summary
The objective of this project was to treat petroleum refinery wastewater using a combination of anaerobic
and aerobic processes, namely an Up-flow Anaerobic Sludge Blanket (UASB) reactor paired with a
Rotating Algae Biofilm Reactor (RABR), respect ively, to produce a treated effluent. The treatment
method developed needed to produce a cost-effect ive and efficient way to decrease nitrogen , phosphorus,
total suspended solids (TSS), and COD concentrations to below State of Utah limitations. It was
demon strated that RABR treatment was capable ofreduc ing effluent concentrat ions of nitrogen,
phosphoru s, and TSS to State of Utah limitations. RABR treatment did not significantly reduce COD
from the wastewa ter. The COD reduction requirement, however, was met through anaerobic digestion of
the wastewater. Therefore, our system proved effectual at the treatment of the wastewa ter and met all
design criteria.
Introduction
Petroleum refining accounts for the production of a large amount of wastewater , approx imately 33.6
million barrels per day (mmpd) globally (Diya·uddeen et al., 2011 ). Though nature has the capability to
treat or cope with small amounts of wastewater and pollution , it would be overwhelmed if billions of
gallons of wastewater were left untreated. Treatment strategies reduce pollutants in wastewaters to levels
that nature can handle .
Sources of wastewater contain many xenobiot ic compounds. heavy metals, and a high solids content,
resulting in waste that is difficult to treat using many current methods (Knight et al., 1999). There are
many effects of wastewater pollutants, but the following are of major concern. When the dissolved
oxygen in bodies of water drop, fish and aquatic biota, or other plant and animal life in that habitat,
cannot survive. Those suspended solids also increase turbidity , which blocks out sunlight and reduces the
rate of photosynthesis, smothering ce,tain habitats (Perlman, 2015).
When left irntreated, wastewater can contain excess nutrients , such as phosphorus and nitrogen, with large
quantitie s of ammon ia. These excess nutrients can cause eutrophication, or over-fe,tilization of receiving
waters. Genera lly, this is toxic to aquatic organisms, promotes excessive plant growth, depletes or reduces
available oxygen, harms spawning grounds, alters habitats and leads to a decline in certain species. In
addition, chlorine compo unds and inorganic chloramines, which exist in untreated wastewate r, can be
toxic to aquatic invertebrate s, algae, and fish. Heavy metals, such as mercury, lead, cadmium, chromium
and arsenic can also have acute and chronic toxic effects on species (Environment and Climate Change
Canada, 2014 ).
Petroleum refinerie s process raw crude oil into three different categories of products, namely fuel
products, nonfue l products , and petrochemicals or petrochemical feedstocks. For these categories, the
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method s required to process the crude oil are topping, thermal and catalytic cracking, combining or
rearranging hydrocarbon s, removing impuritie s such as sulfur, nitrogen and metals, and specialty product s
blending and manufacturing.
Topp ing is the process of separatin g crude oil into hydrocarbo n groups, by desalting, atmosphe ric
distillation , and vacuum distillation. Therma l and catalytic reforming breaks the larger, heavier
hydrocarbons received from topping into smaller hydrocarbo ns (Figure 1) .
,-,,.-~_ J
·I ( " reformate .~ .
feed pre-treater • \ reactor ) fractionator I
(naphtha) •• I ,. ..
~
hydrogen
- -
- ----
---
--
compressor
------
Figure I. Diagram of the catalytic reforming process (U.S. EIA, 2013).
The reforming process uses heavy naphtha, which is the second lightest liquid stream from an
atmospheric distillation column, to produce reformate. Reformate is a compone nt of finished gasoline.
Because reformate conta ins significant amounts of benzene , toluene, and xylene, it also is an important
source of feedstock for the petrochemica l industry. One of the byproducts ofrefonni ng is hydroge n,
which can itself be used in other refining processes or sold for other industrial use (U.S. EIA, 2016).
Coking is a refinery unit operatio n that upgrades material called bottoms from the atmospheric or vacuum
distillation column into higher-value product s and, as the name implies, produce s petroleum coke, a
materia l similar to coal. Two different types of coking processes exist: delayed coking and fluid coking
(Figure 2).
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Delayed Coking Fluid Coking
r •••. , ·----- •
~ ~
::, ::,
a: a:
C 0
w \U
X X
0 0
u u
........__
RcJctor
i Furnace
-- +----R-e-c-v-c-!-e -.
•. , H~'lYY
Fc :,:(, d1ct;11'1'11:'
Figure 2. Processes of coking (U.S. EIA, 2013).
Both delayed and fluid coking are physical processes that occur at pressures slightly higher than
atmospheric and at temperatures greater than 500°C that thermally crack the feedstock into products such
as naphtha and distillate, leaving behind petroleum coke (U.S. EIA, 2013).
Petroleum refineries have many wastewater streams coming from processing. Desalter , sour, and other
process wastewater make up the majority of the wastewater streams. Desalter wastewate r is produced
from wash ing the raw crude oil prior to topping operat ions. Sour water is created from steam stripping &
fractionating operat ions that come into contact with the raw crude oil being processed. Other process
wastewate r comes from product washing, catalyst regeneration , and dehydrogenation reactions (US EPA,
2016).
The combination of the UASB reactor treatment and the RABR treatment could potential ly be a cost
effect ive and efficient way to decrease BOD, COD, phosphorous, and nitrogen. Research has shown that
UASB is an effective treatment for COD removal; however , reductio n of BOD, nitrogen , and
phosphorous are often not reported (Rastegar et al., 201 1) . Rotating biological contactor (RBC) treatment
has been studied for petroleum refinery wastewater and shown to decrease COD and phosphorous
(Chavan et al., 2008). There have been limited studies on rotating biological contactor (RBC) treatment
of petroleum refinery wastewater using algae and no studies were found using UASB and RABR in
combination, making this treatment an innovative approach. Biomass recovered from RABR treatment
could be sold to offset the cost of the system.
The \.Vaste\.vater to be used is contributed by Silver Eagle Refinery, a petroleum refinery located in Woods
Cross. Utah. Silver Eagle Refinery, a client of Wes Tech Engineeri ng, is investigati ng the approach of
combining UASB and RABR technologies for remediation of their petroleum wastewa ter. The
vvastewater from Silver Eagle is predominantly processed by topping and catalytic reforming processes.
which consist of desalter water, sour water, and other process wastewater.
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Objectives
In order to meet State of Utah effluent guidelines, the objective of the proposed system would be an
effluent to include less than or equal to the following:
• 25 mg/L BOD*
• 25 mg/L TSS
The limits listed above are required for effluent to enter secondary receiving waters in the state of Utah
(UT Ad min Code R317-1 ). Secondar y objectives would include, but are not limited to:
• Reduction of nitrogen to at or below IO mg/L per UT Adm in CodeR309-200-5
• Reduction of phosphoru s to at or below I mg/L per UT Adm in Code R3 l 7-I
• Product ion of value-added products
Value added products such as biogas, biocrude, and protein will be observed to determi ne if the cost of
the proposed system could be offset by produced products.
*Note: as all processes tested in this design are biological processes we will assume 11COD=11BOD
Evaluation Criteria
Effluent wastewater from both UASB and RABR will be examined for COD, total nitrogen, total
phosphorus, and ammonia content according to analytica l methods. BOD and CBOD will also be
analyzed as needed. After initial trials, a formal conceptual design review will be perform ed to examine
the trajectory of the design. Optimiz ation studies will be performed on the systems, and the final system
will be chosen based on meeting the previously stated objectives.
Each criterion will be examined on a met/unmet basis where no treatment strategy will be deemed as
successful if it fails to reduce the effluent wastewater concentration to below the listed objective. If
multiple systems or designs meet listed objectives, designs will be compared through adjusted annual
operating cost analysis to find the best alternative.
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Background
Current Petroleum Waste Water Strategies
Multiple strategies are available for handling petroleum wastev,:ater.C urrently, the typical treatment
consists of two oil/water separation steps followed by biological treatment and occasionally tertiary
treatment. Prior to entering the wastewater treatment system, some refineries divert desalter effluent to an
oil/water separation step, if the current wastewater treatment system is limited, and to handle an increased
load of solids discharged during washing of the desalter. Treatment of desalter effluent results in VOC
emissions, which have to be controlled, post-oil skimming water phase, which is sent to the wastewater
treatment system, and bottom solids, which are sent to a sludge treatment plant or coker unit (IPIECA,
20 I 0). Once wastewater enters the treatment system, it takes many steps (Figure 3) to reduce excess
nutrients, heavy metals, solids, and organics to acceptable levels.
Od to 0,110
Slop S!op
Rchncr1 Primarv Secondary G1olog,ca1 Tertiary Effluent
\11/astewtae S0e1pl 1War aatt eorn S0e1p,a1rWaattieorn [ q~slizat1011 Treatment Treatrner\
Figure 3. Typical refinery wastewatert reatment diagram (IPIECA, 2010).
Separation of oil is the primary treatment for refinery wastewater. The most frequently used separator is
the API separator, which uses the difference in specific gravity separate heavier materials from lighter
liquids. Sludge is first removed from the wastewater, and as the wastewater flows through the separator,
oil rises to the top where it is skimmed off and heavy solids are scraped from the bottom. Dissolved or
emulsified oils, especially at high pH, cannot be removed by an API separator. Secondary separation of
oil and fine solids is most often done using dissolved air flotation (OAF) or induced air flotation (IAF).
DAF uses a combination of physical and chemical procedures for coagulation/flocculation to remove
dispersed pa11icles. Pait of the DAF effluent is recycled, pressurized, and then used to release air bubble
to float free oil/solids to the surface where they are skimmed off. !AF uses a rotor dispersal mechanism to
induce air into the fluid and pull oil out of suspension (IPIECA, 20 I 0).
Effluent from oil/water separation is sent to an equalization system where changes in flow are corrected,
and dampening of contaminants is provided to prevent shock loading of downstream units. Secondary
treatment is most commonly a biological treatment of either suspended growth processes or attached
growth processes. During suspended growth processes, microorganisms are suspended in the liquid where
they consume organic constituents and form biomass with the 'activated sludge process' being the most
common. Activated sludge contains aerobic biological growths in continuous suspension with wastewater
containing suspended colloidal, dissolved organic and inorganic materials. The activated sludge is
brought into contact with organic contaminants in an aeration tank where the organic material is broken
down to cell tissue, water, and oxidized products. After the aeration tank, the effluent is sent to a clarifier
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where biomass is separated into return activated sludge (RAS) or waste-activated sludge (WAS). A
sequencing batch reactor (SBR) is an alternative to activated sludge processes that is uncommon in
refinery wastewater treatment today. Membrane bioreactor (MBR) technology is also used as a variation
of activated sludge systems. Instead of clarification after the aeration tank, a membrane bioreactor is used
to separate out solids. Aerated lagoons are also a type of suspended growth process that allows for both
aeration and settling; however, they require a much larger plot area and are only used where land area is
available (IPIECA , 2010).
Attached growth processes consist of microorgani sms attached to inert packing material, such as rocks,
plastic or various synthetic materials. When wastewate r comes into contact with the material,
microorgani sms are conve1ted into more biomass and CO2. The three main attached growth processes are
trickling filters, rotating biological contactors (RBCs), and nitrification/denitrification systems. Trickling
filters consist of a bed of packing material where microorganisms form a layer, distributor s to distribute
influent over the surface of the filter and an underdrain system where the treated wastewater is removed.
A clarifier immediately follows this process to remove microbial growth that sloughs off of the filter.
RBCs consist of multiple plastic disks mounted vertically and close together. The discs are submerged
and continuou sly rotate in wastewate r to form a layer of biological mass on the discs, which causes
microorganisms to interact with the wastewater and conve1t contaminan ts to biomass and CO2.
Nitrification /denitrification processe s are used in cases where tight ammonia or nitrogen limits are
enforced. This processes essentially consists of an aeration /nitrification step, anoxic tank, and clarifier
(IPIECA , 20 I 0).
Tertia1y treatments are required if there are tight limits on TSS, COD, dissolved and suspended metals,
and trace organics. Sand filtration is often used to lower TSS in the effluent from the secondaiy treatment
clarifier. Activated carbon is one method of removing residual organics by carbon adsorption. Chemical
oxidation is not commonly used in refinery wastewater treatment but reduces COD, non-biodegradab le
compou nds, and trace organic compo unds (IPIECA, 20 I 0).
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