Advanced wastewater treatment for the fish processing industries


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Wastewater quality at the Empacadora Mar fish processing plant was evaluated and
compared with wastewater quality at other fish processing plants throughout the
world. Colloidal pollutants were found to affect process efficiency significantly. An
industrial scale Bubble Accelerated Flotation system (BAF) was installed and
operated at Empacadora Mar for three months during the summer of 2001. The
results obtained from the BAF system indicated the efficient removal of suspended
solids at a high rate. The remaining chemical oxygen demand (COD) in the
wastewater after flotation was found to originate from colloidal protein pollutants.
The problem of polluted wastewater in Ensenada is of great concern for citizens
living near the fish processing industrial park, so much so that complaints had been
filed with the city authorities about the unpleasant smell coming from the processing
plants. This project stimulated discussions between the Empacadora Mar
wastewater treatment plant operators and the research team to identify possible
strategies to eliminate, or at least reduce, the problem. Selected strategies were
studied and implemented. Details regarding the project and efforts to solve the
problem were published in a newspaper article in the El Mexicano on May 20, 2001.
New research findings were presented at the United Engineering Foundation
Conference on Flotation at Lake Tahoe, Calif., in May 2001, and a publication for a
periodical on wastewater treatment is in preparation. Two graduate students were
involved in the research effort: one student from the University of Utah and one
student from Universidad Autónoma de Baja California. The students gained
practical industrial experience during the course of the project.
The research program indicated the necessity of cooperation between city
authorities, municipal wastewater treatment plant management, and concerned fish
processing plants. Such cooperation will be useful in solving existing problems with
the smallest impact on all interested parties.ADVANCED WASTEWATER TREATMENT FOR THE FISH
In recent years, the U.S. Environmental Protection Agency (EPA) and the
Mexican Secretaría de Medio Ambiente y Recursos Naturales (SEMARNAT)
have been imposing stricter regulations on the seafood processing industry to
minimize marine pollution. Traditionally, these industries discharge wastewater
into oceans in the name of so-called nutrient enhancement. However, this
wastewater stream—contaminated with suspended solid, fats-oil-grease, and
high biological oxygen demand—has a high potential to upset the marine
ecological system. Such concerns, for example, have been discussed in local
newspapers from the state of Washington and Baja California, Mexico. The fish
processing industries in Ensenada, about 68 miles south of San Diego, are
facing similar problems from governmental authorities with respect to the quality
of the discharged wastewater. This is a clear indication of the urgent need to
develop wastewater treatment technology suitable for the fish processing
Marine pollution is an important issue in the common coastal boundary between
Mexico and the United States. The countries share a long coastal and oceanic
boundary in the Pacific Ocean, the Gulf of Mexico, and the Caribbean. A recent
National Academy of Sciences report suggested that both countries should
establish collaborative research efforts to protect the marine and ocean
environment (National Academy of Engineers 1999). Industrial wastewater is an
obvious effluent and source of pollution from all types of industries, which, if not
treated, eventually contaminates the oceans.
The fish meal industry is one industry that contributes significantly to the overall
pollution of the marine ecological system. The effluent streams from fish
processing industries contain high levels of contamination. The problem occurs
both in Mexico and in the United States. Currently, efforts are underway to
correct this situation in the United States, such as at Merinos Seafood in the2
state of Washington. Recently, significant improvements have been made in
wastewater treatment technology, and they could be implemented for the
wastewater treatment process at the Empacadora Mar fish processing works.
In this research initiative, experimental laboratory work was performed and an
industrial scale Bubble Accelerated Flotation system (BAF) was tested at the
Empacadora Mar wastewater facility. The effective use of the BAF system
depends on an understanding of the solution and colloid chemistry of the
contaminated water of interest and much effort is required for its adaptation for
the fish processing industries. Therefore, a thorough experimental campaign is
required for each application. The aim of the research included four major
• Identification and characterization of the extent of wastewater pollution
• Study of air sparged hydrocyclone (ASH) technology with respect to gas
bubble size distribution
• On-site characterization of fish processing wastewater and identification of
the source of pollutants in the process
• On-site tests of a mobile commercial scale BAF unit, preceded by
preparation of the site for installation at the Empacadora Mar fish
processing works in Ensenada
The overall benefit of this program includes the development of a technology to
reduce the level of contaminants in the effluent streams from the fish industries
and the opportunity for an important educational experience involving graduate
students from both Mexico and the United States.
BAF Flotation System
The BAF system was developed from ASH technology. Two main components of
the BAF are: a conventional ASH unit consisting of hydrocyclone header and
porous tube section for aeration of processed wastewater (Figure 1), and a
separation tank, presented in Figure 2 together with the bubble chamber (ASH
unit). Figure 3 shows the industrial BAF system.
The BAF process occurs in two steps. The first step is aeration of wastewater in
the ASH where small bubbles are sheared, collide with, and attach to solid
pollutant particles. The separation tank serves to separate bubble-solids
aggregates (aeroflocs) from the treated wastewater.
Bubble Generation and Fluid Flow
The investigation of bubble generation in the ASH was performed in previous
studies (Hupka, et al. 1994). Bubble size distribution determination was carried
out using a 2-inch internal diameter ASH unit. An aluminum cone was mounted
at the bottom of the porous tube section, as presented in Figure 4. Aerated water
was discharged on the cone surface, forming a thin layer. The wide angle of the3
cone allowed for velocity reduction of the aqueous phase. The surface of the
cone was illuminated with an electronic microflash and photos of the thin water
layer were acquired with a camera. Water velocity limited the photographing of
the smallest air bubble size. The shorter the camera shutter time and the smaller
the water velocity, the smaller the bubbles that could be photographed. Bubble
diameters were then measured from images and a sufficient number were
counted to achieve statistical significance.
Bubble size distribution from the ASH is presented as a function of methylisobutyl
carbinol (MIBC) concentration in Figure 5. In the absence of frother, a broad size
distribution of bubbles was found with a maximum number of bubbles having a
size over 1 millimeter (mm). An increase in MIBC concentration reduced the
average bubble size to around 300 microns at an MIBC dose of 32 parts per
million (ppm). The size distribution was also more narrow.
The influence of inlet water velocity and MIBC concentration on bubble size is
shown in Figure 6. In the absence of frother, and for an inlet water velocity of 1.6
meters per second (m/s), the average bubble diameter was around 3mm. When
the inlet water velocity was increased to 4m/s, the average bubble size dropped
to below 1.5mm. Addition of frother allowed for bubble size reduction. For all inlet
water velocities, an MIBC dosage of over 16ppm did not further decrease the
average bubble size.
Bubbles generated in the ASH exhibit wide size distribution. Figure 7 presents
bubble size distribution by number and volume at a sodium dodecyl sulfate
concentration of 1X10-3
M. It is evident, that the most numerous are bubbles of
sizes below 200 microns, although the most volume of air is carried by bubbles
larger than 1mm.
For comparison, Table 1 presents the bubble size range for three flotation
systems: bubble accelerated flotation, column flotation, and dissolved air flotation
(Finch and Dobby 1990; Takahashi, Miyahara and Mochizuki 1979). The BAF
system generates bubbles in a wide size range overlapping the size ranges of
the other two systems.
Fine bubbles in the ASH are generated due to three phenomena occurring in the
swirl flow inside the porous tube:
• Shear of bubbles in statu nascendi
• Coalescence of larger bubbles resulting in generation of secondary fine
• Nucleation from oversaturated aqueous phase
Shear of bubbles at the surface of the porous tube wall is the main phenomena
producing bubbles. Collisions are considered to form larger bubbles, giving rise
to a wide size distribution. The last phenomenon is considered to form the
smallest bubbles. The high pressure condition in the ASH results in dissolution of4
excessive amounts of air. Water leaving ASH decompresses and air is released
as fine bubbles.
Flow of bubbles through the separation tank is an important feature controlling
efficiency of aerofloc separation and was investigated at the University of Utah in
previous research (Desam, et al. 2001). The study determined the length of the
separation tank required for effective recovery of a bubble having a specific size.
A computational fluid dynamics (CFD) simulation was employed for
determination of optimal design and operating variables for bubble separation
from the water stream. Figure 8 presents a wire model of the separation tank with
lines representing fluid flow paths. Bubbles follow these paths, to some extent,
depending on their size. Larger bubbles detach, flow the streamlines, and are
found in separation chambers close to the inlet. Smaller bubbles need more time
to rise in the water stream and are found in the separation chambers located
farther from the inlet. Separation chambers are created by rectangular and flat
baffles placed at the top of the tank, as is visible in Figure 8. The actual
relationship between the average bubble diameter and the separation chamber
where the bubble is most likely to be found is presented in Figure 9. The
experimental measurements are compared with the simulated data, and they
agree to a large extent.
A wide distribution of bubbles generated in the bubble chamber ranging from
sizes below 50 microns to several millimeters contributes to the high efficiency
for solids removal from wastewater treated by the BAF system. Fine bubbles
attach to fine solid pollutants and are recovered in the quiescent flow regime of
the separation tank. Large bubbles remove large flocs of comparable size. The
possibility of aerating the treated wastewater with both fine and large bubbles by
the BAF bubble chamber (ASH) allows for removal of solid particles falling in a
wide size range and this excellent separation efficiency for particulate removal in
wastewater treatment.
Fish Wastewater Characteristics
Five fish body components can be distinguished (Table 2). Water accounts for up
to 71% by weight. The second most abundant constituent is the proteins. In the
case of sardines and tuna, the protein content varies between 18% and 25%.
Three main classes of proteins are: sarcoplasmic (18% to 25% of all proteins),
myofibrillar (70% to 79%), and stroma (3% to 5%). Sarcoplasmic proteins are
soluble in water or dilute salt solutions. Myofibrillar proteins are generally not
water soluble, but they dissolve at higher salt concentrations. It is worth
mentioning that salty water used at the Empacadora Mar plant facilitates
solubilization of myofibrilar proteins. Stroma proteins form connective tissues and
are not soluble in water, acid, alkaline solution, or neutral salt solutions having a
salt concentration under 0.1 mole.
Fish lipids may account for 1% to 16% of the fish weight and may be divided into
two groups. The first consists of triacylglycerols or triglycerides, and the second5
is the essential components of fish body cells, mostly phospholipids (Hall 1992;
Rollon 1999). The majority of fish lipids, around 99%, belong to the first group.
Less than 1% are phospholipids.
Carbohydrates are present only in some species and account for less than 4% of
the fish weight. They are stored in the liver as glycogen. This polysaccharide is
built from glucose units and is transported from the liver to muscle as an energy
source when needed. Mineral compounds in the case of sardines and tuna
compose less than 3% of the fish weight.
Table 2 presents the composition of sardines and tuna, the fish used at the
Empacadora Mar plant for canning.
Examples of fish processing wastewater from Argentina, Algeria, and Spain are
presented in Table 3, and the characteristics of the wastewater from the
Empacadora Mar plant is shown in Table 4. The most important wastewater
characteristics include pH, chemical oxygen demand (COD) and biological
oxygen demand (BOD). COD is the amount of oxygen required for oxidation of
organic matter by chemical methods (Nollet 2000). Biological oxygen demand is
the amount of oxygen needed for oxidation of organic matter by biological action
under specific standard conditions. When discussing the impact of industrial
wastewater on the environment, pH and COD (or BOD) are the main factors
determining the severity of the problem. High deviations of wastewater pH from
neutral are capable of terminating aquatic life at the place of wastewater
discharge. Excessive organic matter contained in wastewater does not help
aquatic life, but leads to eutrophisation. In the case of food processing
wastewater, COD and BOD are closely correlated and BOD levels are around
60% of those measured by COD methods. The COD determination is less time
consuming, more simple, and more reproducible compared to that of BOD.
The wastewaters considered in Table 3 exhibit neutral or close to neutral pH,
ranging from pH 6.3 to pH 8.0. Wastewater samples significantly varied in the
content of pollutants. COD was between 549 milligrams per liter (mg/L) and
93,000mg/L. Total suspended solids reached a level of almost 30 grams per liter
(g/L), as found in fish meal wastewater from Spain. The distribution of pollutants
between lipids, proteins and carbohydrates was determined only in the case of
the tuna cooking plant in Spain. It was found that as much as 77% of COD
originated from proteins.
The COD in wastewater from Empacadora Mar can reach extremely high levels,
even 400,000mg/L COD, as presented in Table 4. This exceptionally high level is
not common however, and average wastewater COD ranges from around
10,000mg/L to 80,000mg/L. Typical COD values at Empacadora Mar do not
exceed 80,000mg/L as is found in other fish processing plants throughout the
world. The suspended solids in wastewater from the Empacadora Mar plant were
also at the highest level when compared to the results for wastewater from plants6
presented in Table 3. The highest detected total suspended solids (TSS) content
was 30.8g/L, see Table 4. Wastewater generated at Empacadora Mar originates
from several plant processes. Main wastewater streams come from thawing,
gutting, steam cooking, pepper roasting, and floor cleaning operations.
Fish wastewater from the Empacadora Mar plant was investigated for the
distribution of pollutants between suspended solids, dispersed colloids, and
dissolved substances. Table 5 shows the ************ysis of wastewater before
processing and after filtration through Whatman 50 filterpaper. The test results
show that approximately 70% to 80% of the pollutants originated from suspended
solids, which were retained on the filter paper. The remaining organic matter was
either dissolved or dispersed in colloidal form.
The obtained filtrate was further investigated to determine the size of the colloidal
particles. Figures 10 and 11 present the size of colloidal particles as a function of
pH and time of conditioning respectively. Effective particle size was determined
using Brookhaven size ************yzer ZetaPals. No significant dependence of colloidal
particles size on pH and time of conditioning could be found.
A comparison of the filtered wastewater and wastewater treated with cationic
polymer C-498-HMW (manufactured by Cytech) at a dose of 50ppm, was made
(Table 6). This very high molecular weight polyacrylamide has a charge density
of 60%. The average colloid size of an untreated sample was 734 nanometers
(nm), while the treated sample contained aggregates of more than 2 microns in
size. This indicates that although an increase of colloidal particle size occurs, it is
not sufficient for its efficient removal.
The significant problem encountered during the course of this investigation was
that very little of the colloidal protein pollutants could be removed by the
polymeric flocculant BAF treatment.
Jar Testing
Jar testing is a well-established laboratory method to evaluate the extent to which
suspended particles can be removed from wastewater by flocculation (Industrial
Waste Treatment). Preliminary jar tests of Empacadora Mar wastewater
indicated efficient solids removal and the possibility for COD reduction to the
level of 7,000mg/L to 15,000mg/L (Tables 7 and 8). Ferric chloride was used in
the amount necessary to lower the pH to the desired value and polymers were
used at a level of 20ppm to 30ppm. Both methods of water treatment reduced
suspended solids significantly. Turbidity decreased from very high values of more
than 1,000 nephelometric turbidity units (ntu) to values around 20ntu. The
performance of polymeric flocculants was slightly better than ferric chloride
(FeCl3) when considering COD reduction. Tests of supernatants after treatment
indicated good solid removal and COD reduction to 7,000mg/L to 15,000mg/L7
from initial values between 30,000mg/L and 80,000mg/L. Worth mentioning is
that both methods allowed for COD reduction originating from suspended solids,
however soluble and colloidal pollutants remained in the supernatants. COD
values of treated samples are close to those of filtered raw wastewater samples.
Selected results of jar tests are presented in Tables 7 and 8. The sample
presented in Table 7 was taken in September 2001 (treatment with FeCl3 and
double polymer flocculation, polymers: cationic C-498-HMW and the high
molecular weight anionic polymer used by Empacadora Mar for dissolved air
flotation (DAF) details were not disclosed). The sample presented in Table 8 was
taken in September 2001 (treatment with FeCl3 and cationic polymer C-498-
It is clear that an appropriate treatment of the wastewater with recently
developed very high molecular weight cationic and anionic polymers is capable
of removing organic pollutants with slightly better efficiency when compared to
FeCl3 treatment. Solids were easily removed using applied inorganic coagulants
or polymers, however the finest colloidal and soluble pollutants remained in the
wastewater, as shown by comparison with the filtered wastewater sample.
Plant Testing of BAF System
The BAF system was successfully installed at the Empacadora Mar plant during
the last week of June 2001 and was operated for more than two months. The
installed BAF was equipped with a 6” ASH and is capable of processing from 80
gallons per minute (GPM) to 250GPM, however the typical flowrate used during
tests ranged from 100GPM to 110GPM. The dimensions of the BAF unit are 4
feet wide, 12 feet long and 8 feet high. Figures 12 through 19 are photographs of
the installation and operation of the BAF at Empacadora Mar.
Figures 20 and 21 present plant results with the BAF system for 12 consecutive
working days. Figure 20 shows suspended solids content before and after
treatment. The highest solids content in the wastewater before treatment
measured during this period was more than 15g/L. A very low content of solids
remained after treatment. Figure 21 shows the COD content of untreated and
treated wastewater. The efficiency of COD removal was the best when solids
content was high. In two cases, when suspended solids were very low, below
1g/L in days 2 and 8, the efficiency of COD removal was extremely poor.
As mentioned above, wastewater at Empacadora Mar originates from various
processes, like thawing, pepper roasting, gutting, steam cooking, and floor
cleaning. The wastewater directed to the plant treatment is a mixture of
wastewater from these operations in proportions that are not strictly defined. For
this reason, the COD in the treated wastewater appears independent from the
COD and suspended solids content in the feed wastewater, as can be concluded
from the graphs in Figures 20 and 21.8
Additional examples of BAF operation from two selected days are provided in
Tables 9 and 10. These results present additional data for pH and turbidity
measurements as well as calculations of COD and TSS reduction levels.
Wastewater from Run A was conditioned with FeCl3 in an amount to lower the pH
to the desired value. The wastewater was then conditioned with an anionic
polymeric flocculant at a dose of 30ppm and fed to the BAF at a flowrate of
The results for Run B were obtained using FeCl3 in amount necessary to lower
the pH from 6.9 to 6.1. Following pH adjustment, the wastewater was fed to the
BAF at a flowrate of 100GPM conditioned with cationic flocculant C-498-HMW in
the amount of 54ppm. In addition, in Table 10, COD ************ysis of filtered
wastewater was included to further evaluate BAF performance.
In these BAF tests it was possible to obtain a COD reduction of more 37% for
Run A and 79% for Run B. The lowest COD for BAF effluent was 5,120mg/L.
Both tests had very high solids reduction, from 96% to more than 99%. Untreated
wastewater from Run B was filtered to remove suspended solids and ************yzed
for COD. On this basis, it was revealed that the efficiency achieved with the BAF
was limited by the presence of soluble and colloidal pollutants of sizes below 1
micron. The COD from the BAF effluent was only slightly lower than that of
filtered untreated wastewater. This observation is similar to the observation made
during jar testing, under which circumstances the COD of the supernatant was
comparable to the COD of the filtered sample. These results indicate that the
BAF system is efficient for the removal of suspended solids but the removal of
soluble and colloidal substances of size below 1 micron requires further research
During this research program on the evaluation of BAF technology at the
Empacadora Mar fish processing plant the following conclusions have been
• Empacadora Mar fish processing wastewater exhibits one of the highest
levels of contamination documented for this kind of processing plant. Of the
two most polluting streams—tuna canning and fish meal production—the
second adds a high level of contamination with the COD ranging from
80,000mg/L to 40,000mg/L. Typically this water is mixed with other plant
• The BAF system turned out to be efficient in suspended solids removal,
which typically exceeded 99%. The efficiency of COD reduction reached
79%. Soluble and colloidal pollutants of a size below 1 micron were difficult
to remove with the BAF system. However, colloid particle size ************ysis
showed that cationic polymer flocculation increased the size from 734nm to
2,174nm. Further study of colloid flocculation and separation is suggested.
The amount of colloidal and dissolved substances still accounts for
6000mg/L to 8000mg/L of the COD level after BAF treatment.9
• It was confirmed that polymers can replace inorganic coagulants yielding the
same COD reduction efficiency, which is important when the separated
solids are used as an additive to fish meal. Inorganic salts of metals like iron
or aluminum render recovered solids unusable for production of animal
• The BAF system was valued by Empacadora Mar employees for the highly
specific capacity of wastewater processing, which allowed for additional
space to become available at the water treatment plant. The BAF system
replaced the existing traditional DAF operation, which was 100 times larger
in size
The following recommendations for Empacadora Mar wastewater treatment
operations are made:
• Fish meal wastes can be treated in the BAF system, dynamically responds
to the high COD load increase caused by this kind of wastewater.
• The BAF system for removal of solids should be permanently installed. The
BAF system is capable of processing in a relatively short time of four hours
all the wastewater generated at the Empacadora Mar plant during the day.
This will ensure better control over the wastewater treatment process.
Additionally, due to the small size of the BAF, significantly more space will
become available at the water treatment plant.
• Homogenizing feed wastewater in a stirred cylindrical tank placed above
ground level with the outlet placed underneath the tank is recommended
prior to flotation. Appropriate mixing of wastewater will assure the most
economical flotation process. Changes in feed properties cause
deterioration of effluent quality. Use of underground sumps is not
recommended because of the difficulty of cleaning them and the difficulty in
control and management of the circuit.
• Further research on the removal of COD originating from colloidal and
soluble pollutants is recommended. A COD content of more than 5,000mg/L
is typical at Empacadora Mar due to the colloidal and soluble contaminants.
This level is still significantly higher than the discharge limit of 1,000mg/L
imposed by the Ensenada city authorities.
The BAF system was found to be efficient for the removal of suspended solids.
Because of the highly specific capacity of the BAF, wastewater treatment from a
whole day of operation could be accomplished during a short time of only four
hours. Valuable practical experience was gained by both Empacadora Mar
employees and the research team during the course of this project. A meeting of
city authorities, municipal wastewater treatment management officials, and fish
processing industry park employees was held to discuss the need for and
possible benefits of cooperation in solving existing problems. As a result of this
research program, the contamination problem was defined in greater detail and
new research objectives were identified.10
The authors would like to acknowledge help from Empacadora Mar management
and employees, and recognize the significant contributions of time, effort,
equipment, and installation/operation from Clean Water Technologies during the
course of this research program. Financial support from Southwest Center for
Environmental Research and Policy (SCERP), Project No: W00-3, made this
research program possible.
Anonymous. 1999. News Report from the National Academy of Engineers,
Civit, E. M., M. A. Parin, and H. M. Lupin. 1982. “Recovery of Protein and Oil
from Fishery Bloodwater Waste.” Water Research 16:809.
Desam, P. R., A. Datta, W. Morse, and J. D. Miller. 2001. “A Computational Fluid
Dynamics (CFD) Model for a Bubble Separation Tank Used in Wastewater
Treatment.” To be published in Proceedings of the United Engineering
Foundation Conference: Froth Flotation/Dissolved Air Flotation.
Finch, J. A., and G. S. Dobby. 1990. Column Flotation. Elmsford, New York:
Pergamon Press.
Genovese, C. V., and J.F. Gonzalez. 1982. “Evaluation of Dissolved Air Flotation
Applied to Fish Filleting Wastewater.” Bioresource Technology 50:175-179.
Guerrero, L., F. Omil, R. Mendez, and J. M. Lema. 1998. “Protein Recovery
During the Overall Treatment of Wastewaters from Fish-Meal Factories.”
Bioresource Technology 63:221-229.
Hall, G. M., ed. 1992. Fish Processing Technology. Glasgow, New York: Blackie
Academic & Professional.
Hupka, J., R. P. Bokotko., D. Lelinski, and J. D. Miller. 1994. Proceedings of the
International Coal Preparation Congress. Wieslaw Blaschke, ed. The
Netherlands: Gordon and Breach Publishers.
Mameri, N., D. Abdessemed, D. Belhocine, H. J. Lounici, C. Gavach, J.
Sandeaux, and R. Sandeaux. 1996. “Treatment of Fishery Washing Water by
Ultrafiltration.” Journal of Chemichal Technology and Biotechnology 67(2):169-
Mendez, R., F. Omil, M. Soto, and J. M. Lema. 1992. “Pilot Plant Studies on the
Anaerobic Treatment on Different Wastewaters from a Fish-canning Factory.”
Water Science and Technology 25(1):37-44.11
Nollet, L. M. L., ed. 2000. Handbook of Water ************ysis. New York and Basel,
Switzerland: Marcel Dekker, Inc.
Rollon A. P. 1999. “Anaerobic Digestion of Fish Processing Wastewater with
Special Emphasis on Hydrolysis of Suspended Solids.” PhD. dissertation,
Wageningen Agricultural University, Wageningen, Netherlands. A.A.Balkema,
Takahashi, T., T. Miyahara, and H. Mochizuki. 1979. “Fundamental Study of
Bubble Formation in Dissolved Air Pressure Flotation.” Journal of Chemical
Engineering of Japan 12(4):275-280.
U.S. Environmental Protection Agency, Office of Water Programs. 1996.
Industrial Waste Treatment. Volume 1, Chapter 8.Figure 4. Experimental Setup for Bubble Size Determination0.2
32 ppm
16 ppm
8 ppm
4 ppm
0 ppm 0
by Number
Bubble Size
Figure 5. Number Size Distribution of Bubbles from a 5 cm ASH as a Function of MIBC
Concentration for Qwater = 75 L/min and Qair = 90 L/min
Figure 6. Size Distribution of Bubbles from the ASH as a Function of MIBC Concentration for
Various Feed Inlet VelocitiesFigure 8. Streamlines for Fluid Flow in the Separation Tank (Desam et al. 2001)
Figure 9. Bubble Size Distribution for Experiments and Simulations (Desam et al. 2001)
Figure 7. Bubble Size Distribution from ASH, 1 10-3 ppm SDSFigure 10. Particle Size of Colloids as a Function of pH. Conditioning Time 1 Minute
Figure 11. Particle Size of Colloids as a Function of Conditioning TimeFigure 12. Installation of BAF at Empacadora Mar, Ensenada, Mexico. Positioning at Plant
Location, June 2001Figure 13. Installation of BAF at Empacadora Mar, Ensenada, Mexico. Plumbing and
Connection of Pipelines, June 2001Figure 14. BAF after Installation at Empacadora Mar, Ensenada, Mexico. View from the Bubble
Chamber (ASH) Side, September 2001Figure 15. BAF after Installation at Empacadora Mar, Ensenada, Mexico. View From Solids and
Effluent Discharge Side, September 2001Figure 16. BAF during Operation at Empacadora Mar, Ensenada, Mexico, September 2001Figure 17. Top of BAF Separation Tank at Empacadora Mar, Ensenada, Mexico. Floated Solids
Firmly Retained at the Water Surface. September 2001Figure 18. Floated Solids Discharge from BAF at Empacadora Mar, Ensenada, Mexico,
September 2001Figure 19. Effluent Discharge from BAF at Empacadora Mar, Ensenada, Mexico, September
2001Figure 20. BAF Treatment. Suspended Solids Removal
Figure 21. BAF Treatment. COD ResultsTable 1. Bubble Size Comparison
Flotation System Bubble Size Range
ASH (BAF) 50 ñ 3,500
Column Flotation 650 ñ 1,500
DAF 30 - 180
Table 2. Composition of Sardines and Tuna Fish (wt. percent)
Fish Water Proteins Lipids Carbohydrates Ash
Sardines 65 ñ 71 18 - 20 4 ñ 16 0 3
Tuna 67 ñ 71 23 - 25 1 ñ 7 0 - 4 1.2 ñ 1.7
Table 3. Fish Wastewater Characteristics
Wastewater, Country, Ref.
Lipids Proteins Carbohydrates
Fish filleting, Argentina,
(Genovese and Gonzalez
8.0 549 - 3.2 - 0.044 g/L -
Fish processing, Argentina,
(Civit, Parin and Lupin
6.9 93,000 - 7.3 0.12 g/L - -
Fishery Washing, Algeria,
(Nameri et al. 1996)
7.0 9,300 3.0 15 - 5 g/L
Tuna cooking, Spain,
(Mendez et al. 1992)
- 34,500 - 4.0 12 % COD
77 % COD 11% COD
Fish Meal from tuna bones,
Spain, (Guerrero et al. 1997)
6.4 46,700 13.0 - - - -
Fish Meal from tuna heads,
Spain, (Guerrero et al. 1997)
6.3 81,300 29.9 - - - -
Fish Meal from sardine
heads, (Guerrero et al. 1997)
6.5 38,200 6.6 - - - -Table 4. Empacadora Mar Fish Wastewater Characteristics
Wastewater, Country, Ref. pH COD TSS
Tuna and Sardines Processing, Empacadora Mar, Mexico,
2000, CWT laboratory report
6.0 81,200 mg/L 30.8 g/L
Pepper Water, Empacadora Mar, Mexico, 2001, CWT
laboratory report
5.7 12,180 mg/L 2.1 g/L
Fish Meal, Empacadora Mar, Mexico, 2001, Factory Lab. - 80,000 - 400,000 mg/L -
Tuna and Sardines Processing, Empacadora Mar, Mexico,
2001, this work
6.9 40,000 mg/L 10.5 g/L
Table 5. Distribution of Pollutants. Wastewater Filtered by Whatman 50 Filterpaper
TSS in raw
(g/L) Before Filtration After Filtration
Remaining COD
I 10.5 40,000 8,800 22
II 30,000 8,200 27
III 80,000 >15,000 >19
Table 6. Particles Size of Colloids after Treatment with Cationic Polymer (C-498-HMW, Cytech,
Dose: 50 ppm)
Wastewater Effective Diameter
Standard Error
Untreated 734 33.6
Treated with cationic polymer, C-498-HMW 2174 47.3
Table 7. Jar Testing of the Empacadora Mar Wastewater
Wastewater sample pH Conductivity
Untreated wastewater 6.8 29.0 >1000 30,000
Wastewater after filtration - - 27 8,200
3 coagulation, followed by lime treatment 9.0 - 19 8,400
Double polymer treatment - - 25 7,000Table 8. Jar Testing of the Empacadora Mar Wastewater
Wastewater sample pH Conductivity
Untreated wastewater 7.2 30.5 >1000 80,000
Wastewater after filtration - 27.0 22 >15,000
3 coagulation, 1000mg/L 5.6 30.8 148 >15,000
Polymer treatment, cationic C-498-HMW 9.0 - 36 13,500
Table 9. Treatment of Wastewater by BAF at Empacadora Mar, Run A. September 5, 2001
Sample pH COD
COD Reduction
TSS Reduction
Untreated wastewater 6.7 8,200 - 3.40 - >1000
Effluent I 6.0 5,120 37.6 0.13 96.2 66.4
Effluent II 5.7 5,560 32.2 0.02 99.2 26.0
Table 10. Treatment of Wastewater by BAF at Empacadora Mar, Run B. September 5, 2001
Sample pH COD
COD Reduction
TSS Reduction
Untreated wastewater 6.9 40,000 - 10.45 - >1000
Effluent III 6.1 8,400 79.0 0.15 98.6 87.1
Filtered wastewater 6.9 8,800 78.0 - - -
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