ENVIRONMENTAL PROTECTION ACENCY
OFFICE OF ENFORCEMENT
EPA-330/2-78-004
E n g i n eer i n g Ei a I u at io n
Water and Air Compliance
Honokaa Sugar Company
Honokaa, Hawaii Sugar Cane Mill
NATIONAL ENFORCEMENT INVESTIGATIONS CENTER
DENVER, COLORADO
AND
REGION IX. SAN FRANCISCO
MARCH 1978
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Environmental Protection Agency
Office of Enforcement
EPA-330/2-78-004
ENGINEERING EVALUATION
WATER AND AIR COMPLIANCE
HONOKAA SUGAR COMPANY
HONOKAA, HAWAII SUGAR CANE MILL
March 1978
National Enforcement Investigations Center - Denver
and
Region IX - San Francisco
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TABLE OF CONTENTS
I. INTRODUCTION 1
II. SUMMARY AND CONCLUSIONS 3
III. PROCESS OPERATIONS 8
IV. DERIVATION OF RAW WASTE LOADS FOR
HONOKAA SUGAR COMPANY 10
V. AIR AND WASTEWATER POLLUTION CONTROL 16
AIR POLLUTION 16
WASTEWATER 17
VI. UNAUTHORIZED DISCHARGE FROM BOILING HOUSE
AND BOILING HOUSE RESERVOIR 26
VII. NPDES REQUIREMENTS, SELF-MONITORING, SAMPLING
AND FLOW MEASUREMENT 27
NPDES PERMIT LIMITATIONS 27
NPDES SELF-MONITORING RESULTS 28
SAMPLING AND FLOW MEASUREMENT AT THE
HONOKAA 001 MONITORING STATION 28
ADDITIONAL SAMPLING LOCATIONS AT HONOKAA WWTP . . 31
VIII. ANALYSIS OF HONOKAA WWTP DESIGN 33
IX. SUPPLEMENTAL REFERENCES ON TREATMENT DESIGN ... 39
TABLES
I Solids and BOD Loads in Final Discharge
Prior to July 1977 29
II Solids and BOD Loads in Final Discharge
July to December 1977 30
FIGURES
1 Water Balance, Honokaa Sugar Co 18
2 Honokaa Sugar Co., Water Treatment System .... 19
3 Suggested Sampling, WWTP Influent 32
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I. INTRODUCTION
The Honokaa Sugar Company cane factory is located approximately 40
miles north of Hilo, Hawaii, on the Hilo-Hamakua Coast of the Big Island
of Hawaii. In August 1977, EPA Region IX requested assistance of NEIC-
Denver in support of an enforcement action against the Honokaa Sugar
Company. The Company stated on June 27, 1977 that during periods of
prolonged wet weather, the treatment system was underdesigned but addi-
tional equipment has been ordered which should be operational in March
1978. Honokaa Sugar Company was scheduled to comply with NPDES final
limitations on July 1, 1976. The Discharge Monitoring Reports submitted
by the Company show Total Suspended Solids (TSS) excesses for'the months
of October and November, 1976 and March through May, 1977. Settleable
solids limits have been violated continuously during the months of July
through November 1976 and March through June 1977.
NEIC-Denver met with the Region IX Enforcement Division staff on
September 23, 1977, in San Francisco including Messrs. Harlan Agnew,
Robert Wills, Greg Fischer and Terry Brubaker. NEIC was asked to investi-
gate the Honokaa Sugar Company situation with special emphasis upon: 1)
corroborative evidence on the nature of documented air and water viola-
tions; 2) thorough evaluation of the Honokaa treatment systems, current
operation and maintenance practices, and conditions corresponding to
design treatment criteria; and 3) determine if possible, additional
equipment necessary to achieve compliance and the time required for
installation.
The Honokaa field evaluation was made by Mr. E. J. Struzeski over
the period of October 24 through October 31, 1977. Field support was
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provided by Mr. Greg Fischer during October 24-27 and Mr. William Sonnet
of the Effluent Guidelines Division, EPA Headquarters over October 24-
28.
EPA met with the Honokaa Sugar Company in Hawaii on October 24, 27
and 29, 1977. Contacts were also made at other times. Information con-
tained in this report was obtained from EPA Region IX files, Honokaa
Sugar Company officials, and supplemental data sources including the
Dorr Oliver Company of Stamford, Connecticut, published papers, etc.
In-depth discussions were held with Honokaa Sugar Company including Mr.
P. Ernest Bouvet, Vice President and General Manager; Mr. Jean-Paul
Merle, Boiling House Superintendent; and Mr. John Bersch, Technical
Director, Sugar Engineering and Special Consultant with Theo H. Davies
and Company, Ltd., Honolulu. Laupahoehoe Sugar Co. personnel attended a
meeting on October 27, 1977, held at the Honokaa facilities which included
Mr. Gordon Trenholme, Environmental Coordinator and Mr. Tim Bennett,
Associate Engineer from Laupahoehoe Sugar.
In February 1975, NEIC-Denver together with Region IX and the State
of Hawaii conducted a reconnaissance inspection of the Honokaa Sugar
Company. This was followed by a compliance monitoring survey in May
1975 and a report giving an evaluation of the 1975 findings.* The
October 1977 activity represents an extension of the earlier inves-
tigation.
* "Report on Compliance Monitoring at the Honokaa Sugar Company,
Honokaa3 Hawaii, Hawaiis " EPA} National Field Investigations Center,
Denver, Colorado} September 43 1975.
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II. SUMMARY AND CONCLUSIONS
1. Estimates of soil loads entering the Honokaa WWTP were developed in
1973 by Mr. John Bersch of Theo Davies and Company, Ltd. These values
were used by Region IX in developing the NPDES permit. It now appears
that soil loadings in the Bersch analysis were expressed as WET rather
than DRY weights as had been originally believed. The Bersch analysis
also assumed substantial implementation of Toft harvesters which would
give a cleaner cane coming into the Honokaa factory. (However, the
concept of Toft harvesting appears now to have been minimized by the
Company). Consequently, the Honokaa WWTP was likely designed on the basis
of around 250 TPD dry solids. Wet weather loads have since been shown
to reach up to 600 TPD dry solids. Mr. Jean-Paul Merle of Honokaa Sugar
in a November 1976 paper stated that solids loads as high as 544 TPD dry .
solids are entering the hydro-separator compared to the 250 TPD dry
solids that had been predicted in 1973-1974. Based upon these factors,
the Honokaa WWTP is significantly underdesigned.
2. The John Bersch analysis and the NPDES permit for Honokaa were
developed on the basis that 33 to 50% of all cane would be harvested by
Toft means. Minimizing the Toft concept has placed a greater waste load
upon the Honokaa WWTP. The Company did not inform the EPA and the State
of the consequences of this change. Further, no provisions were made to
compensate for waste load increases caused by non-implementation of the
Toft harvesting. Honokaa Sugar continues to utilize 100 percent push-
rake harvesting which transfers maximum soil loads from the field to the
factory.
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3. When the full-scale Honokaa WWTP was started up in August 1975,*
pretreatment consisting of DSM screens was incorporated as an essential
part of the overall system. The DSM screens were intended to remove up
to 60 percent of the incoming TSS and offer suitable protection to the
hydroseparator and vacuum filter. The DSM screens were abandoned in
early 1976 because of excessive wear. A grit separator was subsequently
installed and is said to remove up to 6 percent of the TSS. It is
evident that the grit separator is not an adequate substitute for the
DSM units and the hydroseparator and vacuum filter are experiencing
greatly increased loads over previous levels. Compensations have not
been made for these increases.
4. The Honokaa WWTP was designed for a wastewater flow of 4.5 mgd.**
Based upon Company results over the period of July 14, 1976 to November
30, 1976, flows in the Honokaa WWTP circuit have exceeded the 4.5 mgd
design on 22 of the 39 days of record. These flows are detrimental to
WWTP removal efficiencies.
5. Design of the full-scale hydroseparator was based upon laboratory
experiments without benefit of pilot plant study. Conservative engineer-
ing design should be used when extrapolating from laboratory settlea-
bility tests to full-scale clarifiers. This may not have been the case
at Honokaa. Wastewater detention time and water depth are minimal with
the Honokaa hydroseparator and are less than conventional treatment
design. The hydroseparator is relatively shallow and does not permit
good separation of the sludge blanket from the quiescent settling zone.
* However it was not until June 1976 that the vacuum filter necessary
for dewatering solids removed by the hydroseparator was actually
installed. WWTP sludges were discharged to the final effluent.
** From "Laboratory and Pilot Plant Study of Factory Wastewater, " Jean-
Paul Merle} paper presented at 33rd Annual Conference of Hawaiian
Sugar Technologistss November 1974, and Report of NEIC trip made to
Dorr-Oliver} Inc., Stamford3 Conn.3 October 113 1977,
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There is also limited opportunity for retaining and consolidating the
bottom sludges. Mr. Richard Hunwick of Dorr Oliver in a 1977 published
paper* has described the Honokaa-type low detention system as ...
"becoming more tempermental, i.e. less resistant to shock loads, and ...
(requiring) ... careful monitoring of the operation."
6. During the week of October 23, 1977, the hydroseparator overflow
was observed to be heavily laden with solids; large quantities of
floatable material and fly ash were present on the surface of the clari-
fier; and excessive flow surging was occurring at the center well of the
clarifier. Dorr Oliver has indicated that fly ash adversely affects
solids separation in the settler. High flow velocities at the center
well reduce separation capabilities. The Honokaa treatment system also
lacks waste equalization which decreases solids removal efficiency.
7. Sizing of the vacuum filter at Honokaa was probably based upon a
WWTP design load of 250 TPD dry solids. When the Company realized that
incoming solids loads could peak as high as 600 TPD dry weight, a second
vacuum filter was ordered from Dorr Oliver, Inc. This second unit is
expected to be installed in Spring 1978. Mr. Jean-Paul Merle of Honokaa
Sugar Co. has stated that filtration rates with the stainless steel
filter media are in the range of 40 to 50 lb dry solids/ft^/ hour. Two
10 foot by 20 foot rotary vacuum filters may not be adequate to cope
with maximum soil loads, especially if Honokaa decides to increase its
process rates.
8. An unreported discharge was found during the week of October 23,
1977, originating as an overflow from the Honokaa boiling house reservoir
and finding its way to the ocean. Other waste releases from the main
boiling house may also be occurring.
* "Treatment of Sugar Cane Wash Water," Hunuicks E.J., Sugar y Azucar,
pp 73-80j March 1977.
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9. Self-monitoring results for 1976 and 1977 were reviewed and com-
pared to NPDES permit limitations. Final limitations came into effect
on July 1, 1976. Since July 1976, the Company has been in violation of
the average daily TSS limits in 8 of 12 months for which data are avail-
able through September 1977. On settleable solids limits, the Company
has been out of compliance for virtually the entire period from July
1976 to September 1977. A definite correlation exists between TSS and
settleable solids in the Honokaa 001 effluent. For the four months in
which the permittee was in compliance with TSS limits, settleable solids
averaged about 3 ml/1. During the remaining months when the permittee
was out of compliance, the settleable solids averaged 26 ml/1. The
Company in June 1974 proposed effluent limits of 1.0 mg/1 on an average
daily basis and 2.0 ml/1 on a maximum daily basis. Based upon Laupahoehoe
Sugar Co. experience in meeting permitted TSS limits and corresponding
settleable solids levels, the latter parameter for Honokaa could be
reestablished as 2.0 ml/1 on an average daily basis and 5.0 mg/1 on a
maximum daily basis.
10. Not only has Honokaa violated NPDES permit limits almost continu-
ously since July 1976, but also there has been no improvement in effluent
quality over this same period. Discharge volume has changed in the past
few months because part of the effluent is now being diverted to field
irrigation. Based upon the record, the Honokaa WWTP will not meet the
permitted limits the majority of the time. Permit violations will occur
predominately during the wet months of February through April and October
through December, but will also occur through the drier months of May
through September, at least part of the time. It is doubtful that the
Honokaa WWTP could meet NPDES limits a high percent of the time given
the lack of substantial "pretreatment" (such as DSM screens) even if
another vacuum filter and clarifier were added to the system. A partial
solution may be to construct solids bleedoff ponds similar to that of
the Laupahoehoe Sugar Company. However, even this measure may not
assure consistent attainment of permit levels.
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11. A new boiler system which is under construction at Honokaa is
expected to be completed in late 1978. The Company hopes that the new
boiler and its attendant controls will overcome air pollution and
emission violations that have persisted over the years. However, there
is no strong guarantee that this will occur. As best as can be deter-
mined,' the new boiler will allow Honokaa Sugar to expand processing to
the 200 TPH net cane level. Effects of a process increase could adversely
impact upon wastewater treatment. No wastewater treatment plans have
been announced to cope with possible increase in sugar cane processing
rates as indicated by the new boiler construction.
12. Visible emissions (air) tests were conducted by NEIC-Denver on
October 29, 1977, and again on October 31, 1977. The results of three
tests were in excess of the Hawaii SIP.
13. BOD (although not a permitted parameter) continues at high levels
in the Honokaa wastewater discharge in spite of treatment. The Hilo-
Hamakua Coast factories have shown that BOD loads will remain almost
constant regardless of the level of TSS removal. BOD could be of major
concern in the future.
14. Honokaa Sugar is presently conducting sampling of the WWTP influent
and effluent under agreement with the Hawaii State Department of Health
order dated January 14, 1977 (Docket No. PIE-E0-W-40). The Company
conducts analysis on a composite sample made up of 20 individual grab
samples taken over a seven consecutive day period. Honokaa Sugar then
applies the single composite sample result to the daily flows to give
seven different daily waste load values. The manner and duration over
which the samples are composited and the type of calculations made by
the Company cause these data to have limited value. This sampling
program should be modified to provide more meaningful data on WWTP
removal efficiencies.
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III. PROCESS OPERATIONS
The Honokaa Sugar Company exclusively relies upon the pushrake
method of field harvesting because of relatively steep and rocky terrain
over the plantation. Pushrake harvesting is the least expensive means
of moving the cane from the field to the factory but also produces
the maximum amounts of trash and soil carried with the cane to the
factory. Honokaa receives 60 to 70 inches of rainfall annually com-
pared to 110 inches per year by the adjoining Laupahoehoe Sugar Company.
Irrigation is practiced by Honokaa Sugar about 6 months of the year.
The process campaign at Honokaa Sugar normally extends from around
early March through late November. Over the first half of 1977, monthly
average receipts of net cane have ranged between 2,600 and 3,000 TPD.
Corresponding field cane receipts have been 4,700 to 5,300 TPD. The
mill operates 24 hours per day, 7 days per week. Scheduled plant main-
tenance is conducted generally on Tuesdays from 0700 to 1500 hours at
which time processing is stopped.
Cane cleaning at Honokaa consists of three stages of cane washing
and cleaning. After cleaning, the cane is sliced, shredded and passed
through a series of 5-roll press mills. Four milling stages are present.
Bagasse, juice and molasses represent the main products from the milling
operations.
Honokaa Sugar generates steam and electricity by hydro and by
conventional means. Water from the upper part of the plantation reaches
the mill site carrying a pressure head of 200 psi. Bagasse represents
the primary fuel at the Honokaa factory. The Honokaa boiler produces up
to 160,000 lb/hour steam at 550 to 610 psi. Moisture content of incoming
bagasse is usually maintained between 44 and 52 percent.
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The Honokaa boiler system was purchased second-hand in 1963 and
converted from a coal-burning to a bagasse-burning unit. Company per-
sonnel in October 1977 and also in an application of variance on June 3,
1977 affirmed that stack emissions continue to exceed permissable limits,
especially in bad weather. Installation of a scrubber system probably
could bring the existing boiler into compliance. However, the Honokaa
Sugar Company indicated that space was unavailable for this equipment.
A new boiler is under construction.
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IV. DERIVATION OF RAW WASTE LOADS FOR HONOKAA SUGAR COMPANY
Soil loads coming into the Honokaa sugar mill were essentially
based upon study results developed by the Hawaiian Sugar Planters Asso-
ciation (HSPA) in 1969. These results were subsequently refined by Mr.
John Bersch of Theo Davis & Co. in 1973. The HSPA focused upon an
experimental dry cane cleaner system at Laupahoehoe, and in this study,
soil load estimates were developed for both wet and dry weather condi-
tions. The HSPA report made available in October 1969 was titled
"Experiment Station, Hawaiian Sugar Planters Association, Technical
Supplement to Factory Report 58 and Mechanization Research Report 12,
Cane Dry Cleaning at Laupahoehoe Sugar Co., 1969" compiled by Warren
Gibson and L. J. Rhodes. A summary of Mr. John Bersch's analysis is
presented below. Most importantly, soil and trash loadings in the
Bersch analysis very much appear to be expressed in terms of WET weights
rather than DRY weights. These same data given to the EPA in 1973-1974
were asssumed to have been dry weight values. This has created confusion
in constructing the technical history on waste treatment at Honokaa.
A) THEO DAVIES ANALYSIS
Yearly crop estimated at 675,000 net tons 2700 TPD net cane
assuming 250 process days).
1) Average Year Conditions
1962-1971 Avg. % Trash in field cane = 46.55%
Tons total trash/year = 675,000 x .4655 = 587,900 tons/year
(1-.4655)
Pushrake harvesting was assumed in the fields estimated
to yield 11% soil based upon field cane harvested.
Tons soil/year therefore amounts to 675,000 x .11 =
(1 -.4655)
138,900 tons/year
and Leafy Trash = 587,900 tons/year - 138,900 tons/year =
449,000 tons/year.
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[Mr. John Bersch on October 27, 1977, indicated that the fore-
going soil weights were on a dry weight basis, whereas all
trash weights were on a wet weight basis].
During 1972-1973, rudimentary trash screening and juice filter
mud disposal were incorporated at Honokaa and a portion of the
soil was estimated as removed along with the trash producing
the following residual waste loads:
Soil - 99,000 tons/year wet weight
Leafy Trash - 0 tons/year
Additional assumptions included 250 operating days per year
incorporation of Toft harvesting for 50% of the cane
expected to begin in 1976. It was also assumed that installa-
tion of a hydroseparator along with settling basins and res-
ervoirs would provide 90 percent removal of TSS, leaving a
final soil discharge of 4950 tons per year (wet). The average
daily discharge was computed to be 4950 tons 4- 250 days = 19.8
TPD (wet). Yearly Avg. lbs TSS/ton field cane = 9.9 (wet).
However, an alternate analysis was also cited at the meeting
of October 27, 1977. This alternate analysis is presented
below for comparative purposes.
2) Average Year Conditions (Alternate Analysis)
50% cane harvested by pushrake techniques = 337,500 TPY net
cane
50% cane harvested by Toft methods = 337,500 TPY net cane
Avg. % trash in pushrake field cane = 46.55%; that in Toft
field cane = 8.9%
Soil in field cane was estimated at 11% for pushrake cane;
that for Toft field cane = 3.2%
Field cane harvested by pushrake methods = 337,500 = 631,430 TPY
(1- .4655)
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Field cane harvested by Toft method = 337,500 = 370,500 TPY
(1-.0890)
Weight soil = 0.11 x 631,430 + .032 x 370,500 = 81,320 TPY
Soil remaining in effluent after hydroseparator treatment
(90% removals assumed) = (0.11 x 631,430) x .10 =6,950 TPY
= 27.8 TPD (wet)
Yearly Avg. lbs TSS/ton field cane = 13.87 (wet)
3) Wet Year Conditions
Avg. % trash in field cane estimated at 55.0%
Tons total trash/year = 675,000 x .55 = 825,000 TPY
(1 -.550)
Pushrake harvesting during wet year conditions was presumed
to yield 13% soil based upon field harvested cane.
Tons soil/year therefore amounts to 675,000 x.13 = 195,000
TPY and (1-.55)
Leafy Trash = 825,000 TPY - 195,000 TPY = 630,000 TPY
Rudimentary trash screening and juice filter mud disposal
which were incorporated into Honokaa were estimated to reduce
soil levels down to 139,800 TPY.
Additional assumptions included 250 operating days per year
and incorporation of Toft harvesting for 30% of the cane
expected to begin in 1976. It was also assumed that instal-
lation of a hydroseparator system would provide 90 percent
removal of TSS, leaving a final soil discharge of 140,000 TPY
x .10 x .7 = 9800 TPY (wet). The average daily discharge was
computed to be 9800 tons t 250 days =¦ 39.2 TPD (wet). Yearly
Avg. lbs TSS/ton field cane = 19.6 (wet). As for the Average
Year Conditions above, an alternate analysis was cited at the
meeting of October 27, 1977. This alternative analysis is
presented below for comparative purposes.
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4) Wet Year Conditions (Alternate Analysis)
70% cane harvested by pushrake techniques = 472,500 TPY net cane
30% cane harvested by Toft methods = 202,500 TPY net cane
Avg. % trash in pushrake field cane = 55%; that in Toft field
cane = 12.3%
Soil in field cane estimated at 13% for pushrake cane; that
for Toft field cane = 3.9%
Field cane harvested by pushrake methods = 472,500 = 1,050,000 TPY
(1-.55)
Field cane harvested by Toft method = 202,500 = 230,900 TPY
(1-.123)
Weight soil = .13 x 1,050,000 + .039 x 230,900 = 145,500 TPY
Soil remaining in effluent after hydroseparator treatment (90%
removal assumed) = (.13 x 1,050,000) x .10 = 13,650 TPY = 54.6
TPD (Wet)
Yearly Avg. lbs TSS/ton field cane = 21.3 (Wet)
5) Peak Conditions
Avg. % trash in field cane estimated at 60%.
Tons total trash/year = 675,000 x .6 = 1,012,500 TPY
(1-.6)
Pushrake harvesting during peak conditions was presumed to
yield 14% soil based upon field harvested cane. No Toft
harvested cane was assumed.
Tons Soil/Year therefore amounts to 675,000 x. 14 = 236,250 TPY,
(1-.6)
and Leafy Trash = 1,012,500 TPY - 236,250 TPY = 776,250 TPY
No credit was given in the John Eersch analysis for soil re-
duction due to rudimentary trash screening and juice filter
mud disposal as was the case for Average Year and Wet Year
conditions above. Furthermore, Mr. Bersch assumed 90% TSS
removal through the hydroseparator, but only 180 operating
days per year for Peak Conditions rather than 250 days per
year. The average daily discharge of TSS was computed to be
236,250 TPY x .10 = 131 TPD (Wet)
180 days
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EPA REGION IX ANALYSIS OF RAW LOADS
Production assumed to be 3000 TPD net cane.
1) For Average Conditions
20% soil anticipated to be removed during trash disposal.
Soil load = .12 tons/ton field cane = .24 tons/ton net cane.
50% of the cane was assumed to be harvested by conventional
means and 50% by Toft means.
Tons soil/day to WWTP = 3000 (.80)(.24)(.5) = 288 TPD dry
weight
95% removal of TSS predicted by primary treatment. Remain-
ing soil = 288 TPD x .05 = 14.4 TPD dry weight. Furthermore,
it has been presumed if only 2/3 of the Toft harvesters may
be delivered and in use by the NPDES Permit deadline, then
the effluent would contain 3000(.80)(.24)(.667)(.05) =
19.2 TPD dry weight.
The Avg. Daily TSS limit was established as 17.5 TPD ^ 35,000
lb/day TSS.
2) For Worse Conditions
15% soil anticipated to be removed concurrent with trash dis-
posal .
Soil load = .145 tons/ton field cane = .29 tons/ton net cane.
70% of the cane assumed to be harvested by conventional means
and 30% by Toft means.
Tons soil/day to WVJTP = 3000(.85)(.29)(.7) = 517.7 TPD dry
weight.
90% removal of TSS predicted by primary treatment leaves
51.8 TPD in effluent.
The Max. Daily Limit was established as 51.8 TPD 'v 110,000
lb/day TSS.
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RECENT DATA ON SOIL LOADS
Mr. Jean-Paul Merle during the EPA visit of October. 24-31,
1977 reported on the wet solids loads being removed from the
WWTP mud storage bin to field disposal. The transport trucks
have an 18 Ton capacity and the muds are assumed to contain
about 50% water. During the week of October 23, 1977, from 41
to 67 truckloads a day was recorded equivalent to 740 to 1200
TPD wet solids or 350 to 600 TPD dry solids. During the week
of October 16, an average of 45 truck loads per day was
recorded = 810 TPD wet solids ^ 400 TPD dry solids. From 26
to 39 truckloads were logged on a daily basis during the week
of October 9 = 470 to 700 TPD wet solids ^ 230 to 350 TPD dry
solids. Over the period of March 1 to 15, 1977, Honokaa Sugar
reported between 420 and 440 TPD TSS (dry weight) entering the
treatment works.
Mr. Jean-Paul Merle of Honokaa Sugar, in a report given at the
33rd Annual Conference of Hawaiian Sugar Technologists in
November 1974, indicated the new Honokaa WWTP was designed to
receive a wastewater flow of 4.5 mgd containing about 250 TPD
soil on a dry basis. In a later paper of November 1976, given
at the 35th Annual Conference of the Hawaiian Sugar Technolo-
gists, Mr. Merle stated that soil loads as high as 594 TPD dry
solids were entering the hydroseparator vs. the 250 TPD dry
solids that had been expected in 1974.
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V. AIR AND WASTEWATER POLLUTION CONTROL
AIR POLLUTION
Honokaa Sugar in 1973 was required to implement a two-phase air
pollution abatement program. Phase I called for a large overfire air
system to be completed by January 30, 1974. Phase II was to consist of
an additional fractionating dust collector to augment existing dry dust
collection units. Phase II was scheduled for completion by Hay 31,
1975, but was never implemented.
In November 1976, the State granted authority to the Company to
construct a new bagasse-fuel oil fired steam generation system inte-
grated with a multiclone dust collection system. The new boiler is
expected to be in full operation by late 1978. In accordance with this
action, the Company has requested a variance to continue operation of
the old boiler until such time that the new boiler is on line.
Applicable regulations under the Hawaii SIP require for the existing
Honokaa boiler that visible emissions not exceed 40 percent opacity and
that particulate emissions be limited to 0.4 lbs/100 lb bagasse burned.
Continous opacity instrumentation is available at the Honokaa power plant
control room. However, the opacity meter did not correlate well with
VEO readings made by the EPA on October 24, 1977 and again on October 29,
1977. On October 29, the opacity meter readings decreased while con-
current VEO readings made by NEIC-Denver demonstrated a substantial
increase. Visible emission tests were conducted by Mr. E. Struzeski of
NEIC-Denver on October 29, 1977, from 1332 to 1352 hours and from 1410
to 1423 hours. Another test was conducted on October 31, 1977, from
1109 to 1121 hours. All three tests showed that visible emissions were
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in excess of the allowable 40 percent opacity regulation (see attach-
ments). A number of high VEO's was noted for the Honokaa Sugar Company
including a series of 100 percent opacity readings on October 29, 1977.
Discussion with Mr. Glen Kawanishi of the Hawaii State Department of
Health located at Hilo, indicated in the past he also has experienced
100 percent opacity readings at Honokaa Sugar.
Fly ash from the Honokaa furnace is slurried into a relatively
large water flow and pumped to the main cane wash screen conveyor entering
the WWTP directly ahead of the grit separator.
WASTEWATER
Water Balance
A water balance including fresh water intake and the boiling house
operations with its auxiliary spray cooling pond is shown in Figure 1.
The power plant and boiling house condensers mostly control the amount of
water used at the Honokaa mill. The spray cooling pond is relatively
new. The rate of recycle of boiling house condenser water through the
spray pond is approximately 8,400 gpm (12.2 mgd). The objective is to
cool the condenser waters from 115°F down to about 95°F. From Figure 1
it can be seen that the boiling house is a heavier user of water than
cane cleaning. Fly ash sluice water is derived from fresh water supply
or excess condensates at the front end of the mill. Fly ash sluicing
uses around 1.4 mgd water.
A flow balance for the Honokaa wastewater treatment plant is provided
in Figure 2. The liquor pressed through the vacuum filter media and
otherwise known as filtrate is returned to the head end of treatment.
This waste stream has a typical flow of about 300 gpm (0.4 mgd) and
contains around 35,000 mg/1 TSS. The Honokaa facility presently pumps
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Fresh Water 220 psi
4.5 MGD
70°F
To
WWTP
Hydro
Generator
Reservoi r
Cane Cleaning
Plant
Fly ash stream
^1.4 MGD
Boiling House
Condensers
^ 3.2 MGD
IT
Pump
Figure 1. Water Balance
Honokaa Sugar Co.
Boiling House Operations
Power Plant, Cane Cleaning
x = 8400 gpm
90°F
115°F
Pumps
Boiling House
Reservoi r
SPRAY
I 1 k
1 1 Pc
Spray
Pond
Pumps
¦t
* *
:: * ::
POND
Overflow
Unauthori zed
Overflow
oo
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-------
20
treated wastewater for field irrigation amounting to about 1.4 mgd, but
is not recycling any clarified water to cane cleaning. If cane water
recycle were incorporated, the Company might find it necessary to dis-
charge boiling house condenser water rather than reusing this supply for
the boiling house and for cane washing. (Cane wash recycle however
could potentially reduce total plant waste loads discharged). Honokaa
Sugar plans to increase the size of its spray pond in the next few
months. During October 1977, WWTP discharge to the ocean was approxi-
mating 3.1 mgd, i.e. 4.5 mgd (3,100 gpm) from the WWTP minus 1.4 mgd
(1,000 gpm) for irrigation use.
Preliminary Screening
An overhead screen conveyor system with one-quarter inch openings
is used for final separation of trash and fibrous materials from plant
wastewaters. Cane wash waters and sluiced fly ash enter as two individual
waste streams onto the screen conveyor. The screenings are carried onto
a belt conveyor and then to an adjacent solids storage pile. Two mud
collection and transfer bins are situated directly adjacent to the
screen conveyor. One bin is used for juice filter muds and the other
for the solids removed at the WWTP. A solids overflow was noted from
the WWTP solids storage bin back to the belt conveyor off the cane wash
screen conveyor system. Flow of the cane wash and fly ash sluice stream
are reported by the Company as amounting to 2,200 gpm (3.2 mgd) and
1,000 gpm (1.4 mgd), respectively. Total flow into the WWTP is said by
the Company to average between 4.3 and 4.6 mgd (3,000 to 3,200 gpm) with
a maximum of 5.1 mgd (3,500 gpm).
Grit Separator
Wastewater is drawn off from the compartment under the screen
conveyor to a grit separator. The grit separator was estimated to be
-------
21
about 30 feet long by 18 inches wide. The grit chamber was incorporated
at the front end of the treatment works after the failure of DSM screens.
Heavy amounts of fly ash were observed in the grit separator. Two waste
return lines enter the front end of the grit chamber. One contains
filtrate from the vacuum filter and the other represents overflow from
the feed box of the vacuum filter. The grit chamber was designed by M.r.
John Bersch of Theo Davis & Company. Waste detention time in this unit
is minimal. Solids are removed from the grit separator by a slat con-
veyor which feeds into a chute and then to the main solids conveyor to
the WWTP solids storage bin. Honokaa Sugar Company personnel during the
week of October 23, 1977 reported that the grit chamber should be
removing about 6 percent of the incoming TSS to the WWTP. However,
visual observations indicated that removal of solids through this device
was poor. The Company has previously diverted waste flows around the
entire WWTP when the slat conveyor on the grit chamber has been down for
repairs (e.g. September 13, 1977). Standby facilities should be avail-
able to preclude this type of bypassing.
The grit separator unfortunately has never served as an adequate
substitute for the DSM screens. The DSM screens had been originally
designed to remove 50 to 60 percent of the TSS imposed upon the system.*
Failure of the DSM units was a severe setback for the Honokaa WWTP. The
grit chamber is considered essential by the Company to protect the
vacuum filter from abrasive solids. Honokaa Sugar was asked in October
1977 if Wedge Wire screens might be appropriate. The Company indicated
they did not care to experiment with screen systems following the fail-
ure of the DSM units. Mr. John-Paul Merle reported it is their
* See "Laboratory and Pilot Plant Study of Factory Wastewater", Jean-
Paul Merle, 33rd Annual Conference of Hawaiian Sugar Technologists,
November, 1974; "The Water Treatment System at Honokaa Sugar Company,"
Jean-Paul Merle, 35th Annual Conference of Hawaiian Sugar
Technologists, November 1976; and Report of NEIC trip made to Dorr-
Oliver, Inc. j Stamford, Conn., October 11, 1977.
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22
objective to achieve almost completely unattended operation of the
WWTP in the future; installation of more screens would require addi-
tional manual labor.
Waste flow is taken off the bottom front end of the grit separator
into a collector box and trough leading to the hydroseparator. Polymer
addition is made at the collector box. Honokaa purchases Nalco 7415-SC
polymer in a liquid form. Polymer feed rate at Honokaa is 40 lb/day as
dry solids which equates to around 1 mg/1 in a flow of 4.5 mgd. Honokaa
does not use polymer for vacuum filter improvement.
Hydroseparator
In March 1974, following laboratory treatment studies, an order was
placed with the Dorr Oliver Company of Stamford, Connecticut, for a 60-
foot diameter clarifier. (No engineering consultant is known to have
been employed by Honokaa Sugar for design of the clarifier). Dorr
Oliver supplied Honokaa Sugar with laboratory test procedures used in
sizing the clarifier. Based upon laboratory results, Dorr Oliver made
final sizing determinations. Dorr Oliver has emphasized that it per-
forms no engineering design; it sizes and makes available standardized
equipment based upon the needs of its client.
According to information received from Dorr Oliver in October 1977,
design flow for the Honokaa WWTP was 4.5 mgd giving a waste detention
time in the hydroseparator between 45 and 55 minutes. The settler is a
Dorr Oliver Cable-Torq Thickener, Type A, 60 feet in diameter. The unit
was reported to have a side wall depth of only about 7 feet and a depth
at the center well of around 11 feet. The Dorr Oliver handbook for Type
A thickeners cites 11 feet as the minimum available depth among its many
units available. Dorr Oliver stated based upon the assumptions above, that
the shallow thickener would be permissable. Capacity of the thickener
was reported to be 175,000 gallons. The overflow rate for the Honokaa
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23
2
thickener was calculated as 1,600 gpd/ft . The clarifier is a standard
center well feed unit with sludges being swept into a center cone at the
bottom of the settler and the sludges pumped to a vacuum filter. The
settler has a single set of weirs along the periphery of the tank. It
is common practice at Honokaa to pump part of the clarifier overflow to
field irrigation. During the week of October 23, a portable pump was
observed used for continuous application of clarifier effluent to field
irrigation. Field irrigation is estimated around 1.5 mgd leaving 2.5 to
3.5 mgd in the WWTP discharge going to the ocean. Last year, clarifier
overflow was recycled back to the cane washer but not this year because
of an abundant supply of water at the main mill.
The hydroseparator overflow in October 1977 was observed to be
heavily laden with solids. This indicates less than adequate sol ids
separation. Large quantities of flotable material and fly ash were
present on the clarifier surface. The flow into the hydroseparator had
undesirably high velocity and excessive surging was observed at the
center feed well of the clarifier. The clarifier is equipped with a
screw conveyor system which is designed to collect floating matter and
fly ash from the scum collection box and transfer this material to the
vacuum filter. It is believed that scum collection can be improved by
minor modifications.
Mr. Jean-Paul Merle in November 1976 described the Honokaa clari-
fier as having a sludge underflow rate of 150 to 500 gpm containing 10
to 30 percent solids. The Company in October 1977 indicated that the
clarifier mud flow rate approximates 400 gpm with about 20% solids going to
the vacuum filter. Polymer addition is said to improve solids concen-
tration of the underflow.
Honokaa Sugar and the Dorr Oliver Company have not provided the EPA
with specific treatment design criteria on waste removal efficiencies
and effluent characteristics. The record indicates the main objective
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24
of the treatment works has been to remove as much solids as economically
possible from the raw waste. Attaining a clear effluent has been a
secondary objective. Besides the lack of design data, there has been
relatively little reliable data on concurrent sampling of the influent
and effluent of the WWTP. Part of the reason is inaccessibility of the
treatment system to influent sampling.
Vacuum Filter
The Honokaa WWTP is equipped with a single, 10 foot x 20 foot Dorr
Oliver vacuum filter. The filtration surface is comprised of stainless
steel perforated screen of the same type as used in boiling house juice
filtration. Honokaa placed the order for the vacuum filter with Dorr
Oliver in August 1974 and the unit was installed around June 1976.
After it was becoming increasingly evident that the vacuum filter was
overloaded, the Company, in May 1977, placed an order with Dorr Oliver
for a second 10 foot by 20 foot vacuum filter. Dorr Oliver has commented
that stainless steel perforated screen compared to filter cloth gives a
much dirtier filtrate, although the stainless steel media permits consider-
ably higher filtration rates.
The Company had anticipated that the vacuum filter would provide
2
filtration rates up to 70 lbs dry solids/ft /hr, which is an exceptionally
high filtration rate.* The 10 foot by 20 foot vacuum filter has a total
surface area of 620 square feet. Assuming that the vacuum filter could
handle 70 lbs/ft /hour (which is not the case), the maximum permissible
solids load to the filter would be about 470 tons solids/day (dry).
Solids loads during heavy rainfall periods can easily exceed the 470 TPD
level as described earlier in this report. Honokaa Sugar presumed it
* From verbal discussions of October 24-31, 1977 with the Honokaa
Sugar Company.
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25
could meet EPA discharge limits if certain conditions were continuously
met including: maximum solids concentrations entering the hydroseparator
of about 20,000 mg/1; good polymer reaction; and the absence of mechani-
cal problems.
During the week of October 23, 1977, a relatively thin cake was
observed being collected off the rotary vacuum filter. Quality of the
filter cake varies greatly. At times, a thick cake is attainable together
with filtrate values as low as 7,000 mg/1 TSS. Moisture content of the
cake is usually around 52 percent. Filter cake is transferred over two
sets of belt conveyors to a small hopper which also receives solids from
the grit separator. The combined solids from the hopper are carried up
a main conveyor to the WWTP mud storage bin. The filtrate return to
the grit separator approximates a flow of 200 to 300 gpm and TSS levels
of 7,000 to 12,000 mg/1. The Company reports that polymer addition
would improve vacuum filtration but not enough to justify additional
cost of the polymer. The use of chlorine has been suggested in treatment
but Company personnel indicate not only is the chlorine demand high but
chlorine causes pH depression in already acidic waters and consequently
corrosion could be accelerated throughout the process circuits.
Additional Comments by Honokaa Sugar on Treatment
In the meeting of October 27, 1977, Company personnel indicated
that Theo Davis & Company, Ltd. did not wish to make additional expen-
ditures on air pollution abatement at either Honokaa or Laupahoehoe, but
such might be necessary in the future. The Company made claim for
pollution abatement costs of between $6.00 and $7.19 per ton sugar
produced which presumably is for both water and air. It is not known
what items may be involved in these calculations, but is is likely that
pollution costs include writeoffs for old plant and equipment. Never-
theless, a cost of say $6 per ton sugar, even if valid, would still
represent only about 2.2 percent of incoming revenues, assuming a current
sugar price of about 13.5 cents per pound.
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VI. UNAUTHORIZED DISCHARGE FROM BOILING HOUSE
AND BOILING HOUSE RESERVOIR
A schematic of the boiling house condensers, boiling house reser-
voir and accompanying spray cooling pond are shown as part of Figure 1.
During the week -of October 23, an unreported overflow was found origi-
nating from the boiling house reservoir. This overflow represents the
origin of an unauthorized stream finding its way to the ocean. A series
of pipes protruding from the base of the boiling house and buried in
heavy vegetation was observed alongside the stream. Direct discharge
from the boiling house to this stream is highly probable.
In May 1975, Honokaa Sugar reported that all unauthorized dis-
charges but one had been eliminated from the boiling house. The plant
was waiting delivery of a "positioner" which would control excess water
from the boiling house reservoir. The device was intended to reroute
all discharges to the 001 outfall. Caustic soda and/or acid are reported
to be used at the boiling house for cleanout and maintenance mainly of
evaporators and vacuum pans. Cleaning wastes are said to be routed to a
cesspool near the boiling house. Change in existing piping may be
necessary for controlling these waste flows.
The above stream emerges in the general vicinity of the 001 sampling
and flow measurement station about 100 yards northwest of the 001 par-
shall flume. A lower plantation road crosses both the 001 outfall
and the unauthorized discharge. The stream can easily be sampled and
flow rated just before it crosses under the plantation road.
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VII. NPDES REQUIREMENTS, SELF-MONITORING, SAMPLING
AND FLOW MEASUREMENT
NPDES PERMIT LIMITATIONS
The current-version of the NPDES Permit for the Honokaa Sugar Company
became effective June 2, 1977, and will expire September 30, 1978. The
Honokaa mill has a single authorized discharge, i.e., outfall 001. The
permit is based on a daily average mill processing level of 3,000 tons/day
of net cane, and contains the following important provisions.
Parameter Daily Avg. Limit Daily Max. Limit Monitoring Frequency
Flow -- -- Continuous
TSS 35,000 lb/day 110,000 lb/day 1/wk; composite
Settl. Solids 0.1 ml/1 0.2 ml/1 1/wk; grab
Additional Provisions
The effluent shall not contain any trash, bagasse, ash, clinker,
soot or filter cake at anytime, provided however that all such material
passing through a 0.5 mm screen shall be considered and measured as
TSS in the main discharge.
There shall be no discharge of floating solids or visible foam
in other than trace amounts.
The discharge shall not cause objectionable odors at the surface
of the receiving waters.
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28
For each day during which TSS are monitored, the permittee shall
record the number of tons processed of total field cane and of total net
cane.
A composite sample shall consist of no fewer than 8 individual
samples obtained at equal time intervals over the sampling period. The
volume of each individual sample shall be proportional to the discharge
flow rate at the^time of sampling. The sampling period shall equal the
discharge period, or 24 hours, whichever is shorter.
NPDES SELF-MONITORING RESULTS
Total plant discharge and waste loads compiled by the Honokaa Sugar
Company over the past 20 months are summarized in the following. Table
I presents average monthly data for the period February 1976 through
June 1977. Table II gives recent daily sampling results from July 6,
1977 through September 26, 1977. Honokaa Sugar Company is experiencing
great difficulty in meeting NPDES limitations.
SAMPLING AND FLOW MEASUREMENT AT THE HONOKAA 001 MONITORING STATION
The Honokaa 001 Outfall is measured a few hundred yards downstream
of the WWTP as the outfall crosses under a lower plantation road and
before the discharge reaches the ocean. The effluent ditch has a very'
high velocity and the Company near the end of 1976 constructed an
elaborate stilling device immediately ahead of a stainless steel 12-inch
parshall flume encased in concrete on the 001 outfall. Small waves were
evident on the approach to the flume, but no Whitewater was present. A
steel float and rod are provided in the control section of the parshall
flume attached to a device which transmits electronic signals proportional
to the head on the flume. The monitoring station is covered with a
protective shed and has been equipped with DC power. A seven-day flow
recorder was present together with a convenient chart for compositing
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29
TABLE I. SOLIDS AND BOD LOADS IN FINAL DISCHARGE
HONOKAA SUGAR MILL, PRIOR TO JULY 1977
Month
Flow
TSS
Settl. Sol.
BOO
5
(mgd)
(mg/1)
(lb/D)
(ml/1)
(mg/1)
(1 b/D)
Feb. 76
4.20
11,000
384,900
37
580
20,300
March 76
4.39
12,800
521,200
58
570 est.
22,600
April 76
4.75
11,100
440,000
est.
36
600
23,800 est.
May 76
4.80
7,230
289,500 est.
26
198
7,900 est.
June 76
4.00
4,820
160,900 est.
17
725
24,200 est.
Avg. Feb.-
-
June 76
4.53
9,400
359,000
35
535
19,800
July 76
4.54
3,370
127,600
10
637
24,100
Aug. 76
5.00
674
28,100
1.3
Sept. 76
4.10
285
9,740
2.8
316
10,800
Oct. 76
3.73
4,910
152,700
22
805
25,000
Nov. 76
4.58
9,220
351,900
34
885
33,800
Avg. July-
Nov. 76
4.39
3,690
134,000
14
660
23/00
March 77
5.02
3,530
147,800
31
1,190
49,600
April 77
5.22
2,903
126,300
30
795
33,300
May 77
4.29
639
22,900
7
1,590
56,900
June 77
2.29
541
10,300
2
_
Avg. March-
June 77
4.21
1,900
76,800
18
1,190
46,600
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30
TABLE II. SOLIDS AND BOD LOADS IN FINAL DISCHARGE
HONOKAA SUGAR MILL, JULY TO SEPTEMBER 1977
Flow
TSS
Settl. Sol.
Date*
(mgd)
(mg/1)
(lb/D)
(ml/1)
Comments
July 6
2.10
4,280
75,000
16
Extensive breakdowns
July 13
3.30
1,190
—
4
both July 13 and 20
July 20
2.30
362
--
2
resulted in highly
Mo. Avg.
-
1,940
—
7.3
erratic waste flow
patterns
Aug. 4
3.54
3,610
106,600
20
Aug. 10
2.66
8,410
186,700
40
Aug. 17
2.82
10,930
257,200
45
Aug. 24
2.59
7,490
162,000
27
Mo. Avg.
2.90
7,610
178,100
33
Aug. 31**
2.59
5,330
115,200
27
Sept. 7
3.30
7,200
198,300
25
Sept. 14
3.08
5,120
131,600
28
Sept. 21
2.80
812
19,000
5
Sept. 28
3.50
9,300
271,600
37
Mo. Avq.
3.05
5,550
147,100
24.4
3 Mo.
Avg.
2.84
5,030
121,100
22
* Date given is that on which the composite sample was initiated; e.g.
the composite sample gathered over July 6 to 7, 1977, is entered as
July 6.
** The Company has aggregated the August 31 to September 1 sample with the
September results rather than the August results.
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31
sub-samples proportional to flow. The approach section to the parshall
flume showed some flow disturbance but these effects were judged minor.
The parshall was considered acceptable. Flow through the 001 parshall
flume was reported by the Company as varying between 2.5 and 3.5 mgd.
Grabs for NPDES permit purposes are collected at the 001 location by
manual means every three hours and made into a daily composite sample on
a flow proportionate basis. The 24-hour composite sample normally
extends from Wednesday morning to Thursday morning each week.
ADDITIONAL SAMPLING LOCATIONS AT HONOKAA WWTP
One of the objectives of the NEIC-Denver inspection of October 1977
at Honokaa was to select tentative sampling locations for the purpose of
specifically determining waste removal efficiencies through the WWTP.
Establishing sampling points inside the treatment plant is difficult
because of the non-accessibility of waste streams and various inter-
ference factors within the system. It was ascertained that influent can
be sampled only in the flow upwelling at the very front end of the grit
separator. This particular location is illustrated in Figure 3. Two
lines from the vacuum filter enter near the head of the grit separator
and sampling must be conducted ahead of these interferences. Sampling
further downstream would not give representative results. The effluent
from the WWTP can be sampled at the main overflow box of the hydro-
separator which is also the point of irrigation water takeoff from the
Honokaa WWTP.
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32
Influent can be sampled manually in flow
upwelltng at entrance of grit separator
Filtrate and Overflow from V a c u
Influent from
Screen Conveyor
Stat Conveyor
Effluent
GRIT SEPARATOR. SIDE VIEW
Bottom
Compart
m e n t
at Screen
Grit
Chamber
Vacuum Filter
Return
Polymer
Addition
Collector Box
FRONT VIEW GRIT SEPARATOR ASSEMBLY
Figure 3 Suggested Sampling, WWTP Influent, Ho no k a a Sugar Co
-------
VIII. ANALYSIS OF HONOKAA WWTP DESIGN
Investigation of primary treatment at Honokaa Sugar started in
early 1973 with laboratory settling tests using 1000 ml graduate cyl-
inders. The laboratory procedures were apparently developed by Dorr
2
Oliver, Inc. Unit settling area expressed as ft /ton solids/day was
calculated from 'the laboratory data, and a safety factor of 20 percent
then applied. The test procedures called for 100 mesh screening of the
feed material to laboratory settling. Polymer at 1 to 3 mg/1, together with
lime, were found necessary for rapid solids settling. Besides floccula-
tion of soil particles, lime was determined to have good disinfectant
properties. The Company concluded that lime was too expensive for use
in treatment.
The Company conducted 24 laboratory settling experiments in 1973
and 21 additional experiments in 1974. Company calculation sheets for
the first 24 runs showed widely varying results. Settling area com-
2
putations, based upon WWTP design flow of 4.5 mgd, ranged from 715 ft
2
up to 6900 ft , equivalent to a hydroseparator having a diameter of 27
feet up to 83 feet. Unfortunately, the majority of the tests were
conducted at TSS concentrations less than 11,000 mg/1. The average feed
concentration for the 24 runs was only 12,000 mg/1, which corresponds to
a daily loading rate of 225 TPD. It was noted earlier in this report
that solids loads had been found in 1975 and 1976 to be in the range of
400 to 600 TPD dry weight, and even higher.
The 1974 lab settling tests generally showed lower settling rates
compared to the 1973 tests. The files of the Honokaa Sugar Co. indicate
some thought was given in 1974 that an 82 foot diameter thickener might
be necessary for a flow of 4.5 mgd and a solids content of 12,000 mg/1
in the incoming feed. The files also show recognition by the Company
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34
that waste flows were approximating 5.3 mgd, in other words, 0.8 mgd
higher than the 4.5 mgd being designed for. The Company was, however,
anticipating reducing water usage whereby the designed target waste flow
of 4.5 mgd could be reached. Nevertheless, based upon flow results
contained in a Company letter of March 19, 1977 to the Hawaii DOH, it is
noted for 39 monitoring days over the period of July 14, 1976 to Novem-
ber 30, 1976, that discharge flows exceeded the 4.5 mgd WWTP design flow
on 22 of these days.
Engineering design should be conservative when extrapolating from
laboratory settleability tests to full-scale settlers. Pilot scale
studies are preferrable to graduate cylinder or beaker tests for pre-
dicting full-scale requirements. Metcalf and Eddy, Inc., in "Wastewater
Engineering, Collection, Treatment, Disposal", McGraw-Hill, Inc., 1972,
recommend that preliminary settling evaluation should be conducted in a
container no less than 6 to 8 inches in diameter and equivalent in depth
to the full-scale sedimentation tank. For settling of discrete particles,
Metcalf and Eddy further recommend when using the test cylinder above,
that the critical settling velocity should be muliplied by 0.65 to give
design velocity in the full-scale unit. Also, detention time in the test
cylinder should be multiplied by a factor of 1.75 to 2.0 for scale-up to
full size.
An evaluation report was prepared by a representative of Dorr
Oliver, Inc. in January 1974 essentially based upon the 24 laboratory
settling experiments described above. This report indicated that the
size of a full-scale clarifier based upon the laboratory results, should
be roughly 45 to 60 feet in diameter. The report commented that settling
area requirements did not decrease with increasing solids concentration.
The report further estimated that wastewaters in the hydroseparator
would have a detention time between 30 and 45 minutes. This compares
to a range of 90 to 120 minutes minimum detention time commonly
used for wastewater settling. Mr. Richard Hunwick of Dorr Oliver, in a
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35
report appearing in Sugar y Azucar in March 1977, described the Honokaa low
detention type system as ... "more tempermental, i.e. less resistant to
shock loads, and (requiring) careful monitoring of the operation." Mr.
Hunwick also specified hydroseparator detention times of 1.5 to 2.5
hours when the cane wash recirculation ratio is low, which is the case
at Honokaa Sugar. In 1974, a pilot-scale hydroseparator 6 foot in diameter
by 8 feet in depth, and having a 1300 gallon capacity, was deployed by
Honokaa Sugar. .However, this unit was almost exclusively used in con-
junction with mud filtration experiments rather than developing settling
data.
From available evidence, the Honokaa Sugar Co.-Dorr Oliver approach
to waste settling has been optimistic. The sugar company and Dorr
Oliver have advised the EPA that waste treatment technology for the
Hilo-Hamakua "Coast sugar mills has been unique and complex. Yet the
decision was made to base full-scale settling requirements upon graduate
cylinder results and without the benefit of pilot testing. Liberal
design was employed and safety factors were relatively small in going
from laboratory to full-scale treatment. No consulting design engineer
appears to have been involved in these studies. Amounts of soil entering
the WWTP under heavy rainfall conditions appear to have been seriously
underestimated. This was partly due to the DSM screens preceding settling
having been discontinued in 1976. The Honokaa hydroseparator is extremely
shallow and does not permit good separation of the sludge blanket from
the quiescent settling zone. The Honokaa hydroseparator offers limited
opportunity for retaining and consolidating the sludge blanket. The
hydroseparator receives enormous amounts of TSS during runoff condi-
tions, i.e. up to 500-600 TPD dry weight, and with the more or less
conventional rake and scrapper mechanism, may not be capable of phys-
ically removing all solids from the bottom of the clarifier. If the
solids are not taken from the bottom of the settler, they must then
-------
36
escape over the overflow weirs. At the high clarifier overflow rate of
?
around 1,600 gpd/ft the solids must settle rapidly if they are to be
removed. High flow velocities are experienced at the center feed well
making quiescent settling more difficult. The treatment system also
lacks waste equalization which adversely impacts upon solids removal
efficiency.
Following feu'lure of the DSM screens in the treatment circuit,
Honokaa conducted experiments in earlyl976 with a rotary screen having
0.5 mm openings. Unfortunately, the rotary screen was placed on the fly
ash sluice stream and not the combined WWTP influent. The rotary screen
was discontinued after a short period because of alleged difficulties in
handling the screenings. It is not entirely clear why the rotary screen
studies were stopped. It is believed that appropriate data were not
collected for the rotary screen to adequately determine its performance
efficiency.
Laboratory filtration tests were conducted by Honokaa Sugar in 1973
using a 0.1 square foot leaf filter provided by Dorr Oliver, Inc. A
plant safety factor of 0.65 was employed with these tests. The Company
thinking, as exemplified in Mr. JeanPaul Merle's report of November 1974
before the 33rd Annual Conference of Hawaiian Sugar Technologists, was
that no more than 250 TPD of dry solids would be experienced at the
factory. With a vacuum filter of 10 feet by 20 feet giving a total
?
filtration area of 620 ft , it was anticipated that a filtration rate of
2
about 33 lbs. dry solids/hour/ft would be adequate at Honokaa. The
preliminary vacuum filtration work led to pilot plant testing in August
1974 with a 3 foot by 1 foot filter. Using stainless steel screening on
the vacuum filter, high filtration rates were achieved, although the
filtrate was relatively dirty. Mr. Merle, in his November 1974 paper
based upon the study results, found that filtration rates greater than
2
20 lbs dry solids/hour/ft were obtainable. In August 1974, the Honokaa
Sugar Co. placed an order with Dorr Oliver for a single 10 foot by 20
foot rotary vacuum filter.
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37
The Company, through 1975, continued to have difficulty in reaching
desirable filtration rates. In 1976, with the full-scale vacuum filter
in operation and polymers being added to the vacuum filter feed, filtra-
2
tion rates were obtained between 66 and 77 lb dry solids/ hour/ft .
However, these rates were demonstrated only over extremely short inter-
vals. At this stage, the Company recognized that solids loads could
peak as high as 600 TPD dry weight, and that a single vacuum filter was
insufficient. Subsequently, a second vacuum filter was ordered from
Dorr Oliver. The Company has indicated until a second filter is installed,
the underflow mud from the hydroseparator must be treated with a polymer
when operating under poor harvesting conditions. This prescribed prac-
tice was not being conducted during the week of October 23, 1977. In
the January 1974 evaluation report prepared by Dorr Oliver, the observa-
tion was made at that time that up to six 12 foot by 24 foot drum fil-
ters might be necessary for the Honokaa installation. Admittedly however,
this requirement was based upon preliminary filtration tests and the use
of filter cloth rather than stainless steel filtration media. Assuming
an optimistic filtration rate of 50 lb. dry solids/hour/ft using two 10
foot by 20 foot vacuum filters which would operate 20 hours during the
day, a maximum of 620 TPD solids can be handled through the filter
station. Two vacuum filters may not be adequate to cope with maximum
soil load conditions, especially if Honokaa processing rates were to
increase.
The laboratory and pilot filtration investigations showed that lime
added to the hydroseparator feed would aid in flocculation of the suspended
solids, decrease bacterial activity in the circuits, and also improve
vacuum filtration. During the investigations, bacterial growth seemed
to be a major problem. Failure of the DSM screens, for example, may
have been due not only to excessive wear, but aggravated by extensive
slime buildup. Liming also serves to reduce anaerobic conditions that
can occur through treatment, particularly at the bottom of the
-------
38
hydroseparator and in the clarifier underflows. Mr. Richard Hunwick of
Dorr Oliver, in his report appearing in Sugar y Azucar in March 1977 for
a Honokaa type treatment system, recommends the addition of lime to
increase pH levels to about 7.0 to 7.5. High liming up to pH 11 is
beneficial but generally not economical. The problem of low pH levels
in the Honokaa system has not yet been adequately recognized, but is
roughly proportional to waste detention and the amount of food or BOD
present. Secondary treatment and removal of BOD is indicated for the
future. Chlorine is a possible substitute for lime in controlling
bacteria at selected points in the plant, and deserves further atten-
tion.
-------
IX. SUPPLEMENTAL REFERENCES ON TREATMENT DESIGN
Mr. Allan Duvall reported in the late-1960's that the Ewa Plantation
Company and the Waialua Agricultural Company at that time were utilizing
relatively large hydroseparators 120 feet in diameter for treating their
~
sugar cane wastewaters . The desilted waters were directed to irrigation
of cane fields. The clarifier muds were conveyed to diked ponds which,
when filled, were allowed to dry and subsequently planted to cane. At
other factories, the desilted hydroseparator overflow was recycled for
cane cleaning. Hydroseparator overflow rates at the above installations
were about 3 ft. per hour, capable of removing silt particles down to
the 15 micron size.
Sunn, Low, Tom & Hara, Inc., in their draft report of May 25, 1973
to the Effluent Guidelines Division of the EPA, Washington, D.C., pro-
vided design criteria on waste treatment at both irrigated (dry) and
non-irrigated (wet) sugar cane plantations. For the non-irrigated planta-
tions which typify the Hilo-Hamakua sugar companies, it was advised that
the waste treatment clarifier not exceed a surface overflow rate of 1440
gsfd, and the solids loading be held to a maximum of 6 lb/ft2/hour.
(This same consultant, in preliminary design work for the Hilo Coast
Processing Co. in 1974, specified overflows as low as 4 lb/ft2/hour).
Clarifier tank depth was recommended as 15 feet, which would provide 8
feet of solids slurry storage and 7 feet of clear supernatant. It was
assumed there would be sufficient control of sludge withdrawal to pre-
vent gassification in the clarifier. Sunn, Low, Tom & Hara, Inc. also
recommended a holding pond for relieving the clarifier of excess mud and
an emergency pond for storing incoming wastewater. A maximum design soil
* "Hawaii's Hydroseparator Systems Transform Cane Cleaner Effluent3"
Allan R. Duvall, Paper believed to have been published in the late
1960 's. Location and data unknown.
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40
load of 1,380 TPD was predicted for a factory processing 3200 TPD net
cane. This soil load at a 52% moisture content equates to 660 TPD dry
solids. The consultant indicated a treatment plant designed for this
load would be overloaded less than 1% of the time.
In conversation with Dorr Oliver, Inc. representatives in Stamford,
Conn, in October 1977, it was affirmed that "some" consideration has
been previously given to the possibility of two-stage waste settling at
the Hilo-Hamakua Coast sugar mills in Hawaii. However, no further details
were available.
-------
ATTACHMENTS
-------
VISIBLE EMISSION OBSERVATION RECOPD
Company f-j evin <->4 Won <^'/xz^ , U¦ , Hi
Date
fa - 29 - 77
Time Start
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Inspector
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Comments
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-------
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-------
VISIBLC EMISF y-N ORPR7AT JOM R'-.VORD
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-------
MAP
Symbols
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Photographs: S&A File ( )
Enclosed ( ) None ( )
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