REPORT ON FIRST COMMERCIAL EVALUATION OF DRY CAUSTIC PmLIXG OF CLINGSTONE PEACHES (2)

by

Herbert E. Stone (1)

INTRODUCTION

Del Monte Corporation, i n cooperation with the Environmental Protection Agency under G r a n t Project No. 12060 HFY, investigated the commercial f e a s i b i l i t y of using the dry caust ic peeling process t o remove chemically softened peach pee l and t o r e t a i n it i n a manner which would allow i t s disposal as a so l id material . gently wiping the major portion of pee l from the peach halves with a se r i e s of uniquely designed s o f t rubber discs which ro t a t e and tumble the f r u i t . f a c i l i t a t e s the peeling. minimum amount of water -- removes any res idua l pee l remaining after the wiping action.

This process uses the pr inc ip le of

New equipment, spec i f i ca l ly designed f o r t h i s purpose, A s e r i e s of f r e sh water sprays -- applying a

Clingstone peach i s a major crop with an annual production exceeding 30 mill ion cases. Being a seasonal f r u i t , it cannot be s tored fo r any length of time. from only a few weeks, i n some areas, t o a maximum of three months.

The production period i s therefore r e l a t i v e l y short , ranging

The most common commercial peeling process f o r c l ing peaches u t i l i z e s a d i l u t e sodium hydroxide (caus t ic ) solution t o soften the peel. i s followed by large quant i t ies of f resh, potable water applied under high pressure t o dislodge and remove the peel and caust ic residues. The e f f luent from t h i s operation frequently contains r e l a t ive ly high mounts of dissolved and undissolved organic materials which do not lend themselves t o mechanical removal. Consequently, these wastes comprise a port ion of the l i q u i d eff luent from the plant .

This

Disposal of t h i s e f f luent with the resu l tan t organic and hydraulic loads which may be imposed on municipal o r p r iva t e ly owned waste treatment systems has frequently been a serious concern t o communities i n p lan t locations, as well as t o regulatory agencies.

(l)Manager, Environmental Protection, Del Monte Corporation, San Francisco, Cal i fornia

(2)This invest igat ion was supported by funds from the Environmental Protection Agency Water Qual i ty Office under Grant No. 1 2 0 6 0 ~ ~ ~ .

1

I n response t o t h i s concern, the food processing industry has completed a number of research pro jec ts whose prime goals have been determining means f o r reducing:

1) the generation of oxygen demanding substances (BOD, COD, e tc . ) which a re a na tura l component of the food; and,

the use of f r e sh water i n p lan t or processing areas where product qua l i ty and san i ta t ion requirements would not be adversely affected.

2)

One such pro jec t was car r ied out i n 1970 under EPA (formerly'Federa1 Water Qual i ty Administration) Research and Development Grant No. 12060 F&E e n t i t l e d "Dry Caustic Peeling of Tree F r u i t f o r Liquid Waste Reductions". (Reference #1) Under t h i s pro jec t , the National Canners Association Western Research Laboratory i n Berkeley, Cal i fornia , w i t h the assis tance of the Western Ut i l iza t ion Research Laboratory of USDA i n Albany, Cal i fornia , demonstrated the f e a s i b i l i t y f o r removing caus t ic softened peach pee l w i t h the aid of rapidly ro ta t ing , s o f t rubber discs , re ta in ing the s o l i d pee l separate from the l i qu id waste stream and removing the small amounts of res idual pee l and chemical residue w i t h markedly reduced volumes of f r e sh water.

On the basis of these p i l o t scale r e s u l t s , Del Monte Corporation offered a proposal t o the Environmental Protection Agency t o design, construct and permanently i n s t a l l equipment which would afford a commercial demonstration of the f e a s i b i l i t y for peeling c l ing peaches, removing and re ta in ing the pee l as a so l id waste and s ign i f i can t ly reducing the volume of f r e sh water normally used during t h i s phase of the preparation of peaches f o r canning.

EPA Research and Development G r a n t No. 12060 HFY was awarded on Apr i l I, 1971 fo r the purpose of p a r t i a l l y supporting the implementation of th i s proposal. Del Monte Corporation Plant No. 3, located i n S a n Jose, Cal i fornia , was selected as the s i t e fo r th i s demonstration in s t a l l a t ion .

Commercial s i ze equipment was designed by Del Monte engineers and constructed i n a company-owned machine shop and on the s i t e by p lan t personnel. of the design and i n s t a l l a t i o n are appended t o the f i n a l report which w i l l be avai lable shor t ly from EPA.

Detai ls

(Reference #6)

I n s t a l l a t i o n of the experimental peeler was completed during the ea r ly summer of 1971. a need f o r adjustments and minor modifications of the peeler and a conveyor be l t . Continuous, th ree-sh i f t operation of the experimental peeler was i n i t i a t e d on August 10, 1971. The evaluation continued through September 17, the close of the 1971 c l ing peach canning season.

A b r i e f t e s t period under production conditions indicated

The commercial s i ze equipment was patterned a f t e r the NCA-USDA model and was scaled i n s i ze t o pee l 10-12 tons per hour of p i t t e d c l ing peach halves equal t o approximately 25% of the t o t a l p lan t production.

2

A sub-project i n the evaluation of the new peeling process f o r c l ing peaches was the b io logica l treatment of water used as a f i n a l r i n se a f t e r pee l removal. Concentrated waste water was segregated from a l l other waste flows and piped d i r e c t l y t o an ex is t ing high r a t e t r i c k l i n g f i l t e r biological treatment system which had been used i n previous s tudies and i s described i n greater d e t a i l i n other reports . Work under t h i s phase of Project 12060 HFY was supervised and conducted by personnel from the National Canners Association Western Laboratories i n Berkeley, California.

(References ( 2 ) ( 3 ) )

CONVENTIONAL PEELING

I n the conventional peeling method, (Figure No. 1) p i t t e d peaches a re turned so tha t the p i t cavi ty i s facing downward (termed "cup down") on a LaPorte metal ( l i n k chain) conveyor b e l t immediately p r i o r t o enter ing a par t i t ioned tank. with a d i l u t e solut ion of hot sodium hydroxide ( caus t i c ) . The conveyor c a r r i e s the f r u i t through the second steam heated holding sect ion where chemical act ion on the skins i s completed. i s car r ied under a se r i e s of high pressure water sprays where pee l and caus t ic residue a re removed and flushed in to f loo r drains f o r disposal. I n the operation a t Del Monte's Plant No. 3, as many as 20 banks of sprays may be used t o complete the peeling. However, only the f i n a l s i x spray headers apply f r e sh water w i t h the remainder divided i n t o groups of sprays using recycled r in se water i n a countercurrent manner.

I n the f i rs t sect ion of the tank, peach skins a re sprayed

I n the l a s t section, the fruit

Control of chemical peeling i s achieved by adjustments of the sodium hydroxide concentration, temperature of the solut ion and speed of the conveyor t o allow f o r react ion time of the hydroxide solut ion on the skin. If necessary, a food grade wetting a.gent may occasionally be added t o the caus t ic solut ion t o f a c i l i t a t e removal of tenaciously adhering peels on some v a r i e t i e s of f r u i t .

Following the f i n a l s e r i e s of f r e sh water sprays, the peach halves a re again inverted so that the p i t cav i ty i s facing up as the f r u i t i s conveyed pas t another v i sua l inspection s t a t i o n where defects o r other lower qua l i t y peaches a re removed fo r trimming, diversion t o an a l t e rna te s t y l e of product or discarded. imperfect halves, green f r u i t , e tc .

Defects include p i t fragments, pee l residues, blemishes,

DRY CAUSTIC PEELING

Peach halves peeled by the experimental dry caus t ic method (Figure 2) a r e subjected t o the iden t i ca l sodium hydroxide solut ion concentration, temperature and holding period as the conventional method described above. However, p r i o r t o r ins ing w i t h water, peach halves a re diver ted from the LaPorte conveyor onto a cross conveyor rubber b e l t which provides d i s t r ibu - t i o n over the f u l l width of the dry caus t ic peeling uni t , described i n greater d e t a i l below. From the peeling unit, peaches s l i d e down a short chute in to a tank of water from where they a re elevated by a link chain s la t conveyor t o another conveyor f o r r e tu rn t o the inspection b e l t s , described previously.

3

T SODIUM MDROXI DE SOLUTION

VALVE r FRESH WATER METER

I SPRAY RINSE

SECTiON SHAKER

INSRECTION BELT (

LSODIUM HYDROXIDE PEELER TANK

RINSE WATER TO 1- MUNICIPAL SEWER

SAMPLE BOTTLE (rrfrigeroted)

Figure 1. Schematic-conventional l iqu id caustic peeler

SODIUM HYDROXIDE SOW TlON

8/-vALvE

FRESH WATER METER k

TO CUPUP

INSPECTION ELEVATOR SHAKER AN0

SODIUM HYDROXIDE PEELER TANK

PEEL SOLIDS

HOPPER e T O WASTE

PUMP

SAMPLER 1

RINSE WATER

TREATMENT SYSTEM --t TO BIOLOGICAL

SAMPLER /m

BELT

Figure 2. Schematic-dry caustic peeler

Once pas t t h i s inspection s ta t ion , no attempt i s made t o keep "dry" and conventionally peeled peaches separate o r t o d i f f e ren t i a t e i n any subsequect grading, preparation, canning or processing operation.

DElvlONSTRATION EQUIPMENT

The dry caus t ic peeling uni t consis ts of a frame -- s i x f e e t wide by t en f e e t long -- mounted on adjustable legs. A se r i e s of 39 s t a i n l e s s s t e e l sha f t s a re mounted across the six-foot dimension. Specially designed, s o f t rubber discs (food grade rubber) a re mounted on each shaft: A chain dr ive from a 7-l/2 H.P. vari-speed U. S. Motor t o sprockets a t the end of each shaf t provide pos i t ive ro t a t ion of the discs . cleans the peach halves and t ranspor t s them across the top of the peeler.

The ro ta t ing act ion

Peeling i s achieved by the gent le abrasion of d i scs ro ta t ing a t a speed of approximately 325 rpm. diameter s i ze incorporates a f l ex ib l e flanged edge which gent ly removes the softened pee l on peaches t rave l ing i n a s ingle layer on the tops of t he discs. spec i f ic shaf t s and s t r a t eg ica l ly placed t o inver t peach halves which may turn over i n t o a "cup down" posi t ion as a result of the tumbling action. It is , of course, necessary t o expose the pee l port ion of the peach t o the abrasive act ion of the discs.

Discs a re of two types. The l a rge r 4-1/4 inch

The smaller 2-3/4 inch diameter stub discs a re mounted on

Figure No. 3 i s an engineering diagram of the two types of discs. conrplete d e t a i l s regarding configuration, dimensions and placement of discs may be found i n the engineering drawings appended t o the EPA repor t on Project 12060 HFY (Reference 6).

More

Discs and spacer sections between d iscs are c a s t as one piece i n the mold. A project ion or "key" i n the center hole i s a l so an in t eg ra l portion of each disc. pos i t ive dr ive of the disc. p i l o t model which used p l a s t i c spacers between the discs and depended upon f r i c t i o n t o drive the discs.

The "key" f i t s i n t o a s l o t on the sha f t , thereby achieving This contrasts w i t h the previous year 's

As noted above, movement of the peach halves i s achieved by discs ro ta t ing i n the same d i rec t ion as the flow of f r u i t . Duration of time on the peeler un i t i s control led by adjustment of the height of the discharge end over the feed end. The discs , i n e f f e c t , are pushing the peach halves up a s l i g h t inc l ine . feed t o discharge end of the peeler was found optimum fo r the va r i e t i e s of peaches processed by the p lan t during the 1971 canning season.

A 17-18 inch r i s e over t he ten foot length from

Peel and caus t ic residues f a l l between the ro t a t ing rubber discs i n t o a conical ly shaped tank from where they are pumped through a separate 4" diameter pipe i n t o a large hopper i n the plant yard. t h i s hopper i s combined with so l id wastes from other f r u i t preparation operations and i s hauled by t ruck t o an approved land disposal s i t e . )

(The waste from

6

rd 1'' R. (typical)

CROSS-SECTION DETAIL

L , K g R. (typical)

CROSS -SECTION DETAIL STUB DISC

FLANGE DISC Material: Black Rubber - 50 Durometer-Food Grade

Figure 3 . Rubber Disc D e b i l

The chemically softened peel material , as it i s removed from the peach halves, i s a viscous s lu r ry or semi-solid which can be pumped eas i ly by commercially avai lable conventional cement type pumps. the primary co l lec t ion tank was drained by manually s t a r t i n g the pump 2-3 times per hour. of peach pee l s lur ry .

I n t h i s project ,

Each draining represents approximately 60 cubic f e e t

Three (3) manifolds of f r e sh water sprays, mounted above the l i n k chain elevator conveyor, remove pee l and caust ic residues and provide the only f resh water r ins ing necessary on the "dry" peeled f r u i t . a l s o serve as make-up water f o r the tank i n t o which the f r u i t s l i d e s following the peeler section. Four (4) spray nozzles, each nozzle del iver ing approximately one gallon per minute of f r e sh water, are mounted on each manifold and posit ioned t o achieve f u l l coverage of the elevator conveyor width. An automatic sensing device maintains the proper l e v e l of water i n the tank following the peeler. Rinse water from t h i s tank i s piped t o the b io logica l treatment system being t e s t ed by NCA personnel as a sub-project of the peeling evaluation.

These sprays

A " I C A L PROGRAM

An extensive ana ly t ica l program was conducted t o evaluate the effectiveness of the dry caus t ic peeler f o r removing the pee l and re ta in ing the s o l i d mater ia l as a separate en t i ty . from the "dry" method were compared w i t h those from conventional peeling methods. Figure No. 4 i s a schematic of the sampling points fo r these parameters. Center and the NCA Laboratory and the schedule f o r each. of pee l and r in se water a r e those deemed most s ign i f icant .

Character is t ics of the waste r in se waters

Table I l i s t s analyses conducted i n the Del Monte Research The cha rac t e r i s t i c s

A s indicated i n the schedule, r inse water charac te r i s t ics were determined on both 24-hour composite samples col lected da i ly and on a se r i e s of hourly grab samples col lected on two operating days each week during the pro jec t period. completion of laboratory analyses during the normal work week insofar as possible.

The schedule was adjusted t o allow f o r i n i t i a t i o n and

Automatic sampling devices, i n s t a l l e d on r inse water discharge l i n e s from both peelers , were act ivated by timers which opened a valve allowing air t o "push" a measured quant i ty of r inse water from each sampling s t a t ion through p l a s t i c tubing i n t o individual p l a s t i c bo t t l e s inside a conventional household s t y l e re f r igera tor , located adjacent t o the dry caust ic peel ing uni t . An eight-ounce sample, drawn once per hour, was selected a s t he quant i ty and frequency of sub-sample f o r each composite. The reasonably uniform volume of water used i n t h i s operation and the s imi la r ly uniform flow of peaches d id not require more frequent sampling or necess i ta te attempts t o catch subt le var ia t ions. Approximately 2-1/2 gallons of composite sample were col lected da i ly from each l i n e . thoroughly before t ransfer r ing approximately one gallon t o another clean p l a s t i c b o t t l e f o r t ransport t o the Del Monte laboratory. The l a rge r composite sample bo t t l e s were then drained, r insed several times w i t h f r e sh water, drained again and returned t o the r e f r ige ra to r f o r col lect ion of the next 24-hour composite sample.

The composite b o t t l e was shaken

8

DRY PEELER DISC SECTION

-RINSE TANK

-PUMP WASTE h

TRICKLING

TREATED WATER OVERFLOW - TO SEWER

WET WELL SUMP /

FVALVE L - FLOW METER

SPRAY RINSE SECTION r

FLOW METER

WASTE WATER STREAM

CONVENTIONAL LIQUID CAUSTIC PEELER

/PUMP

t

I

DRY CAUSTIC PEELER

IDENTIFICATION OF SAMPLING POINTS:

I, Rinse water from conventional commercial peeler 2, Rinse water from experimental dry caustic peeler 3, Peel slurry from experimental dry caustic peeler 4. Influent to trickling f i l ter 5,6 t 7 Intermediate sampling ports in trickling

filter (no sampfes coffecfedj 8, Final effluent from trickling filter

Figure 4. Schematic diagram of sampling points

TABLE I - ANALYTICAL PROGRAM

EPA Project - 12060 EFY

Chemical Analysis Required/Sampling Station

Anal"

BOD5 (Total) ~

BODT (Soluble)

COD (Total)

COD (Soluble)

Total Solids

Suspended Solids

*

Volatile Suspended Solids

Kjeldahl Nitrogen

Ni t r i t e - Nitrogen

Nitrate - Nitrogen

..

Total Phosphate

Ortho Phosphate

Alkalinity (Total)

Dissolved Oxygen

Temp. (OC)

Footnotes:

(1)

24C

ac

G

Sampling s ta t ions are described on following pages and are ident i f ied on attached schematic diagram.

re fers t o a 24-hour composite sample which is composited with t i m e during an operating day.

re fers t o an 8-hour composite sample which is composited with time during an operating sh i f t .

re fe rs t o a random grab s-le collected once during an operating day for a l l sample s ta t ions except s ta t ions l b & 2b. samples are t o be collected hourly throughout an operating s h i f t with the analysis required on each individual grab sample.

For s ta t ions lb & 2b, grab

10

A l l samples analyzed at the Del Monte laboratory were on f r e sh mater ia l which had been re f r igera ted fo r 24 hours or l e s s . Samples were s tored i n an insulated container during the approximately one hour automobile dr ive from plan t s i t e re f r igera tor t o Research Center laboratory bench.

Peel loss on the fruit f o r both ''dry" and conventional peeling methods was determined by comparing weights f o r a random select ion of 100 peach halves, before exposure t o the sod im hydroxide solution, and another 100 randomly selected halves a f t e r peeling and rinsing. Peach halves from each peeling method were weighed by t ra ined plant personnel, approximately every half hour throughout the operating day during the duration of the'demonstration project . For c l a r i f i c a t i o n , it should be noted t h a t the plant has two completely separate, but ident ica l , conventional peach peelers . During t h i s pro jec t , one peeler was used as the "control" f o r evaluation of conventional r inse water charac te r i s t ics , water volume measurements and pee l loss determinations. Discharge of r inse water from this peeler was mixed w i t h other l i q u i d waste streams from the plant.

A portion of the p l an t ' s second peeler was used for t h i s demonstration project and only those peaches and r in se waters which were associated w i t h the experimental un i t a re included i n the data and discussion. 25% of the p lan t production (10-12 tons per hour) was peeled by the dry caust ic method.

Approximately

With the exception noted below, a l l ana ly t ica l procedures were i n accordance with those l i s t e d i n "Methods for Chemical Analysis of Water and Wastes - 1971 Edition" as prepared by the Water Qual i ty Office of EPA. procedure as outlined i n "Standard Methods fo r the Examination of Water and Wastewater" - 13th Edition, was followed.

The BOD

Interference of na tura l pect in i n the f r u i t prevented use of the conven- t i o n a l methods fo r separating soluble and suspended or co l lo ida l f rac t ions of matter i n the wastewater samples. samples was deemed necessary p r i o r t o determining soluble BOD and soluble COD.

Consequently, pretreatment of t he

A se r i e s of experiments developed the following procedure:

Wastewater samples were f i l t e r e d through diatomaceous ear th , followed by f i l t r a t i o n through Whatman No. 42 f i l t e r paper and ult imately, centrifuging at 2,000 rpm f o r 20 minutes. was reasonably c l ea r and considered su i tab le fo r soluble BOD and soluble COD determinations.

The resu l tan t supernatant

Composite samples f o r analysis of peel cha rac t e r i s t i c s were made by combining hourly col lect ions of a uniform quant i ty of pee l s lu r ry i n t o a s ingle one gallon container. This container was held inside a r e f r ige ra to r u n t i l t ransfer t o the Del Monte laboratory the following morning, along with composite and hourly samples of r inse water. (There was, of course, no comparable so l id waste sample from the conventional peeling method, as i n the l a t t e r instance, a l l pee l is flushed i n t o the l i qu id stream from where it cannot be physically separated.)

11

Tables 11, I11 & I V summarize r e s u l t s of composite analyses. the series of hourly grab samples may be found i n the EPA report on the project . They confirm the composite sample data. (Reference 6)

Results on

The sub-project evaluating poten t ia l benefi ts of biological treatment of the r in se water from the dry caust ic uni t used concentrated waste water segregated from a l l other l i qu id streams and piped d i r ec t ly t o the t r e a t - ment system. i n the EPA report on t h i s project. r inse water was an ex is t ing high r a t e t r i ck l ing f i l t e r which had been used i n previous s tudies and i s described i n greater d e t a i l i n other reports (References 2 & 3). i n Figure 5.

A f u l l description of the treatment procedure may be found Briefly, the system t h a t t r ea t ed the

A schematic diagram of the system i s shown

To provide f o r a na tura l up-draft of air thro.ugh the treatment column, air po r t s were in s t a l l ed around the base of the tank. sections were welded around the tank space a t 20 degree in te rva ls , making a t o t a l of 18 air ports.

Four inch pipe

The polyvinyl chloride p l a s t i c used i n the t r i ck l ing f i l t e r i s known as Surfpac, a regis tered t rade name of the Dow Chemical Company. Modules of 19~21x39 inches, each with 27 square f e e t of surface area per cubic foot and a volumetric void r a t i o of 0.94 were welded i n a honeycomb pat tern.

A composite 24-hour sample of the e f f luent from the t r i c k l i n g f i l t e r was col lected each day. each day. laboratory. were those l i s t e d i n "Methods f o r Chemical Analysis of Water and Wastes - 1971", prepared by the Water Qual i ty Office of EPA. The BOD procedure, as outlined i n "Standard Methods f o r the Examination of Water and Waste- water", 13 Edition, 1971, was followed. determine COD values. (Reference 5)

Two hour grab samples of the inf luent were a l so taken

Procedures f o r so l ids , nitrogen and phosphorus determinations Both s e t s of samples were frozen u n t i l analyzed a t the NCA

The Jeris method w a s used t o

Tables V I 1 and V I 1 1 summarize ana ly t ica l data obtained during two sampling periods.

DISCUSSION

Inspection of the data i n Tables I1 and 111, I V , V, & V I , supports some of the projections made f o r t h i s demonstration evaluation of "dry caustic" peeling of clingstone peaches:

1) Removal of the pee l and i t s segregation as a so l id waste reduced the pounds of waste per ton of fruit t h a t would otherwise be present i n the l iqu id e f f luent from the plant .

Table V I summarizes the pH and per cent t o t a l so l ids f o r 8-hour composite samples of pee l waste col lected during the demonstration period.

2) Substant ia l reductions i n water volumes required f o r t h i s operation a re possible.

12

Sample No.

IA 2A 3A 4A SA 6A 7A 8A 9A

1OA 1IA l 2 A

14A 15A 16A 17A 18A 19A 2oA 21A

w' 1 3

COD mg/l

4785 7290 8015 9895 8030 3435

11,305 5410 5350 3725 3200

4300 4325 4095 2965 5490 2670 4820 5910 6965

--

Average: 5600

Analytical Data - 24-Hour Composite Samples Dry Caustic Peeling Process - Cling Peach Rinse Water

2190 3820 5770 6170 3860 2890 8655 -- -- 2405 2365

2485 2375 2720

4545

--

-- 2150 4000 -- 3540

3750

BOD/COD

0.46 0.52 0.72 0.62 0.48 0.84 0.77

0.65

0.58 0.55 0.66

0.81

-- -- 0.74 --

-- 0.83

0.83

0.51

0.66

--

T o t a l Solids mg/l

5345 7010 8465 7825 6800

7160

5180

4205

4320

3930 4290

4470 4085 3990 3895

--

-- -- -- -- -- 5400

Suspended Solids A

-- 1650 2925 3550 3630 1630 2860 2450 2170 1150 2200

2300 2300 1650

--

2310

2670 --

2850 2700 2750

21r30

Total Ni t r i te N

-- -- 110.7 -- 156.9 < 0.02 108.6 -- 122.6 --

-- -- -- -- -- --

119.8 < 0.02 86.2 -- -- --

108.6 < 0.02 92.5 -- -- --

118.4 < 0.02

110.4 -- 116.5 -- 106.5 0.2 117.0 < 0.02

-- --

113.5 < 0.02

Total Ortho Alkalinity P

7.9 -- 10.0 -- 15.4 0.8 10.1 --

-- --

-- -- -- -- -- -- 5.0 <0.1 2.3 -- -- -- -- -- 4.9 2.2 4.9 -- -- -- 3.6 1.6

2.8 0.3 12.0 -- 5.2 3.2 6.7 3.0

-- --

-- 4 3 5 4.56 4.55 4.90 5.35 4. glc 4.89 5.10 5.85

4.73 4.70 4.88 4.78

--

-- -- -- -- -- 515 4.30 7.0' 1.6

Sample No.

lB 2B 3B 4B 5B 6B 7s 8B 9B 10B 1 l B

w 12B * 13B 14B 15B

17B 18B 19B 20B 21B

1 6 ~

1680 1305

1445 2030 1145 1415 1180 1335 1295 1650

2060 1170 1820 3275

1135 905

1100 1435

--

--

--

Average 1520

BOD/COD

0.51 0.61 -- 0.64 0.42

0.72 0.69

-- -- 0 ..76 0.65

0.61 --

0.71 0.63 -- --

0.73 0.78

0.75

0.65

--

TABLE I11

Analytical Data - 24 Hour Composite Samples Conventional Peeling Process - Cling Peach Rinse Water

Total Solids mg/l

2725 2165

2600 2525 2000 1910 2275 2225 2160 2680

--

-- 3125 2100 2540 4135 -- -- -- -- -- 2510

Suspended Solids ma/l

675 450

1250 --

1020 525 570

1350 425 250 800 -- -- 750 200

1340

700 300 710

1000

725

--

Total * N ma/l

36.4 25.2

35.7 39.9

--

-- -- --

35.0 32.2 -- -- 47.6 29.4 -- 56.0 -- 31.9 29.1 22.4 35.7

35.1

Ni t r i t e Nitrate

w7l lggfjl

< 0.02 0.3

Total Ortho Alkal ini ty P

8.91 7.62 5.70 6.85 6.51 7.11 6.92 6.80 8.32 6.40 6.59

6.21 6.20

6.00

--

6.70

-- -- -- -- -- 2.9 0.6 430 6.90

TABLE I V

COMPARISON OF WASTE EFFLUENT STRENGTH ANALYTICAL DATA

COD - D r y Caustic

Range( ppm) Avg . ( ppm)

2670-11,300 5600 Conventional gio-3275 i520

BOD -5 2150-8650 3750 Dry Caustic Conventional 700-1260 , 940

Suspended Solids

Dry Caustic 1150-3630 2430 Conventional 200 -1700 780

Total Solids D r y Caustic 3900-8450 5400 Conventional 1910-413,O 2510

Total Nitrogen Dry Caustic 86.16-156.91 110.32 Conventional 22.42- 47.63 35.14

Total Phosphate Dry Caustic 2.32-15.39 6.98 Conventional 0.69- 9.25 2.88

Alkal in i ty D r y Caustic 372-619 514 Conventional 374 -488 430

PH Dry Caustic 4 -35-5 085 4 .gO Conventional 5.70-8.90 6.85

15

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16

TABLE V

COMPARISON OF WASTI?, GENERATION*

Water Use

D r y Caustic Conventional

D r y Caustic Conventional

BOD, Dry Caustic Conventional

Suspended Solids

D r y Caustic Conventional

Total Solids

Dry Caustic Conventional

* Average Strengths.

17

4.2 lbs/ton 10.8 lbs/ton

2.8 lbs/ton 6.7 lbs/ton

1.9 lbs/ton 5.6 lbs/ton

4.0 lbs/ton 17.8 lbs/ton

(1) Analyt ical Data - 8 - ~ o u r Composite Samples Dry Caustic Peeling Process - Cling Peach Peel Solids

Sample No.

1s 2s 3s 4s 5s 6s 7s 8s 9s

10s 11s 12s 13s 14s 15s 16s 17s 18s 19s 20s 21s

Total Sol ids (%>

7.1 9.2 7.8

10.1 10.2 8.5 9.6

9.0 10.5 10.4 10.7 10.5 11.0

--

10.9

7.4 -- --

11.2 11.0

pH

-- io . 62 8.73

9.85 9.12

9.00 9.45

9.50 9.48

10.50 10.55

10.32

--

--

Aver age : 9.7 9.75

Footnote: (') Peel so l id s data f o r day s h i f t only. Spot checks during night s h i f t indicated similar resu l t s .

18

TABLE VI1

SUMMARY OF TRICKLING FILTER DATA

Sampling Period - 8/24 - 9/9 P a m e t e r Influent Effluent

PH 6.2 5 -8 Suspended Solids, ppm 1990 2440 Volatile Suspended Solids, p p m 1920 2360 COD, PPm 5580 4340 BOD, m 3490 2940 Nitrogen, Total, ppn 361 415 phosphorus, Total p p m 8.0 Lbs. COD/lOOO Ft3/Day 36; *9 282 Lbs, BOD/lOOO Ft3/Day 227 191

TABLE VI11

SUMMARY OF TRICKLING FILTER DATA

Sampling Period - 9/10 - 9/22 Parmet er ‘Influent Effluent

PH Suspended Solids, ppm

5 .4 5 .3 2620 3100 -

Volatile Suspended Solids, p p m 25 20 2960 3750 2760 160

COD, Ppm BOD, PPm Nitrogen, Total, ppm 220

;E Phosphorus, To al, ppm

# BOD/1000 Ft3/Day # COD/lOOO Ft 5 /Day 15.1

353 251

13 .9 244 179

19

Fresh water sprays on the demonstration un i t applied a seasonal average of 13 gallons per minute versus approximately 125 gallons per minute f o r a,n equivalent mount of f r u i t i n the conventional peeler. These ca lcu la te t o approximately 90 gallons of water per ton of peaches i n the dry caust ic peeler and 850 gallons per ton of peaches i n the conventional peeler.

3) Sl igh t ly lower pH l eve l s f o r 24-hour composite samples of r in se water from the "dry" peeler indicate removal of caust ic residue i n the segregated so l id pee l s lurry.

4) Peaches peeled by the "dry" process exhib i t s l i g h t l y grea te r than average weight l o s s than those from the conventional peeling method (7.8% vs. 6.6%). these differences can be corrected. Specif ical ly , the concen- t r a t i o n of sodium hydroxide solut ion i s probably higher than necessary fo r the "dry caustic" peeling method and r e s u l t s i n grea te r softening of the pee l and sub-dermal layers than would be necessary i n f u l l commercial development of the method. sodium hydroxide solut ion concentration could not be decreased, as 25% of the p l an t ' s non-experimental peach production used t h i s same spray sect ion and any s igni f icant change i n concentration would have resu l ted i n an unsat isfactory peeling under conventional production methods. )

However, it i s believed the causes f o r

(The

Another possible f ac to r contributing t o the grea te r pee l loss on the "dry" peeled peaches was the addi t ional handling which these halves received. The act ion of the diversion bar, shear- ing halves off of the LaPorte b e l t , undoubtedly removed some f lesh from the center port ion of the peach. commercial un i t w i t h a s t ra ight flow of f r u i t would preferably not have t h i s diversion and i t s consequent abrasive action.

A fu l l - s ca l e

5) During the f i rs t s e r i e s of t e s t s i n the t r i c k l i n g f i l t e r , COD i n the r in se water was reduced 22.2% and the BOD by 15.8%. During the second se r i e s , i n which nitrogen and phosphorus were added, t he COD reduction was 3l.@ and the BOD reduction w a s 28.5%. terms of pounds of COD or BOD removed per 1,000 cubic f e e t per day, the f i l t e r removed 81 pounds of COD and 36 pounds of BOD when only nitrogen was added. When nitrogen and phosphorus were added, the f i l t e r removed 109 pounds of COD and 72 pounds of BOD pe r 1,000 cubic f e e t per day.

I n

It would appear t h a t the improved performance by t h e t r i c k l i n g f i l t e r can be a t t r i bu ted a t l e a s t i n p a r t t o the addition of phosphorus as t h i s w a s the only major difference during the two tes t runs. sampling period i s considerably l e s s than the recommended r a t i o of 100 p a r t s BOD t o 1 par t phosphorus. phosphorus, the average concentration of the inf luent increased t o l5 . lppm and the data show a corresponding increase i n BOD removal.

The phosphorus content of 5.9 ppm during the f i r s t

With the addition of

20

On the bas is of removal, t he r a t i o s of BOD removed t o phosphorus a re similar. For the f i rs t se r i e s , the r a t i o i s 1OO:l.l and f o r the second ser ies , it was 100:1.4. It i s speculated tha t i f t he phosphorus content were increased above 15 ppm, an even grea te r increase i n the BOD removal might be real ized.

Tables V I 1 and V I 1 1 a re a summary of data collec.Led on the performance of the t r i c k l i n g f i l t e r . The summary da ta i s divided in to two pa r t s , the f i rs t col lected when only nitrogen w a s added t o the inf luent and the second p a r t when nitrogen and phosphorus were added.

Phosphorus contents shown i n Tables V I 1 and V I 1 1 were determined on unset t led samples. The r e s u l t s between the inf luent and ef f luent a re similar and do not indicate phosphorus uptake by bac ter ia as the analysis measures the amounts of t o t a l phosphorus i n solut ion as w e l l as i n the bac te r i a l mass.

I n general, the pH of the r in se water was l e s s a lka l ine than expected. This f a c t , combined with the high recycle r a t i o , lowered the p H below optimum leve ls fo r biological treatment and resu l ted i n removing fewer pounds of BOD than ant ic ipated.

Additional ana ly t ica l data on da i ly samples may be found i n the EPA Report on t h i s project . (Reference 6)

CONCLUSIONS

EPA Project No. 12060 HFY demonstrated t h a t the gent le abrasion of rapidly ro ta t ing f l ex ib l e rubber d iscs can remove major portions of softened peels on clingstone peaches and y i e ld a canning peach of s a t i s f ac to ry quali ty. Additional work appears desirable t o e s t ab l i sh the full commercial po ten t i a l fo r t h i s method.

The pro jec t demonstrated t h a t a reduction of almost 9% of f r e sh water requirements was feas ib le as a r e s u l t of the p r i o r removal of pee l and caust ic residues by the ro ta t ing rubber discs. This volume can represent 10% of the t o t a l f r e sh water u t i l i z e d by some peach canneries.

The removal of peach pee l and i t s segregation as a s o l i d waste results i n a decrease i n the pounds per day of organic matter discharged from the cannery i n combination with i t s l i qu id eff luent .

Reduced operating cos ts may result from use of a "dry caustic" peeler through lowering the cos ts of water and the operation and maintenance of pr iva te o r municipal waste treatment f a c i l i t i e s .

The gent le peeling act ion of the ro t a t ing discs appears t o be less abusive t o overripe fruit. i n conventional peelers can damage s o f t f l e sh , thereby reducing overa l l commercial acceptabi l i ty .

High pressure r inse water sprays

6 ) Production limitations on certain aspects of the demonstration equipment indicate that modifications are desirable before full commercial potential can be determined.

7 ) Additional work is needed to fully evaluate the potential for utilizing a high rate trickling filter in treatment of concentrated waste effluents from the peeling of peaches.

22

. ACKNOWIJIDGEMENTS

Del Monte Corporation acknowledges the pilot plant evaluations of dry caustic peeling of tree fruits conducted during 1970 by the National Canners Association Berkeley Laboratory in cooperation with the Western Utilization Research Laboratory of USIlA in Albany, California. early efforts and subsequent consultation during the design and develop- ment phase of commercial equipment contributed substantially to this demonstration project.

These

We are further appreciative of the efforts of personnel fromthe National Canners Association Berkeley Laboratory for their management of the sub- project concerned with determining the potential effectivenesss of using a trickling filter biological system for treating concentrated waste water from peach preparation.

We are also indebted to Mr. Kenneth A. Dostal andMr. Harold W. Thompson in the Pacific Xorthwest Water Laboratory of the Environmental Protection Agency for their guidance and numerous helpful suggestions in all phases of the project.

The following members of the Del Monte Corporation made significant contributions to the design and development of commercial equipment, supervision of production, and the obtaining and reporting of results.

Research Department:

Dr. Charles F. Niven, Jr. (Director of Research) Wayne W. Thornburg Raymond M. Jadarola Robert B. Devore Jack G. Allen Jo Ruth Wright Andrew T. Halton Paul Reiche, Jr. Richard J. Maass Demetrios Papakonstantino

Production Management:

William L. Hole Robert E. Crawford Fred H. Laudenslager Gene R. Zolezzi

Engineering Department:

Walter C. Bergstrom Edward E. Garcia Robert M. Jorgensen Richard W. Fish

Charles D. Wintermantel Robert E. McLees Jack B. Schumate Favio Franceschi

23

REFERENCES

Report on EPA Project No. 12060 FQJ, "Dry Caustic Peeling of Tree F ru i t t o Reduce Liquid Waste Volumes and Strength" by National Canners Association, Berkeley Laboratory. December 1970.

National Canners Association, Berkeley, California, Waste Reduction i n Food Canning Operations, Water Qual i ty Office, EPA 12060 -- 08/70.

National Canners Association, Berkeley, California. . Trickling F i l t e r Treatment of F ru i t Processing Waste Waters, Project Number 12969 EAE, Water Qual i ty Office, EPA, Sept. 1971.

Chipperfield, P.N.J. Performance of P la s t i c F i l t e r Media i n Indus t r i a l and Domestic Waste Treatment, JW€CF 3 1860-1874, 1967.

J e r i s , J. S.

Report on EPA Project No. 12060 HFY "Dry Caustic Peeling of Clingstone Peaches on a Commercial Scale" scheduled fo r publication in 1972.

A Rapid COD Test, Water and Waste Engineering - 4 (5) 89-91, 1967.