HEAVY METALS REMOVAL WITH THE DU PONT/OBERLIN MICROFILTRATION TECHNOLOGY

Dr. Ernest Mayer E. 1. du Pont de Nemours, Inc.

P. 0. Box 6090 Newark, DE 19714

Engineering Department Louviers 1

(302) 366-3652

Tyvek' T-980 Media

Du Pont has commercialized a new filter media based on flash spinning technology for Tyvek spunbonded olefin. It has'an 'asymmetric pore structure, a greater number of submicron pores, and a smaller average pore size (1). As a consequence, it has superior filtration properties and longer life, and in many instances it can compete with microporous membranes, PTFE laminates, and various melt-blown media (1). Its key property is its tight pore structure at a very low cost compared to competitive products. Table I outlines the media cost per gallon of waste filtered and shows that the T-980 grade, hich is the lowest basis weight manufactured (0.9 oz/yd*) and the only grade e ated here, is very cost effective. In most applications the T-980 grade was sufficient so the added cost for a higher basis weight grade was not warranted. For example, T-980 produced slightly poorer effluent quality than the 'standard' 0 .45~ microporous membrane at a fraction of the cost; equivalent effluent quality to the PTFE laminate at a fraction of the cost; and much better effluent quality than typical 1- and 5- micron melt-blowns at equal or significantly lower cost (depending on ). Tests with actual wastes showed the greatest cost benefit (Table lar cost benefit was obtained in operation with a low-level radioactiv ste at the Savannah River Plant (2, 3). This installation realized almost annual savings when T-980 media was used with a more efficient filte added benefit is its superior strength compared to microporous membranes and the PTFE laminate media. This strength permits its use in robust automatic pressure filters (4). The high strength (5) coupled with the tight , -1- micron pore structure (1) led to its use in the EPA Superfund SITE program (6-9).

Oberlin Automatic Pressure Filter (APF) **

T-980 media requires a suitable filter housing. The Oberlin Filter Company's automatic pressure filter (APF) was chosen for its simplicity and fully automatic operation (10). Their APF has other advantages, namely:

Completely automatic, unattended operation save for disposable media roll replacement and chemical treatment makeup.

Du Pont's trademark for its flashspun HDPE nonwoven filtration ** Oberlin's name for their automatic pressure filter.

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185

e

e

e

0

e

0

e

0

a

e

e

e

e

Enclosed operation for safety and handling of hazardous wastes.

Fairly high operating pressure (up to 60 psig).

Complete in-line treatment-chemical addition, ie, fitter aids and polymer f locculants.

Automated shutdown flushing capability.

Cake washing capability to remove hazardous filtrate, i f required.

Automatic, positive dry cake discharge.

Direct submicron filtration without the need for further downstream processing.

Reliable, low-maintenance performance.

Completely automatic safety interlocks and enclosures and/or purging, if required.

Explosion-proof design, if required.

Completely integrated pumping system(s), if required.

Dirty-media takeup and doctoring, brushing, or washing, i f required (automatically accomplished during takeup); and, optional media reuse if desired.

Standard PLC control.

Du Pont TyveWOberlin Microfiltration Technology

Thus, the Du Pont TyveWOberlin Microfiltration technology has some unique advantages, especially its completely automatic submicron, low-cost filtration a its dry cake discharge (6). This dry cake discharge feature is precisely why the resultant cakes pass the modified EPA "Paint Filter Test" for land disposal (1 1) and in some instances pass the new EPA TCLP (Toxic Characteristic Leaching Procedure) test for hazardous components (1 2-1 5), provided a stabilization agent is used (i.e., Profix"* was used in the SITE program-9). Dry cakekubmicron filtration in one operation is why the Microfiltration technology was selected at Savannah River over conventional crossflow microfilters and ulttafilters. In plating- waste treatment the simple, one-step Microfiltration technology replaced the be*

Enviroguard's trademark for its patented filter aidktabiliiation agent

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,

conventional t h ree-step clarifie r/ove rflo w sand fi IWunderflow recessed fitter press process. However, the purpose of this paper is to highlight case histories where the Microfittration technology has been successfully applied. The technology is most suitable for hazardous wastewater where the solids loading is not too high (i.e., generally less than about 5000 ppm). Examples include contaminated groundwater, plating wastewaters, low-level radioactive wastes, plant equip- mentlfloor washings, cyanidic wastes, plant wastewaters that contain heavy metals, and metal grinding wastes (2, 3, 81 6). In most of these cases Profix was used per the SITE technology (9) to accomplish automatic, submicron, low-cost microfiltration & stabilization all in one simple operation.

Case Histories

Many successful case histories have been presented previously (2), but a few are worth repeating here, especially those involving heavy metals removal and stabilization. Other new applications are also presented.

Savannah River ODeration

Table I I details actual Savannah River plant wastewater treatment specifically aimed at aluminum and uranium removal (3). The data were obtained from two T- 980/0berlin units which had been operating for about four years. Aluminum forming and metal finishing operations generate a high content of solids, aluminum, and turbidity. These solids can be reduced below the National Pollution Discharge Elimination System (NPDES) limits with the Microfittration technology at very high 1200 gfd (gallons/sq ft/day) rates (1 6). This rate is about six times higher than the ultrafilter (UF)/reverse osmosis (RO) system (200 gfd) originally considered. Pilot testing also showed that the UF/RO system repeatedly fouled with this waste, requiring aggressive cleaning agents which significantly added to the waste volume. Plans are now underway to evaluate Profix in this operation.

'

Electronics Manufacturina Plant Wastewater

This plant's effluent exceeded the local sewer authority's lead discharge limit. As a Consequence, the plant was mandated to cease discharge and dispose of their wastewater in an off-site hazardous waste landfill at a $0.55/gallon cost. Two Microfiltration systems were installed instead of crossflow microfilters because their dry cake feature significantly reduced waste volume. These units repaid their cost in three months of operation based on disposal cost savings alone (16).

Table 111 details actual plant operation and compares the Microfittration effluent with the plant's discharge limits. As shown, these units reduced the effluent Total Suspended Solids (TSS) and lead levels to well below the plant's required discharge limits at high 800 gfd flux rates. In addition, these units routinely achieved >50% solids dry cakes that could be disposed of in a RCRA-approved landfill (at significant cost savings compared to the concentrate from the crossflow

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microfilters). Subsequent evaluation of the Profix filter aid/stabilization agent per the SITE technology (9) actually improved flux and resulted in stabilized cakes (passed TCLP).

Electronics Plant Cartridge Replacement

This plant's effluent had to be polished by absolute 0.45-micron cartridge filters to meet heavy-metal discharge limits. Cartridge costs exceeded $1 200 daily plus significant labor charges (1 6). A Microfittration system was installed at significant cost savings compared to these cartridges or a crossflow microfilter which was also considered. Payback was on the order of three months; the system produced dry cakes suitable for landfilling off-site, and significant labor savings resulted.

Table IV demonstrates that the Microfiltration system easily met the TSS and lead discharge limits at very high 1500 gfd flux. Cakes were also quite dry at -50% solids.

Clarifier Underflow Heavy Metals Removal

This plant was faced with a land ban of their main clarifier metal hydroxide underflow sludge (2-3% solids) because it did not pass the EPA "Paint Filter Test" (1 1). This clarifier treated the entire plant effluent and removed primarily lead, zinc, and copper. To satisfy the RCRA land ban restrictions, the plant hired an expensive ($4OO/day) mobile dewaterer who used a manual, recessed-chamber filter press that produced sloppy cakes. These cakes had to be shovelled into dumpsters for off-site disposal. The Microfiltration technology was installed about two years ago. Table V shows excellent effluent quality at very high, 10,000 gpd capacity and 900 gfd flux. The cakes were sufficiently dry (50% solids vs. 40% requirement) to pass the "Paint Filter Test" and were acceptable to the hauler/landfiII operator at a significant cost saving to the plant. The Microfittration system operates automatically at significant labor savings compared to the manual press. Profix has been evaluated here and will be implemented in the next few months since the resultant cakes pass TCLP particularly for lead (Table V).

Battery Manufacturing Heavy Metals Removal

This plant consistently exceeded their permitted discharge limits from their con- ventional clarifier/underflow press system and considered an overflow polishing sand filter. Simultaneously, they heard of our Microfiltration technology and decided to evaluate it as a polishing filter. Testing showed that it could replace the entire clarifier/press installation. Table VI shows excellent metals removal, TSS reduction, and excellent effluent turbidity (0.5 NTU). Flux is quite high at 2400 gfd and capacity from the single system exceeds 60,000 gpd. These benefits are in addition to dry cakes that could be easily disposed of in a RCRA-approved landfill.

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h z t Yeavy Metals Removal from Chemical Plant Wastewater

This plant was faced with severe heavy metal discharge restrictions based on recent EPA chronic toxicity regulations (ie, 15 ppb Cu, 60 ppb Pb, 130 ppb Ni, 150 ppb Cr, and 300 ppb Zn). In addition, this mixed heavy metals waste had to be stabilized to meet the "third-third" EPA BDAT (Best Demonstrated Available Technology) regulations for land disposal (2, 12, & 13). Ion exchange was first evaluated, but it could not meet the low ppb limits for all the metals and its regenerant required off-site stabilization at high cost. As a result, the Microfiltration technology was next evaluated since it could produce dry, stabilized cakes, but previously it never achieved these low metals limits. An extensive pilot testing program was conducted and finally, it was demonstrated that these limits could be achieved quite routinely (Table VII). In addition, these low metals limits were obtained at a very high 3600 gfd flux; and the resultant "dry" cakes passed the TCLP test for all eight toxic metals (per EPA "third-third" regulations issued May 8, 1990 - Refs. 12 & 13). As a consequence, the Microfiltration technology was selected and three large systems are being installed along with a Profix addition system.

.

Groundwater Lead Removal

A RCRA hazardous site required lead removal from contaminated groundwater to a level of less than 50 ppb to meet primary drinking water standards as well as the chronic toxicity criteria. The responsible party hired an outside consulting firm to

. study and recommend a suitable treatment scheme. Unfortunately, their piloted treatment process could only achieve 4 ppm; and their recommended activated carbon polishing step also could not achieve the low required 50 ppb lead discharge limit. The Microfiltration technology was then evaluated and outstanding 4 0 ppb lead removals were obtained (Table VIII). As a result, this technology will be used and a single large system is being installed. Profix was used here and the cakes passed TCLP for lead.

Chemical Plant's Groundwater Metals Removal

This plant had groundwater contaminated with metals and organics, and hired an outside consulting firm to study and recommend a suitable treatment scheme. Unfortunately, their piloted sand filter scheme couldn't achieve the required low metals levels; and as a result the Microfittration technology was evaluated. As can be seen from Table IX, it achieved outstanding metals removal (Le., below detection limits) at a very high 4000 gfd flux. In addition, filtrate turbidity, TSS, and cake % solids were all excellent; and the cakes passed TCLP. As a result, the system is now being installed to treat this groundwater.

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i Groundwater Hexavalent Chrome Removal

This Superfund site required groundwater chrome removal to the 50 ppb level. Simple sodium bisulfite chrome reduction followed by Microfittration resulted in excellent chrome removal to below the 50 ppb detection limit, as well as excellent filtrate TSS and turbidity (Table X). Flux was very high at 3600 gfd and the resultant cakes were stabilized. However, the client opted for ion exchange (IX) since only one metal was present and it reduced solid waste volume. In this case, IX was a better choice for the client; and illustrates that all metals removal technologies have their niche.

Groundwater Mixed Metals Removal

This mixed organicslmetals contaminated groundwater was chemically treated to destroy the toxic organics and the resultant effluent was treated by the Microfiltration technology (Table XI). As can be seen from Table XI, excellent metals removals were obtained basically to the detection limits. Flux was reasonable (1750 gfd) considering the high 50 ppm Fe content; cakes passed the new TCLP test; and filtrate turbidity and TSS were outstanding at 0.05 NTU and 0.03 ppm, respectively (Le., better than distilled water). Consequently, a Microfittration system has been purchased.

Wastewater Mixed Metals Removal

This plant required stringent heavy metals removal to meet chronic aquatic toxicity criteria. A variety of technologies were evaluated, but the Microfiltration technology provided the best overall metals removal of this waste (Table XII) as most were removed to below detection limits. The resultant cakes also passed TCLP, which was also a big factor since other technologies required additional post-treatment to produce stabilized solids.

Wastewater Zinc Removal

This wastewater required zinc removal to 1 ppm prior to discharge; and in this case, only the Microfiltration technology was evaluated because selective ion exchange could not achieve the 1 ppm limit. Table Xlll shows that the Microfittration system easily achieved the 1 ppm Zn limit as well as excellent Cd, Pb, and Cu removals like in the SITE demonstration (9) where these metals are normally associated with Zn smelting. In addition, filtrate turbidity and TSS were excellent and flux was reasonably high (1000 gfd) for this high 3000 ppm TSS waste. Cakes again passed the TCLP test. In this case, despite the promising microfiltration results the plant opted to incinerate this waste.

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Actual EPA Site Demonstration

The Du Pont/Oberlin microfiltration technology was demonstrated by the EPA under the SITE program in April - May, 1990 at the Palmerton, PA Superfund site (7, 8, 9, & 16). This site's groundwater is contaminated with heavy metals by runoff from a huge 2.5 mile long cinder bank as a resutt of a zinc smelting operation. As expected, the groundwater contained high concentrations of zinc as well as manganese, lead, cadmium, copper and selenium (Table XIV). The Microfikration system was able to remove 99.95% of the zinc, 99.95% of the TSS, produce dry cakes that passed the "Paint Fitter Liquids Test", 41% cake solids, fittrate that met NPDES discharge limits, and cakes that passed both the EP Toxicity and the new TCLP test, because the new filter aid / stabilization agent (Profix) was used (7 ,8, 9, & 16).

Summary

These cases and actual operating applications demonstrate the uttlity of the Du Pont /Oberlin microfiltration technology to remove heavy metals at very high flux rates a to simultaneously produce dry cakes that pass the EPA "Paint Fitter Test", and in some cases, the new EPA TCLP leaching test (if Profix filter aid/stabilization agent is used per SITE demonstration C. Refs. 2, 6, 7, 9). This technology is quite competitive when compared to microfilter cartridges, crossflow microfilters, and ultrafilters. In some instances, the system can replace the conventional three-stage metal finishing treatment process of clarifier, underflow filter press, and overflow polishing sand filter. Thus, the waste engineer/consuftant now has a simpler, one-step process for treating and stabilizing hazardous metal- bearing wastewaters and groundwaters.

References

1. Lim, H. S., and Mayer, E., Fluid/Parti& Se- J o W , 2(1), 17-21, (MarchJ989).

2. Mayer, E., Paper presented at US EPA Second Forum on Innovative Hazardous Waste Treatment Technologies", Philadelphia, PA, May 15-1 7, 1990.

3. Martin, H. L., Paper presented at 10th Annual AESF/EPA Conference on Environmental Control for the Metal Finishing Industry, Orlando, FL, January 23-25, 1989.

Mayer, E., Eil&&ism News ,24-27 (May/June, 1988): "New Trends in SLS Dewatering Equipment."

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5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

Du Pont Tyveka Bulletin E-24534, 1988: "Tyvekm Engineered Specifically for Filtration."

Mayer, E., Request for Proposal, SITE-3 Solicitation, Demonstration of Alternative and/or Innovative Technologies, "Groundwater Remediation Via Low-Cost Microfiltration for Removal of Heavy Metals and Suspended Solids," February, 1988.

Topudurti, K., Labunski, S., and Martin, J., Proceedings of 11 th National Conference, Superfund '90, Washington, DC, November 26-28, 1990.

Stacy, G. L., and James, S. C. , Dntrol H m ' , VOI. 4(1), 23- 26,43-46 (JanJFeb., 1991).

EPA Final Technology Evaluation Report: "SITE Program Demonstration of the Du PonVObertin Microfiltration Technology", July 1991.

Oberlin Filter Co.'s Bulletin, February, 1988: "Oberlin Pressure Fitter."

Snell, N. J., Pollution Ena, 44-49 (August, 1988).

Federal Register, Vol. 51, No. 114 (June 13, 1986); and updates: Vol. 53, No. 159 (August 17,1988) and Vol. 55, No. 61 (March 29, 1990).

Newton, J., epUlJtion Eno, , =(9), 90-98 (September, 1990).

Biedry, J., -on m, =(lo), 46-49 (October, 1990).

Hauck, J., and Masoomian, S., -, a(5) , 81 -84 (May, 1990).

EPA Final Applications Analysis Report: "Du PonVOberlin Microfittration Technology", May, 1991.

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MEDIA

Nom. Overall Rating Filtrate

Media (pm) Quality

0.45 Excellent 29 69 14

1 V. Good 1 3 1.7 0.3

Microporous Membrane

Tyvek@ T-980

PTFE Laminate 0.8 V. Good 41 63 12

Melt-blown PP 1 Good 2.4 6.5 1 3

Melt-blown PP

Based on actual media costs, flux rates, and m AC Fine Test Dust (ACFTD) challenge tests. **

Turbidity (NTU) 110 0.32

687

127

1.6

0.5

2.0

1.4

0.95

0.2

< 0.1

< 0.1 ~

2.3 0.01 .

35,000 60,000

31

3 2

0.43 -

0.32

0.21

0.5

- 1,200 - Flux (gfd)

Actual State discharge permit values.

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ImEJu ACTUAL ELECTRONICS MANUFACTURING PLANT WASTEWATER

Raw Du PonV Discharge Property Waste' Oberlin Limits

Turbidity (NTU) >1,000 0.3 NR

Lead (ppm)

Barium(ppm) ' '

Cadmium (ppm)

Capacity (gpd)

Flux (gfd)

Cake % Solids

Cakes Pass TCLP?

20

25

0.04

<le*

2 <0.05"

2,500 4,500

-- 800

-- 54

No Yes

1 .o NR

NR --

---

Must pass

JAE&ElY ELECTRONICS PLANT CARTRIDGE FILTER REPLACEMENT

Raw Property Waste'

Turbidity (NTU) 2,400

5,500

2,300

Flux (gfd) --- Cake % Solids -I

Du PonV Oberlin

0.43

1 .o 0.1 8

1 1,000

1,500

50

Discharge Limits

NR

20

0.7

c

** Includes floor washings also. Detection Umit

NR = Not Regulated.

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! I4U.u CLARIFIER UNDERFLOW HEAVY METALS. REMOVAL

, '

Raw Du PonV Discharge Property Waste' Oberiin Umits

Turbidity (NTU) >1,000 1 .o NFI

TSS (PPm) 17,000 2.5 20

Lead (ppm) 40 <0.01" 5.0

Zinc (ppm) 41 0 0.2 5.0

Copper (PPm) 1,050 1.2 5.0 6,800 10,000 -- Capacity (gpd)

Flux (gfd) -- 900 -- Cake % Solids --- 5 0 . 40

Cakes Pass TCLP? No Yes Must pass

I"EA DIRECT FILTRATION FOR HEAVY METALS REMOVAL

FROM A BAlTERY MANUFACTURING PLANT

ProDettv Raw

Waste

Turbidity (NTU)

TSS (PPm) Nickel (ppm)

Cadmium (ppm)

Zinc (ppm)

Cobalt (ppm)

Capacity (gpd)

Flux (gfd)

175

1,600 30-50

15-40

0.2-1 .o 0.4-1.5

40,000

Du PonV Oberlin

0.5

<1 <0.10

<0.05

<O.lO

<0.05

60,000

2,400

Discharge Limits

M

20

2.27 0.4

1.68

0.22

~

' Existing plant clarifier underflow sludge was previously hauled off-site to hazqrdous landfill. Detectionlimit Replaced clarifier and underflow press. .H

NR = Not Regulated.

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HEAVY METALS REMOVAL FROM CHEMICAL PLANT WASTEWATER -

Raw Du Pont Discharge Property Waste Oberlin Limits"

Turbidity (NTU)

TSS (wm) Copper (PPb)

Lead (PPW

Zinc (PPW Nickel (ppb)

Chromium (ppb)

Capacity (gpd)

Flux (gfd)

Cakes Pass TCLP?

>loo 100

2,000

100

3,500

400

1,000

75,000

No

0.06

<0.2

d

<5 *

< lo <5

< loo* 130,000

3,600

Yes

<o .2 <1

15

60

250 130 150

--- -e-

Must Pass

GROUNDWATER LEAD REMOVAL

Raw Du PonV Discharge Property Groundwater Oberlin Limits **

Turbidity (NTU) s10 0.1 NR

-- 1,400 Flux (gfd) - Cakes Pass TCLP? No Yes Must Pass

c

** Detection limits. Based on EPA Chronic Toxicity tests

NR = Not Regulated

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CHEMICAL PLANT GROUNdWATER METALS REMOVAL .- . .. -

Raw Du Pontl Discharge Property Groundwater Oberlin Limits **

Turbidity (NTU) 100 0.1 , NR

Fe (PPm) 40 4.1 NR

Ba (PPW 900 500 NR Cr (PPW 45 <lo* 150

Ni (PPb) 50 <5' 130

zn (Ppb) 300 <lo* 250

cake % Solids -- 56 -- 4000 --

Cakes Pass TCLP? No Yes Must Pass

TSS (PPm) 80 0 3 20

-- Flux (gfd)

ImJEx GROUNDWATER CHROME REMOVAL FROM SUPERFUND - 1 SITE

Raw Du PonV Discharge Property Groundwater Oberlin Limits **

Turbidity (NTU) 30 0.07 NR TSS (wm) 40 0.3 NR

Cr (PPm)

Cake YO Solids --- 56

Flux, (gfd) Cakes Pat% TCLP? No Yes Must Pass

3-1 2 ~0.05' 0.05 (hexavalent)

-- -- 3600 --

Detection Umit ** Based on EPA chronic toxicity standards NR- Not Regulated

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IABLuu GROUNDWATER METALS REMOVAL

Raw Du Pontl Discharge Property Groundwater Oberlin Limits ''

Turbidity (NTU) 160 0.05 NR

TSS (wm) 180 0.03 30

Fe (PPb) 50,000 <loo* NR

Cr (PPW 40 10 150

Ni (PPW 300 <5' 130 @Pb) 14,000 <lo' 300

-- 1750 --- Flux (gfd) Cakes Pass TCLP? No Yes Must Pass

I2wLU MIXED WASTEWATER METALS REMOVAL

Raw Du Pontl Discharge Property Groundwater Oberlin Limits "

Turbidity (NTU) 4000 02 NR TSS (wm) 1200 0.4 20

Fe (wm) 80 4.1' NR

Cr (PPb) 1800 50 150

cu (PPb) 1000 4' 15

Zn @Pb) 14,000 40' 250 Cake % Solids -- Flux (gfd) -- Cakes Pass TCLP? No

--- 51 400 --- Yes Must Pass

* Detection limit *' Based on EPA Chronic Toxicity Tests. NR- Not Regulated

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- WASTEWATER ZINC REMOVAL

Raw Du Pont/ Discharge Property Wastewater Oberlin Limits

Turbidity (NTU) >loo0 0.2

TSS (P" 3000 20

Zinc (ppm) 1500 1

Pb (wm) 0.70 d.005' NR

Flux (gfd) -- 1 00 -

(PPW . 0.15 eO.01' NR

cu (PPm) 0.25 d.005' NR

Cake Pass TCLP? No Yes Must Pass

"LUY DU PONTIOBERLJN MICROFILTRATION TECHNOLOGY DEMONSTRATION

BY EPA AT PALMERTON, PA SUPERFUND SITE

Property Waste Oberlin Limits" Raw Du PonV Discharge

Turbidity (NTU) > 1,000 0.1 NR

TSS (wm) 1,700 0.8 30

Zinc (ppm) 500 0.25 2.4

Manganese (ppm) 50 <0.1 ' NR

Lead (ppm) 0.1 0.025 0.7 .

Cadmium (ppm) 0.5 0.005 0.2

Copper (PPm) 0.2 0.003 NR

Selenium (ppm) 0.1 0.040 NR

Cake % Solids -- >40 NR Cakes Pass EP Tox? No ' Yes NR Cakes Pass TCLP? No Yes Must Pass

4 4 Detection Limit. NPDES discharge limits.

NR= Not Regulated.

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