Jump to main content or area navigation.

Contact Us

facebook iconLike Us on Facebook 
You are here: EPA Home » DfE » Alternatives Assessments

End - Of - Pipe Treatment

8.1 General

End-of-pipe treatment is, by definition, not pollution prevention. However, it is an important aspect of pollution control and it sometimes competes financially with pollution prevention options when facilities are developing pollution control strategies. To make informed decisions about implementing pollution prevention alternatives that include consideration of all applicable costs and potential savings requires accurate data. Therefore, the topic of waste treatment was included in the PWB survey project so that the true costs of treatment could be examined. The applicable portion of the survey form requested respondents to describe the type of waste treatment system currently in use at their facilities and to provide operating and cost data. These data are summarized and discussed in this section.

8.2 Wastewater Characterization

Data that characterize the respondent's raw wastewater from their PWB processes are presented in Exhibit 8-1. The data indicate that copper and lead are the most abundant of the regulated metals. Copper was reported to be present by all respondents. Copper concentrations in the raw wastewaters ranged from 0.4 mg/l to greater than 100 mg/l. Factors affecting the copper concentration of raw wastewater may include: the effectiveness of rinse water controls (which will determine the level of dilution); whether or not process solutions that have relatively high copper concentrations (e.g., spent acids and micro-etches) are commingled directly with rinse water; the effectiveness of drag-out reduction and recovery; and the presence of upstream recovery/recycle technologies, such as ion exchange and electrowinning.

Influent Characterization
Respondent
ID
Production
(board ft2 per year)
Flow
(gpm)
TDS
(mg/l)
pH
(mg/l)
Cu
(mg/l)
Pb
(mg/l)
Ni
(mg/l)
Ag
(mg/l)
TTO
(mg/l)
36930A nr 40 1200.0 8.0 1.0 0.2 0.2 - 0.5
955099 nr 83 - 2.0 30.0 10.0 5.0 - -
55595 nr 15 60.0 6.0 10.0 4.5 4.0 4.0 -
44486 nr 104 - 4.0 nr - - - -
955703 nr 70 - 9.0 0.4 - - - -
6710 15,000 22 - 5.0 20.0 0.9 - - -
947745 40,000 30 40.0 6.0 30.0 2.0 2.0 2.0 -
44657 42,358 6 - 4.0 7.0 1.0 1.0 - -
29710 57,000 120 - - 4.0 - - - -
502100 60,000 25 40.0 8.0 2.0 - - - -
32482 75,000 2 - 4.0 65.0 - - - -
25503 90,000 9 - 5.0 40.0 - - - -
36930 96,000 nr nr nr nr nr nr nr nr
965874 175,000 20 - 8.0 40.0 - - - -
953880 180,000 30 - 4.0 57.0 1.2 0.1 - 1.0
33089 200,000 9 - 3.0 300.0 20.0 - - -
T3 200,000 20 - 8.0 5.0 1.0 - - 2.0
3470 240,000 nr - 2.0 75.0 5.0 5.0 5.0 -
43841 250,000 55 100.0 6.0 200.0 11.0 3.0 0.5 1.5
279 250,000 nr nr nr nr nr nr nr nr
237900 273,000 73 - 9.0 1.2 0.3 0.2 - -
273701 280,000 10 300.0 3.0 50.0 5.0 5.0 - -
41739 300,000 50 - 4.0 25.0 4.0 1.0 0.1 0.1
959951 320,000 20 - 6.0 5.0 1.0 - - -
42692 360,000 70 - 4.0 17.5 0.3 0.1 0.1 -
358000 500,000 30 350.0 8.0 2.0 - - - -
43694 500,000 20 130.0 6.0 30.0 3.0 3.0 - -
37817 540,000 10 - 8.0 3.0 - - - -
42751 540,000 100 1200.0 3.0 33.0 3.0 7.5 - -
T2 600,000 400 - - 30.0 5.0 2.0 - -
133000 600,000 175 - 3.0 60.0 - - - -
T1 936,000 135 - 2.0 35.0 2.0 4.0 - -
740500 1,800,000 300 - 2.0 85.0 - 0.2 - -
946587 1,900,000 60 - 2.0 40.0 2.0 5.0 - -
3023 2,300,000 100 - 4.0 12.5 7.5 - - -
31838 3,000,000 nr nr nr nr nr nr nr nr
462800 3,750,000 103 - 7.0 0.2 0.1 - - -
107300 5,000,000 250 - 4.0 80.0 - - - -

nr = no response

Exhibit 8-1. Wastewater Characterization Data

Sixty-two (62%) of the facilities that provided raw wastewater data reported the presence of lead. Concentrations of lead ranged from less than 1 mg/l to 20 mg/l. The primary sources of lead in a PWB manufacturing process are drag-out from the tin-lead electroplating and stripping operations. Lead may also be introduced in small quantities from reflow or solder-leveling operations. Respondents not reporting lead in their raw wastewater may remove lead with a recovery/recycle technology (e.g., ion exchange) upstream, or may not perform lead plating (or, therefore, stripping). Also, possibly due to a higher sensitivity to lead discharges than some other metals, more aggressive drag-out reduction and recovery methods may be practiced for lead sources.

Forty-eight percent (48%) of the facilities that provided raw wastewater data reported the presence of nickel. Nickel concentrations ranged from less than 1 mg/l to 7.5 mg/l. The most common source of nickel in the raw wastewater is nickel electroplating or electroless nickel plating, which serve as an undercoat for gold. Another common process is the electrolytic nickel-gold plating of the connector edge ("tab plating") of certain PWBs (e.g., PC expansion cards). Wastewater flows generated from these operations may be small in comparison to copper or tin-lead plating operations and drag-out from typical nickel-gold tab electroplating process baths is generally low. Not all PWBs require tab nickel-gold plating, and few require full nickel-gold (see Exhibit 3-1, Outer-Layer small portion of the board is actually immersed in the bath, thereby limiting dragout. Respondents not reporting nickel in their wastestream may perform little or no nickel plating or aggressively recover nickel dragout.

Sixteen percent (16%) of the facilities that provided raw wastewater data reported the presence of silver. Only one respondent reported silver in concentrations greater than 1 mg/l. Silver is present in the photographic developer and fix solutions (and associated rinses) required to create film images. Silver is also used at some PWB facilities for electroplating, but less commonly than for photographic purposes.

Total toxic organics (TTO) were reported in raw wastewater by 20% of the respondents. The primary sources of toxic organics are solder mask ink solvents and screen cleaners, certain film strippers, phototool cleaners, and tape residue removing solvents.

8.3 Types of Processes/Systems Employed

Exhibit 8-2 summarizes the respondent's wastewater treatment equipment purchase data. The primary purpose of the wastewater treatment systems employed is the removal of dissolved metals. This is accomplished by the respondents through installation of conventional metals precipitation systems,n ion exchange-based metals removal systems, and combined precipitation/ion exchange systems. The most common type is conventional metals precipitation systems, which includes precipitation units followed by either clarifiers or membrane filters for solids separation. Sixty-one percent (61%) of the respondents reported having conventional metals precipitation systems installed. Polishing filters are also commonly employed following precipitation/solids separation. The use of clarifiers is the predominant method for separation of precipitated solids from the wastewater (only 12.1% of the respondents with conventional precipitation technology reported using membrane filters).

Respondent
ID
Installation Type of System Flow
(gpm)
Year
Purchased
Cost
($)
Manufacturer Satisfaction
Rating1
Permit
Exceedance
Yes or No2
3023 Initial System (not in use) 100 1984 250,000 Chemtronics 3 Y
3023 Upgrade 1 ion exchange 40 1992 553,000 Memtek 4 -
3023 Upgrade 2 precipitation/membrane 54 1994 125,000 Memtek 4 -
3023 Upgrade 3 resist strip treatment - 1995 60,000 JCL Associates 4 -
3470 Initial System ion exchange 0.5 1993 25,000 none 3 Y
6710 Initial System precipitation/clarifier 22 1987 50,000 JWI 4 N
25503 Initial System ion exchange 9 1991 45,000 Remco 4 N
29710 Initial System unknown 120 nr nr Baker Bros 4 Y
29710 Upgrade 1 ion exchange-copper 12 1991 70,000 Bio Recovery 5 -
29710 Upgrade 2 ion exchange-nickel 3 1992 46,000 Bio Recovery 5 -
29710 Upgrade 3 ion exchange-copper 50 1993 237,000 Kinetco 4 -
32482 Initial System precipitation/clarifier 2 1986 120,000 Lancy 4 N
33089 Initial System precipitation/clarifier 9 1987 4,000 various 2 Y
33089 Upgrade 1 filter press - 1989 12,000 JWI 4 -
33089 Upgrade 2 new tanks, repipe - 1994 6,000 various 5 -
37817 Initial System ion exchange 10 1989 50,000 Eastern Ind Wtr 3 N
37817 Upgrade 1 electrowinning - 1989 6,000 Retec 4 -
41739 Initial System precipitation/membrane 50 1989 300,000 Memtek 4 Y
41739 Upgrade 1 pre/post-treat upgrade - 1993 250,000 Gabel Contracting 5 -
42692 Initial System ion exchange 70 1987 250,000 NCA 3 N
42751 Initial System precipitation/clarifier 100 1986 nr Napco 4 N
42751 Upgrade 1 polishing filter - 1994 16,000 Conrec 3 -
42751 Upgrade 2 filter press - 1994 24,000 JWI 4 -
43694 Initial System ion exchange 20 1990 60,000 Remco 4 N
43841 Initial System precipitation/filtration 55 1983 65,000 DMP 1 Y
43841 Upgrade 1 filter press - 1985 13,000 JWI 5 -
43841 Upgrade 2 equalization pit - 1991 400,000 Generic 3 -
43841 Upgrade 3 filter bags - 1993 1,000 Generic 3 -
44486 Initial System precipitation nr 1990 25,000 unknown 5 N
44657 Initial System precipitation/clarifier 6 1986 200,000 Andco 3 N
55595 Initial System precipitation/filter press 15 1976 1,200,000 in-house 4 N
107300 Initial System precipitation/clarifier 250 1980 nr Durion/Chemtronics 5 N
107300 Upgrade 1 sludge dryer - 1992 83,000 Fenton 3 -
107300 Upgrade 2 equalization tank - 1993 43,000 Fedco 5 -
Exhibit 8-2. Wastewater Treatment Equipment Data

Thirty-three percent (33%) of the respondents reported using ion exchange as their basic waste treatment technology and another 6.1% used ion exchange in conjunction with conventional metals precipitation units. Thirty-six percent (36%) of the ion exchange systems included electrowinning. The use of ion exchange as a waste treatment technology is more widespread in the PWB industry than in the plating industry where it is found in approximately 6% of plating shops (ref. 1). One reason ion exchange is more common as an end-of-pipe technology for PWB shops is the limited number of regulated ionic species present in PWB wastewater. For most shops, copper, lead, and nickel (see Section 8.2) are the only metal ions present in significant concentrations, all of which are amenable to ion exchange. Furthermore, these metals are also easily electrowinned from ion exchange regeneration solutions, which makes the ion exchange/electrowinning combination an effective metal recovery system for PWB shops. Shops using ion exchange tend to be small- to medium-size with the median sales level being $7.5 million, compared to $14.5 million for all respondents.

Column 8 of Exhibit 8-2 shows the satisfaction ratings given by the respondents for their treatment system or system component. The ratings are based on a scale of 1 to 5, with 1 being a low level of satisfaction and 5 being a high level of satisfaction.

Column 9 of Exhibit 8-2 indicates if the respondent reported that a failure, malfunction, or other event associated with the end-of-pipe system resulted in a permit exceedance. Thirty-two percent (32%) of the respondents indicated that they did experience a permit exceedance due to their system. Some respondents reported the nature of the permit exceedance, these included: pH (7.9% of all respondents), Pb (10.5% of all respondents), Cu (10.5% of all respondents), and Ag (2.6% of all respondents).

8.4 End-of-Pipe Treatment Capital Costs

End-of-pipe wastewater treatment capital costs are included in Exhibit 8-2. Capital costs ranged from $1& 1980 for a flow of 135 gpm) to $4,000 (purchased in 1987 for a 9 gpm flow). For ion exchange systems, costs ranged from $250,000 (purchased in 1987 for a 70 gpm flow) to $40,000 (purchased in 1994 for a gpm flow).

8.5 End-of-Pipe Treatment Operation Costs

Exhibit 8-3 displays the major operating costs associated with end-of-pipe wastewater treatment. For the three largest shops (in terms of sales) that provided data, these costs represent 0.29%, 0.37% and 0.35% of sales. The data indicate that waste treatment operating costs, as a percentage of annual sales, are higher for small shops than for large shops. Fourteen percent (14%) of the shops reporting had costs in excess of 2% of sales with the highest being 3.1%. All of these shops had sales near or below the median sales level for all respondents. The median cost for waste treatment as a percentage of annual sales was 0.83%, and the average was 1.02%. A plot of waste treatment operating costs as a percentage of sales volume for all respondents is presented is Exhibit 8-4.

Respondent
ID
Production
(board ft2 per year)
Average Wastewater
Flow
(gpd)
Chemical
Costs
($/yr)
Chemical Costs
($/Kgal of Flow)
Sludge Costs
($/yr)
Routine
O&M
(hrs/yr)
Repair
Time
(hrs/yr)
Costs
($/Kgal of Flow)
36930A nr 27,000 1,600 0.23 0 100 40 0.53
955099 nr 120,000 141,000 4.52 50,000 20,000 300 15.88
55595 nr 20,000 nr - nr nr nr -
44486 nr 100,000 nr - nr nr nr -
955703 nr 98,000 15,500 0.61 nr 7,000 30 4.75
6710 15,000 10,560 6,768 2.47 25,000 1,040 30 17.42
947745 40,000 13,000 13,212 3.91 1,875 780 50 8.15
44657 42,358 6,000 6,460 4.14 3,000 550 30 11.64
29710 57,000 74,000 37,444 1.95 nr 3,552 nr 4.72
502100 60,000 nr nr - nr 1,200 100 -
32482 75,000 31,000 40,492 5.02 4,000 2,200 100 9.80
25503 90,000 5,000 2,200 1.69 720 2,200 40 28.09
36930 96,000 nr 13,100 - nr 800 50 -
965874 175,000 21,000 10,456 1.92 nr 10,000 100 29.66
953880 180,000 35,000 96,092 10.56 48,000 1,760 100 18.90
T3 200,000 16,000 24,185 5.81 20,000 600 240 13.65
33089 200,000 20,000 13,320 2.56 48,000 2,000 100 17.85
3470 240,000 20,000 4,755 0.91 0 2,000 200 7.26
43841 250,000 38,000 26,674 2.70 7,800 5,100 100 11.38
279 250,000 5,200 nr - nr nr nr -
237900 273,000 105,000 87,012 3.19 nr 6,000 425 6.72
273701 280,000 25,000 11,800 1.82 200 3,500 700 11.54
41739 300,000 57,125 71,374 4.81 6,000 3,120 100 8.46
959951 320,000 20,000 48,561 9.32 nr nr nr -
42692 360,000 100,000 172,429 6.63 85,000 4,992 100 12.84
43694 500,000 9,000 20,320 8.68 nr 4,000 40 34.58
358000 500,000 30,000 20,624 2.64 nr 2,500 250 7.93
42751 540,000 6,000 nr - 39,375 10,000 2,500 -
37817 540,000 140,000 6,320 0.17 1,500 550 45 0.46
T2 600,000 48,000 96,250 7.71 nr 3,000 250 11.62
133000 600,000 160,000 167,000 4.01 27,000 6,500 500 7.19
T1 936,000 160,000 167,764 4.03 35,000 2,080 500 5.80
740500 1,800,000 400,000 98,000 0.94 275,000 nr nr 3.59
946587 1,900,000 200,000 108,840 2.09 63,150 8,050 208 5.69
3023 2,300,000 145,000 124,029 3.29 68,000 6,834 342 7.95
31838 3,000,000 280,000 nr - nr nr nr -
462800 3,750,000 26,000 23,875 3.53 0 4,000 150 12.74
107300 5,000,000 250,000 143,850 2.21 60,000 9,275 1,571 5.64
Median:
Mean:
3.24
5.00
9.13
11.41

nr = no response

Exhibit 8-3. Wastewater Treatment Operating Costs

Exhibit 8-4. Waste Treatment System Operational Costs as a Percentage of Annual Sales

8.6 Sludge Generation and Disposal

Wastewater treatment sludge data were presented previously (Exhibit 7-2) and discussed in Sectio (in terms of production) that provided data generated sludge solids at a rate of 0.048, 0.003 and 0.057 lb/ft2 of production. The variation evidently comes, in part, from product mix. The shop generating only 0.003 lb/ft2 is exclusively a single-sided PWB manufacture, whereas the other two have a product mix of double-sided and multilayer PWBs for which additional process steps increase waste generation, including sludge production.

Eighty-eight percent (88%) of those responding indicated they recycle their wastewater treatment sludge. Costs associated with the disposition of sludge ranged from $2.00/lb to $0.13/lb Annual costs and unit costs are given in Exhibit 7-2.

8.7 Air Pollution Control

Exactly one-half of the respondents to this survey have installed air scrubbers (Exhibit 8-5). The processes listed most frequently as requiring scrubbers were ammoniacal etching, HASL (hot air solder leveling), and wet processes in general.

Respondent
ID
Production
(board ft2 per year)
Is Air
Scrubber Installed
Processes or
Chemicals Requiring
Air Scrubber
36930A nr no -
955099 nr yes HASL,microetching,plating
55595 nr yes plating,chemical processing,solder,screening,coati
44486 nr no -
955703 nr yes ammonical etchant
6710 15,000 no -
947745 40,000 no -
44657 42,358 yes hot air level
29710 57,000 yes caustic hot baths, formaldehyde,ammonia from etching
502100 60,000 no -
32482 75,000 no -
25503 90,000 yes cupric chloride etch, copper plating
36930 96,000 no -
965874 175,000 yes plating
953880 180,000 no -
T3 200,000 no -
33089 200,000 no -
3470 240,000 no -
43841 250,000 yes ammoniacal etcher
279 250,000 yes -
237900 273,000 no -
273701 280,000 yes etching, acid vapors, metal roof rust
41739 300,000 yes acids bases and associated wet process chemistries
959951 320,000 yes etching, stripping, plating, formaldehyde
42692 360,000 no -
43694 500,000 yes wet processes areas
358000 500,000 no -
42751 540,000 no -
37817 540,000 no -
T2 600,000 yes -
133000 600,000 yes plating, etching, electroless, gold plate, solder strip
T1 936,000 yes all
740500 1,800,000 no -
946587 1,900,000 yes etch, hydrochloric, sulfuric, nitric acids
3023 2,300,000 yes etch, permanganate, microetch, plating
31838 3,000,000 no -
462800 3,750,000 no -
107300 5,000,000 yes ammonical etch

nr = no response


Exhibit 8-5. Air Pollution Control Devices


IPCExit Disclaimer

Jump to main content.