William L. Payne
Westinghouse Savannah River Company
Aiken, SC 29808

The Savannah River Site (SRS) often generates wastewater for disposal that is not included as a source to one of the site’s wastewater treatment facilities that are permitted by the South Carolina Department of Health and Environmental Control (SCDHEC). The techniques used by the SRS contract operator (Westinghouse Savannah River Company) to evaluate and treat this unanticipated ‘scavenger’ wastewater may benefit industries and municipalities who experience similar needs.

Regulations require that scavenger wastewater be treated and not just diluted. Each of the pollutants that are present must meet effluent permit limitations and/or receiving stream water quality standards. If a scavenger wastewater is classified as ‘hazardous’ under the Resource Conservation and Recovery Act (RCRA), its disposal must comply with RCRA regulations.

Westinghouse Savannah River Company (WSRC) obtained approval from SCDHEC to dispose of scavenger wastewater under specific conditions that are included within the SRS National Pollutant Discharge Elimination System permit. Scavenger wastewater is analyzed in a laboratory to determine its constituency. Pollutant values are entered into spreadsheets that calculate treatment plant removal capabilities and instream concentrations. Disposal rates are computed, ensuring compliance with regulatory requirements and protection of treatment system operating units. Appropriate records are maintained in the event of an audit.

SRS covers approximately 300 square miles of South Carolina and is located along the Savannah River in southwestern South Carolina (figure 1). It is a Department of Energy (DOE) facility that once manufactured nuclear materials for the United States weapons program. Today, its primary function is the cleanup of nuclear waste and environmental restoration.

Day-to-day operations and environmental cleanup result in the generation of a variety of unanticipated wastewaters that must be disposed in some manner. SRS defines these wastewaters as "scavenger wastewater." Scavenger wastewater is usually comprised of liquid wastes that do not have a method of disposal that is permitted by SCDHEC. In the past, SRS had to obtain DHEC approval to treat each individual scavenger wastewater in site treatment facilities. This was time consuming and difficult and sometimes resulted in the disposal of certain wastewaters as hazardous wastes when less expensive disposal options were available. In 1995, SRS obtained SCDHEC’s approval to make decisions about scavenger wastewater treatment without first obtaining their concurrence. This approval was later written into the SRS NPDES permit as a special condition. Since 1996, approximately 140 scavenger wastewaters have been evaluated, disposed and treated in SRS WWTPs, saving considerable dollars.

Figure 1 – Savannah River Site Location in South Carolina

Although there are several permitted wastewater treatment plants (WWTPs) at SRS, only two are normally used to treat scavenger wastewaters. The Effluent Treatment Facility (ETF) employs physical/chemical treatment that includes filtration, pH adjustment, evaporation, granular activated carbon, reverse osmosis and ion exchange (figure 2). This complex facility was designed primarily to remove radionuclides, heavy metals and organics from specific operational processes. Due to its full array of treatment capabilities, it also works very well for complex scavenger wastewaters. It may not be the WWTP of choice for simpler wastewaters or wastewaters that contain significant amounts of certain organics.

Figure 2 – Effluent Treatment Facility

For scavenger wastewaters containing significant amounts of organics and/or minor amounts of other constituents, the site’s central sanitary wastewater treatment plant (CSWTP) is often employed. The CSWTP primarily treats sanitary sewage by way of extended aeration activated sludge within oxidation ditches (figure 3). Boat clarifiers are located within the oxidation ditches and effluent is disinfected with ultraviolet light. Biosolids are dewatered within drying beds and land applied on pine forests located on SRS property.

Figure 3 – Central Sanitary Wastewater Treatment Plant

SCDHEC issues construction and operating permits for wastewater treatment plants in South Carolina. They also issue NPDES permits for their discharges to surface waters. The scavenger wastewater program allows SRS to dispose of unanticipated wastewaters without having to modify either of these permits. But it does not allow SRS to circumvent the basis behind these permits. All scavenger wastewaters that are disposed within the ETF and the CSWTP are evaluated carefully to ensure that they are treatable and that each pollutant will meet effluent limitations and receiving stream water quality standards (WQS). This requires the generator to know what pollutants are present, which usually requires laboratory analysis – although process knowledge is occasionally adequate. If SRS WWTPs cannot treat a particular pollutant but it would meet stream standards simply by dilution, then the scavenger wastewater is not disposed. Dilution alone is not considered to be a responsible, or legal, method to attain a limit or standard.

It is not unusual for scavenger wastewaters to also be classified as hazardous under the Resource Conservation and Recovery Act (RCRA). RCRA regulations are complex and the disposal of hazardous wastes under the scavenger wastewater program requires careful evaluation to ensure that RCRA requirements are met. All wastewaters that are hazardous require completion of a Land Disposal Restriction (LDR) note to file prior to disposal in a Clean Water Act facility. This is specified in 40 CFR 268.7(a)(7), which states that "if a generator determines that he is managing a prohibited waste that is excluded from the definition of hazardous or solid waste or is exempted from Subtitle C regulation under 40 CFR 261.2 through 261.6 subsequent to the point of generation (including deactivated characteristic hazardous wastewater managed in wastewater treatment systems subject to the Clean Water as specified in 40 CFR 261.4(a)(2) or that are Clean Water Act equivalent), he must place a one-time notice describing such generation, subsequent exclusion from the definition of hazardous or solid waste or exemption from RCRA Subtitle C regulation, and the disposition of the waste, in the facility’s on-site files."

Many hazardous scavenger wastewaters originate from laboratories. As such, it is often possible to claim the laboratory exclusion available in regulations found under 40 CFR 261.3(a)(2)(iv)(E) for wastewaters that are toxic. This exclusion requires that the influent entering the WWTP be less than either one part per million or one percent of the total annual flow to the headworks. A similar exclusion exists for solvents in the same section of the regulation. SRS maintains careful controls to ensure that all requirements are met whenever these exclusions are utilized.

Understanding the source of the scavenger wastewater helps determine what lab analyses need to be obtained prior to determining the best method of disposal. For example, rainwater collected in a sump where nothing more than minor leakage from process related equipment has been received may call for nothing more than an analysis of total carbon, pH, suspended solids and a few heavy metals. On the other hand, disposal of wastewater from a seepage basin that is undergoing remediation under a Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) cleanup may require a full array of organic and inorganic analyses. In any event, it is very important to know exactly what is in the wastewater prior to determining the best location for disposal and treatment. Without this information, it would be easy to accidentally dispose of untreatable pollutants in a particular system and/or incorrectly identify them as RCRA hazardous.

Once accurate laboratory data has been collected, the scavenger wastewater must be evaluated to determine its treatability. It is often difficult to locate literature that provides this information for specific chemicals. For example, determining how well copper is removed in an activated sludge wastewater treatment process might be difficult. Yet, this information is vital in order to ensure compliance with effluent limitations and/or the South Carolina aquatic life WQS of 2.9 micrograms per liter (ug/l). The Environmental Protection Agency (EPA) once maintained a database that provided removal capabilities for many different treatment processes covering hundreds of chemicals. This database, provided by EPA’s Risk Reduction Engineering Laboratory (RREL), continues to be a fairly comprehensive source of information. It can still be located on the Internet, but it requires someone who is Internet savvy. SRS continues to use this database as a primary means of determining treatability. Due to its age, it is a Microsoft Disk Operating System (DOS) program that must be installed on a Microsoft Windows operating system. Although somewhat archaic by today’s standards, performing a search on a particular chemical results in the display of a table showing percent removals at varying influent concentrations for many types of treatment (figure 4).

Another tool that is available for activated sludge treatment systems is the Water Environment Research Foundation’s (WERF) book entitled "Chemical Characteristics and Solids Uptake of Heavy Metals in Wastewater Treatment." This document advances the understanding of the transport and fate of various species of metals, such as zinc and aluminum in the wastewater treatment process. It also includes a computer program based in Microsoft Excel that allows wastewater treatment plants to calculate the fate and transport of heavy metals. Figure 5 provides an example table of results obtained by this database. WERF also has other resources that may be valuable in determining the treatment and removal capabilities of certain wastewater treatment systems.

If literature cannot be located for a particular pollutant or range of pollutants, a treatability study can be undertaken. SRS typically does not perform these studies; however, they can be easily undertaken in the lab operated by the treatment facility. A ten-gallon aquarium can be used as an activated sludge basin, a large funnel as a clarifier, and a small peristaltic pump to move liquid through the system. Although somewhat time consuming, treatability studies may be the best way to determine the removal capabilities for particular chemicals since they are evaluated against activated sludge obtained from the actual WWTP that will treat the wastewater.

Determining whether or not particular pollutants can be removed in a treatment system is only part of the task. The next step is to resolve whether or not instream WQS will be attained after treatment. Looking again at copper, an effluent needs to contain less than 2.9 ug/l to achieve compliance when the receiving stream low flow condition (7Q10) is zero. Since blending with the receiving stream is allowed under South Carolina regulations, the instream dilution factor can be found easily by using the calculation shown below.

The effluent concentration is determined by the following calculation.

Upon determining these two values, the instream pollutant concentration can easily be determined by the following calculation.

The value for C_S can be compared to the WQS to ensure compliance. An additional safety factor may also be utilized, if desired. For example, C_S could be restricted to one-half or even one-tenth of the WQS.

WQSs do not exist for many chemicals. Nevertheless, it is important to ensure that their disposal into the environment will not cause negative effects within receiving streams. To provide this assurance, Whole Effluent Toxicity (WET) tests can be performed directly on scavenger wastewaters, but this option is expensive. A better idea is to obtain existing WET information, where available. EPA maintains an aquatic toxicity database called "ECOTOX" that provides a plethora of information. It can be accessed by anyone using the Internet at www.epa.gov/ECOTOX. The species of choice for performing database searches for toxicity information are daphnids because they are typically the most sensitive species and provide the most conservative results. Figure 6 provides an example table found in the ECOTOX database.

Figure 6 – Example Table Found in EPA’s ECOTOX Database

The most conservative LC50 value (a measure of acute toxicity) from Figure 6 is 280,000 ug/l. The margin of safety factor contained in the SCDHEC water quality standards regulation (R.61-68) must be applied to this value. For LC50 data, that factor is 33, making the derived water quality standard in this example 8,484 ug/l (280,000 divided by 33).

Referring back to the example in figure 5, constituents such as copper bioaccumulate in sludge that is a byproduct of biological treatment. Limitations contained in 40 CFR 503 regulations for the use and disposal of sewage sludge could be exceeded in biological systems. Prior to treatment, a determination should be made regarding whether or not a scavenger wastewater will result in sludge disposal problems. This is usually more problematic when treating metal wastewaters because most organic pollutants biodegrade more readily.

Since the Scavenger Wastewater program is specified in the SRS NPDES permit, complete records of each scavenger wastewater disposal are maintained in the event of an audit by either the regulating authority or the SRS Facility Evaluation Board (FEB) – an internal auditing group. These records help ensure compliance, but they also provide documentation that scavenger wastewater disposals are not responsible for WWTP process upsets, should they occur.

The first case study examines a particular laboratory scavenger wastewater that was evaluated for disposal at the SRS CSWTP. The purpose of the laboratory is to analyze groundwater samples. In so doing, it generates solvent wastewater that is often RCRA hazardous. Constituents such as methylene chloride and pyridine make it a complex wastewater to evaluate. The RREL database was utilized to determine removal rates for each wastewater constituent treated in the CSWTP activated sludge treatment system. The results indicated that each constituent would receive a reasonable level of treatment and that disposal into the CSWTP was appropriate.

A comparison of RREL treatability results against South Carolina WQSs was indeterminate for methylene chloride and pyridine since no aquatic life standards exist for these chemicals. Adding to this problem was the concern that this scavenger wastewater could cause the CSWTP effluent to fail its WET test. Therefore, a sample of the laboratory scavenger wastewater was analyzed for WET to determine both the level of treatment necessary to ensure protection of instream biota and the volume that could be disposed per day into the CSWTP. A dilution series test determined that the No Observed Effect Concentration (NOEC) was established at a dilution factor of 1 to 4,000. After applying SCDHEC’s safety factor of 3.3 for chronic toxicity test results found in Regulation 61-68 and adding an additional safety factor of 2, it was determined that approximately 5.5 gallons per day of this scavenger wastewater could be disposed into the CSWTP and not cause the effluent to fail its WET test. When combined with RREL treatability results, a final disposal volume was established.

Figure 7 provides information about the constituents present in the wastewater, their expected levels of treatment, and a comparison to WQSs. Considering each of these factors as well as WET test results, SRS determined that the 5.5 gallons per day value established by WET testing was appropriate for the CSWTP. Since the laboratory generates only about 3 gallons of wastewater daily, this disposal rate was determined to be adequate.

Analyte	Wastewater Concentration (mg/l)	Removal (%)	Water Quality Standard (mg/l)	Calculated Instream Concentration (mg/l)
pH	5.15	-	6.0 – 8.5	6.0 – 8.5
TSS	466.00	99.9	None	1
Total Organic Carbon	17400.00	99.9	None	17
Acetone	284.00	73	None	0.00005
Methylene chloride	1530.00	70	None	0.000164
Pyridine	14500.00	95	None	0.00026
Toluene	50.00	94	6.8	0.00001
Trichloroethylene	58.40	90	0.0027	0.00002
Arsenic	0.11	37	0.000018	0.00000002
Copper	0.11	81	0.0029	0.00000002
Iron	78.20	82	0.3	0.000009
Nickel	0.15	32	0.016	0.00000007

This laboratory scavenger wastewater was determined to be hazardous waste. As such, it could not be disposed into the CSWTP unless it met the exclusions provided within RCRA regulations. An evaluation against these exclusions determined that this wastewater would easily meet the one-percent requirement contained in 40 CFR 261.3(a)(2)(iv)(E) and that individual solvent constituents met the solvent exclusion. In addition, a one-time notification to file was completed to meet LDR requirements.

The second case study involved the disposal of a relatively benign wastewater generated as a result of closing a WWTP that was no longer needed in one area of SRS. The final 2,000 gallons of wastewater remaining within this particular physical/chemical WWTP required a place for treatment and disposal and the most logical location was determined to be the SRS ETF. The ETF (described above) is also a physical/chemical WWTP and was expected to provide excellent treatment for this scavenger wastewater. Once again, the RREL database was utilized to determine treatability of certain constituents.

On this occasion, no water quality standards were available on two of the pollutants in the wastewater

(4-methyl-2-pentanone and o-nitroaniline) and the cost to perform WET tests to determine appropriate disposal rates would have been unreasonable. Therefore, EPA’s ECOTOX database was accessed to establish appropriate instream standards and ensure protection of the receiving stream. Figure 8 provides results of the evaluation of this scavenger wastewater for disposal into the ETF.

The SRS Scavenger Wastewater Program has been utilized successfully for years. SCDHEC representatives have acknowledged its success by continuing to include it within the SRS NPDES permit rather than reviewing and approving scavenger wastewater disposals themselves. No program is perfect, but the highly technical manner in which scavenger wastewaters are handled at SRS leaves little chance for mistakes that might result in discharges that would harm the environment. Industrial plants and/or publicly owned treatment works (POTWs) can utilize these methods to ensure protection of their own wastewater treatment facilities and associated effluents and receiving streams.

United States Code of Federal Regulations, 40 CFR 268.7(a)(7), http://www.gpoaccess.gov/cfr/index.html.

United States Code of Federal Regulations, 40 CFR 261.3(a)(2)(iv)(E), http://www.gpoaccess.gov/cfr/index.html.

Risk Reduction Engineering Laboratory (RREL) Treatability Database, US-EPA (no longer provided by EPA but may still be located via an internet search).

C. B. Huang et.al, Chemical Characteristics and Solids Uptake of Heavy Metals in Wastewater Treatment, Water Environment Research Foundation, Project #93-CTS-1, (2000).

ECOTOXicology Database (ECOTOX), US-EPA, http://www.epa.gov/ECOTOX.