2/10/97
MWRA/MASCO Hospital Mercury Work Group
End-of-Pipe Subcommittee, Technology Identification Subgroup
SCOPE OF WORK
Feasibility Testing
Objectives
The Technology Identification Subgroup (the Subgroup) has established a project goal of bench-scale testing of promising treatment technologies for Mercury removal from wastewater. The testing is to be performed by Suppliers of the technologies using a sample of hospital clinical laboratory wastewater. The testing is to include "systems" considerations for handling of interfering wastewater constituents and for optimization of the Mercury removal process relative to an effluent concentration goal in the order of 1 microgram per liter (µg/L). In the test report, the Supplier shall include discussion of the Mercury removal process relative to the need for (or advantages of) raw wastewater equalization, pH control, and biological sterilization and for final treated effluent neutralization. The discussion shall consider the allowed effluent pH range to be 5.5 to 10.5 Standard Units. The Supplier shall perform sufficient bench-scale testing to allow preliminary estimation of full-scale (24 hours/day) system capital and operating costs for wastewater flows of 2,000 gallons per day (GPD), 20,000 GPD, and 50,000 GPD. The Supplier shall detail the cost estimates in the overall test report and shall explain any omissions from or limitations in the estimates. The Supplier shall also estimate full-scale system space requirements (L x W x H) for each of the three flows along with a typical equipment layout diagram.
Attachment 2 provides information that you may want to consider prior to performing the feasibility testing.
Shipment of Raw Wastewater Sample from the Subgroup to Supplier
The raw wastewater sample (quantity to be determined) will be collected by the Subgroup from an existing collection tank and will be shipped to the Supplier via overnight express. At the time of collection, an aliquot of the sample will be taken and analyzed for total and dissolved Priority Pollutant Metals (antimony, arsenic, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium, and zinc) by the Subgroup. The analytical laboratory report will be faxed to the Supplier as near to the sample delivery time as possible. The sample is expected to have a Mercury concentration between 20 and 40 µg/L. Other chemical parameters shall be assumed to be similar to the results of a comprehensive characterization study that was previously performed by the Subgroup on a sample of the wastewater. The Supplier shall use proper equipment and sample handling procedures for personnel protection and safety when handling clinical laboratory wastewater. For scheduling purposes, the Subgroup will begin collection and shipment of the wastewater sample on or near February 24, 1997.
Quality Control
Verification of Proper Sampling and Analysis Techniques
(Note: The Subgroup acknowledges that the following quality control procedures may be cumbersome to the Supplier. If you have a QC program that is comparable to the one described below, please submit a description of the program for review by the Subgroup.)
Within five days after the Supplier has received the raw wastewater sample and empty sample bottles, the Supplier shall prepare for analysis:
10 high purity deionized water samples (500 ml sample volume required) prepared in the Supplier’s laboratory using the Supplier’s own high purity water supply and its own prepared sample bottles.
10 additional samples of the Supplier’s high purity deionized water collected in the sample bottles that the Subgroup supplies.
The Supplier shall send 5 of each type of sample to the Subgroup for analysis. The remaining ten samples shall be analyzed by the Supplier’s lab. Please fax these results to: Karen Rondeau, MWRA, at (617) 241-2301.
Procedural Blanks
A minimum of three procedural blanks (high purity water carried through the same sample handling procedure and processes as the samples) from each experimental run shall be performed.
Sample Handling and Analysis
The Supplier shall collect and analyze as many samples during testing as he/she deems necessary for determination and optimization of each element of system performance. At a minimum, the Supplier shall provide mercury data for each treatment step and final treated effluent for each test run. Please see Attachment 1, Guidelines for Sample Collection and Processing.
The Supplier shall indelibly and clearly mark each sample bottle label for identification of contents, test run, treatment step, date, and qualifying comments. These requirements apply to test samples intended for local analysis and, as outlined below, to test samples to be returned to the Subgroup.
The Supplier shall perform on-site preservation of test samples by addition of concentrated nitric acid to reduce sample pH to less than 2.0 standard units.
The Supplier shall perform EPA method 245.1 for total Mercury analyses with equipment and personnel capable of achieving a method detection limit of 0.2 µg/L.
In an overall test report, the Supplier shall include copies of all executed "chain-of-custody" sheets and analytical laboratory test reports. Each laboratory test report shall clearly identify sample contents, test run, treatment step, date, and qualifying comments. In addition, careful documentation and reporting of the result of sample preparation and analyses, including those of individual replicates and blank samples should be provided.
Samples to be sent back to the Subgroup
Along with the raw wastewater sample, the Subgroup will ship empty analytical laboratory sample bottles and "chain-of-custody" sheets. The Supplier shall submit to the Subgroup, the following samples for analysis:
5 high purity deionized water samples (500 ml sample volume required) prepared in the Supplier’s laboratory using the Supplier’s own high purity water supply and its own prepared sample bottles.
5 additional samples of the Supplier’s high purity deionized water collected in the sample bottles that the Subgroup supplies.
1 procedural blank from each test run.
A split sample of final treated effluent from each test run. A split sample is a subsample of the same sample that the Supplier analyzes.
Subgroup sample bottles intended for metals analyses will be so labeled by the Subgroup and will be inoculated with nitric acid prior to shipment. The Supplier shall check pH after filling and shaking the sample bottle and, if needed, shall add concentrated nitric acid to assure that the contained sample pH is less than 2.0 Standard Units for preservation until subsequent laboratory analyses by the Subgroup. The Supplier shall be responsible for ensuring that its testing staff exercises proper and safe handling of the sample bottles and nitric acid.
All filled Subgroup sample bottles shall be stored at 4oC maximum by the Supplier until shipment by overnight express (paid for by the Supplier) to the Massachusetts Water Resources Authority Central Laboratory. The deionized water samples shall be shipped back to the Central Laboratory in the cooler originally used for wastewater sample shipment. The Supplier shall refill the cooler with ice before shipment and shall pack the cooler to minimize the likelihood of sample bottle damage during shipment. The shipment shall be clearly labeled with "Project Code HGTECH" and shall be made to the following address:
Ms. Polina Eppelman
Massachusetts Water Resources Authority
Central Laboratory
Deer Island
Boston, MA 02152
Project Code: HGTECH
Feasibility Test Report
The Supplier shall issue the test report approximately four weeks after the conclusion of testing (i.e., around the end of March 1997). If possible, the following test report format shall be used:
Introduction/Background
Test Materials, Procedures, and Experimental Protocol
Pretreatment Considerations
Test Results
Full Scale System Considerations (Cost Estimates, Siting, etc.)
Discussion/Conclusions
. Appendices (including analytical test reports)
In the test report, the Supplier shall include descriptions of:
system process steps,
preferred Mercury speciation,
inactivation of complexing agents that could limit Mercury removal,
test Mercury removals through each process step, and
full-scale system operation and control considerations.
In the test report, the Supplier shall include discussion of the Mercury removal process relative to the need for (or advantages of) raw wastewater equalization, pH control, and biological sterilization and for final treated effluent neutralization. The discussion shall consider the allowed effluent pH range to be 5.5 to 10.5 Standard Units. The discussion shall also consider the rather large daily and hourly variabilities that, depending upon the clinical laboratory facility, could occur in the wastewater flow, pH, mercury concentration, and the presence and concentration of potentially interfering and mercury-complexing chemicals.
Contact Person for Public Document
Since the Subgroup is associated with the Massachusetts Water Resources Authority, an agency of the Commonwealth of Massachusetts, the test report will become part of a public document. Accordingly, the Supplier is invited to include name(s) of a contact person or persons with mailing addresses and telephone/fax numbers for future inquiries by other parties.
Recommended Guidelines for Sample Handling and Processing
Because the mercury content of samples, especially after pretreatment, may be close to or less than that detectable by EPA method 245.1, contamination during the collection and processing of samples may severely compromise the integrity of the analysis and subsequent interpretation of results of any experiments conducted. Contamination and analytical problems in analysis of trace concentrations of mercury are well known and provide significant challenges for most laboratories. The following are recommendations to minimize these potential problems:
Use extreme care in the collection and processing of samples. Typically the collection of several hundred mls for analysis is required, more if replicate analysis is to be conducted or sample splits prepared. Contamination from dust and residual vapor phase mercury, improper handling (plastic gloves should be used at all times), improperly cleaned labware and cross-contamination from samples with very high mercury concentrations are especially prevalent sources of error.
Labware in contact with samples should be cleaned by use of a common laboratory detergent and then acid-cleaned either in hot concentrated nitric acid or by soaking in 6M HNO3 overnight followed by thorough rinsing with high purity deionized water.
The use of Teflon or glass labware is preferred to minimize sorption losses. Sample containers (glass stoppered 500 ml Erlenmeyer flasks or 500 ml Teflon bottles are useful) should be stored in plastic bags after cleaning and after filling with sample to minimize the possibility of contamination. If possible, do not use sample bottles previously containing samples with high concentrations of mercury to collect samples you anticipate will have mercury at much lower levels (e.g. after treatment). After cleaning and in between use, store sample bottles filled with 10% HNO3 prepared using high purity deionized water.
Because many laboratories have difficulty in producing high quality results at 1 ug/l or lower, you may wish to pre-evaluate the capabilities of the laboratory ( and your ability to prepare clean sample bottles) by sending the lab you plan to use approximately five samples of your high purity water. If the results are erratic, you will need to evaluate whether the lab or your sampling technique is the source of error. Inability to consistently achieve mercury concentrations less than the detection limit in high purity deionized water samples should be of concern and perhaps require the use of another laboratory.
Additional Information Concerning Pretreatment Considerations
The Subgroup has obtained information regarding the field testing of an innovative mercury removal technology that is being conducted through the assistance of the Massachusetts Strategic Envirotechnology Partnership (STEP) program. The testing of this system has been underway for about four months. While this testing was conducted on scrubber wastewater from a medical waste incinerator, rather than clinical laboratory wastewater, it has yielded information which we feel would be useful to the Supplier in the performance of this feasibility testing:
Mercury speciation studies revealed that the forms in which mercury may be found are both complex and variable. The results showed that a significant amount of the mercury in the wastewater are bound to colloids and particulates in suspension (as much as 64% in one sample), or exists in the form of organic complexes.
Based on these speciation results, a number of pretreatment techniques were evaluated to either remove the non-binding forms of mercury or to release the bound mercury to allow the removal system to recover it: chlorination, using hypochlorite; ultrafiltration; activated carbon; and reducing the pH of the wastewater. The use of hypochlorite was found to be the best approach, resulting in significant improvement in the performance of the system. The system was consistently able to remove >99.5% of the mercury (at feed levels of 500 to 10,000 ppb) to discharge levels of under 5 ppb when hypochlorite was used. The optimal pretreatment was to add sufficient hypochlorite to reach a level of 1 - 5 mg/L residual chlorine with a 15 - 30 minute reaction time.
The initial work with hypochlorite used an ORP electrode to measure the residual chlorine level. This approach, however, was found to be somewhat inexact and time consuming, and was replaced with a wet chemical method using the DPD colorimetric test.