The overall objective of the validation study was to confirm that the ENVIRO-CLEAN PROCESS would meet the heavy metal effluent treatment objectives for the chromium waste water stream at the client’s plant, located in East Liverpool, Ohio. The validation study was performed July11 – 13, 1998.
Approximately ten (10) gallons of chromium waste (2 five gallon containers) were collected at the client’s facility on June 2, 1998. The waste sample was a light yellow-green color. A portion of the feed sample was collected and submitted for analysis; the analysis is presented in Table 1.
The balance of the chromium waste was processed through the ENVIRO-CLEAN PROCESS pilot carbon unit. The system consisted of a feed pump, pH controller and two (2) carbon columns. Each column contained about 180 grams of granular activated carbon, Filtrasorb 400 manufactured by Calgon Carbon. The flowrate was set at 20 ml/min with the feed solution pH controlled at 4.5. The treatment parameter values were based on positive results obtained from previous chromium removal projects. Effluent samples were collected and analyzed for total and hexavalent chromium and cobalt. The feed and effluent analysis are presented in Table 1, with the time periods marked in parenthesis, designating when the sample was collected during the test run.
Table 1. Heavy Metal Analysis
|Individual Samples||Total Chromium (mg/l)||Hexavalent Chromium (mg/l)||Cobalt (mg/l)|
|Feed 9:00 AM||11.8||1.14||0.07|
|Sample #1 (4 hrs)||0.10||<0.005||0.08|
|Sample #2 (8 hrs)||0.58||<0.005||0.16|
|Sample #3 (12 hrs)||0.07||<0.005||0.03|
|Sample #4 (16 hrs)||0.07||<0.005||0.11|
|Sample #5 (20 hrs)||0.55||0.022||0.17|
|Sample #6 (24 hrs)||0.52||0.013||0.23|
The processing of the chromium waste sample was completed without any mechanical or process difficulties. The effluent was crystal clear with no visible trace of solids or color.
ENVIRO-CLEAN PROCESS Results
The ENVIRO-CLEAN PROCESS was able to produce a low level chromium effluent and meet the client’s current discharge limits. The pilot unit’s average effluent concentration for total chromium averaged 0.31mg/l. The treatment system’s removal efficiency for total chromium and hexavalent chromium was 97.4% and 99.2% respectively. The ENVIRO-CLEAN PROCESS produced an effluent which meets or exceeds the client’s discharge limits for total chromium.
We feel that the effluent from the ENVIRO-CLEAN PROCESS can be recycled in the plant eliminating a significant quantity of water currently being discharged; one option is to recycle the water for in-plant rinsing needs. For cost estimating purposes, we are basing water saving figures on recycling 1,500 gallons per day at a cost of $2.50 per 1000 gallons. Most trends indicate that water and sewage rates are likely to continue increase.
Field Demonstration Test
Lewis Environmental Services conducted two on-site field evaluations at the East Liverpool, Ohio plant. A bench top unit was used to process individual waste samples on July 23 and August 27, 1998. Approximately 8 liters were processed during each 6 hour period. The samples were collected and submitted for analysis by plant personnel. The effluent analysis from the July 23, 1998 test for hexavalent and total chromium were <0.02 mg/l and 0.027 mg/l respectively. These results are well within the client s current discharge limits. The July 23, 1998 effluent test results are presented in Exhibit 1.0. The same granular activated carbon has been used in the bench top unit for all the various laboratory and field tests.