WATERtech 2010April 21-23, 2010, Fairmont Banff Springs

Pulp Mill Landfill Leachate Treatment –Chemistry and Regulatory Challenges

Presented by Dr. Francisco A. Perelló, P.Eng.

Table of Contents:• Site Background• Project Challenges & Leachate Sources• Leachate Treatment Plant• Permit Requirements • Effluent Characterization • Toxicity Identification Evaluation (TIE)

• TIE - Ammonia and pH• Issues Encountered• Solutions & Lesson Learned

Site Background – WFP Woodfibre

Location: Woodfibre, BC –part of the District of Squamish on Howe Sound.

Isolated work site with only boat or helicopter access.

Western Forest Products mill was shut down in 2006 and decommissioned in 2009.

Project Challenges• Remote• Tight project

timeline• H&S concerns• Active demolition• Confined spaces• Leachate toxicity• Regulatory

requirements

Leachate SourcesLandfill accepted following wastes

from the Kraft mill process.

• Wood residue / waste• Boiler ash• Dreg washer reject• Lime slaker reject• Lime kiln reject• White liquor (sodium hydroxide

and sodium sulfide) • Black liquor (lignin fragments,

hemicellulose, sodium carbonate, sodium sulfate and other inorganic salts)

• Residual scrap metal• WWTP residues• Miscellaneous chemicals

(sulphuric acid)

Treatment ComponentsAERATION• Primary and secondary aeration• Coarse bubbling aeration for

sulphide removal• Fine bubbling aeration for DO

increaseMETAL AND SOLID REMOVAL• Flocculation• Sand filtration• Settling tanks

Treatment ComponentspH CONTROL• CO2 injected prior to flocculant

addition and post sand filtration

REMOVAL OF DISSOLVED ORGANICS• Using GAC in pressurized vessels

Permit Requirements

BC Ministry of Environment (MOE)– TSS less than 45 mg/L– BOD less than 60 mg/L– DO more than 2.0 mg/L– T less than 40oC– pH between 5.5 and 8.5– Toxicity 100% Rainbow Trout 96-hr LC50 – Metals BC Water Quality Guidelines

Effluent CharacterizationLandfill Treated Percent

Permit Parameters Leachate1 Water2 Reduction (%)3

pH pH units 10 7.4 26Total Suspended Solids mg/L 58 7.8 87Biochemical Oxygen Demand mg/L 192 17.5 91Dissolved Oxygen (minimum) mg/L 1.4 2.6 -86

Other ParametersTotal Ammonia Nitrogen mg/L 16.7 6.3 62Nitrate ug/L <10 <10 0Nitrite ug/L <2 <2 0Sulphides ug/L 18200 1020 94Total Resin Acids ug/L 228 27 88Total Fatty Acids ug/L 224 85 62Tannins and Lignins mg/L 61 11.2 82Dioxins and Furans pg/L < detect n/a n/aMetals (included on next table)

Notes1) Pre Treatment Plant Installation Average Results2) Treated Discharge Average Results3) Negative percent reduction indicates an increase at discharge

Effluent CharacterizationLandfill Treated BCWQG3 Percent

Metals Parameters Leachate1 Water2 Reduction (%)Aluminum ug/L 2290 678 n/a 70Arsenic ug/L 19 6.2 5 67Chromium ug/L 22 7.3 8.9 67Copper ug/L 6 3.9 20 35Iron ug/L 407 332 300 18Mercury ug/L 2 0.1 0.1 95Nickel ug/L 105 20 25 81Selenium ug/L 1 0.7 2 30Vanadium ug/L 42 12 20 71Zinc ug/L 12 7.6 33 37Dissolved Al ug/L 952 298 100 69

Notes1) Pre Treatment Plant Installation Average Results2) April to June 2009 Discharge Average Results3) BCWQG - BC Water Quality Guidelines

Effluent Characterization

Variability in:

• Influent flow –groundwater and surface water

• Chemistry –new materials into the landfill during Site demolition

Treated Effluent Quality

• Effluent complied with most regulatory requirements• Treatment plant effluent regularly failed Rainbow Trout 96-hr

LC50 Toxicity Test in 2008.

• Adjustments were made to the operating system (secondary pH, secondary aeration, chemical flow rates, etc.).

• These changes led to improvements in solids removal, pH adjustment, DO concentration and metals removal.

• Marginal effects on improving effluent toxicity.

• In January 2009, it was decided to conduct a Toxicity Identification Evaluation (TIE).

Toxicity Identification Evaluation –Phase 1

• The TIE identified that the treated leachate toxic components were not organic, anionic elements, oxidizing compounds, or cationic metals.

• The toxicity correlated with samples where the pH increased to at least 8.6 or greater.

• According to the US EPA Phase 1 TIE manual, the level of concern for Ammonia is over 5 mg/L.

• The Total Ammonia Nitrogen was measured at 6.2 mg/L.

Toxicity Identification Evaluation –Phase 1

• At pH 8.8, the percent unionized ammonia (14.7%) is roughly double that at pH 8.5 (8.0%)

• The results of the TIE testing suggested Ammonia in combination with an increasing pH was leading to the failure of the test. Strontium was also considered a possible toxic component at this stage.

TIE – Ammonia and pHUnionized Component of Ammonia

Toxic vs Less Toxic Ammonia Shift

Unionized Ammonia

Ionized Ammonia0

0.2

0.4

0.6

0.8

1

1.2

7 7.5 8 8.5 9 9.5 10

pH

Am

mon

ia (m

g/L)

Toxicity Identification Evaluation –Phase 2

• The TIE Phase 2 aimed at filtering out the toxic components to verify the findings of the TIE Phase 1.

• Strontium was eliminated as a suspect toxic component. • It was confirmed that Ammonia combined with an increased

pH through the testing process was causing toxic effects that were observable later in the testing process.

• The pH in the lab increased from between 7.0 and 7.3 up to a final pH of 8.7 over 96 hours.

TIE – Ammonia and pHBCWQG Marine Guidelines

Concentration of Total Ammonia Nitrogen for Protection of Saltwater Aquatic Life

Maximum Conc. BCWQG for Ammonia (mg/L)

at pH 7.0 135 at pH 7.6 35 at pH 8.6 3.7

30 Day Avg. Conc. at pH 7.0 21 at pH 7.6 5.3 at pH 8.6 0.56

Average Treatment Plant Conc. 6.3 (Average pH 7.4)

NotesAll values shown at the average discharge temperature of 10oCAll values shown at typical salinity of 20 g/kg

TIE – Ammonia and pHUnionized Component of Ammonia

From Emerson et al., 1975, Journal of the Fisheries Research Board of Canada, 32, p. 2382.Reprinted by permission.

63.335.314.75.161.690.5420.1720.0540.0179

61.433.513.74.791.570.5010.1590.0500.0168

59.531.712.84.441.450.4620.1470.0460.0157

57.630.011.94.111.340.4270.1350.0430.0146

55.628.311.13.801.230.3940.1250.0400.0135

53.526.710.33.521.140.3530.1150.0360.0124

51.525.19.603.251.050.3350.1060.0340.0113

49.423.68.903.000.9680.3080.09770.0310.0102

47.322.18.252.770.8910.2840.08980.0280.0091

45.320.77.642.550.8200.2610.08260.0260.0080

10.09.59.08.58.07.57.06.56.0(°C)

pHTemperature

Table 11-4, A Percentage of the total ammonia nitrogen (TAN) that is present as unionized ammonia (UIA) at various temperature - pH combinations in freshwater.

Issues - Analytical

Toxicity testing procedure believed to be causing the toxic effect.

• The Rainbow Trout 96HR LC50 requires constant aeration of the samples as part of the procedure.

• The aeration is stripping out the CO2 which is added to neutralize the leachate pH.

• This causes the pH to rise through the test, which leads to an increase in the unionized portion of Ammonia.

• The unionized portion of Ammonia is the toxic component.

Issues - Analytical

• TIE Test results showed that all samples pH buffered to remain below 8.0 during the tests passed the Rainbow Trout 96HR LC50.

• This matched observations where fish mortalities only begin to occur when the pH reaches 8.6 at the later stages of the testing.

Issues - Regulatory

• At the project initiation, it was requested to BC MOE that the 96 hour LC50 rainbow trout test be adjusted.

• The request was not accepted because MOE required consistency throughout testing.

• After TIE Phase 2, we searched for a technical solution instead of approaching the regulators, which was based on prior interaction with the regulators and at the client’s request.

Toxicity Identification Evaluation –Phase 3

• Zeolite filter media was tested in the TIE Phase 3 to reduce ammonia concentrations.

• Used bench-scale columns to replicate in-field conditions.

• Unionized ammonia concentrations were reduced to non-toxic levels in lab conditions.

Field Results• Zeolite filter media

decreased ammonia initially.

• Ammonia < 5 mg/L during the first 24 hours of lab testing and no fish mortality.

• Ammonia concentrations still rose to toxic levels over the 96 hour test period.

Zeolite filter media

Conclusions

• The results from the three phases of the TIE indicated that the effluent is not toxic when discharged from the treatment plant.

• We concluded that the testing procedure changed the wastewater chemical composition which resulted in a toxic effect.

Solution

1. Presented lab results from TIE tests to MOE.2. MOE agreed to a new testing procedure Procedure

for pH Stabilization During the Testing of Acute Lethality of Wastewater Effluent to Rainbow Trout.

3. Presented the procedure to the laboratory, modified the sampling and analytical procedures.

• Adjust the analytical protocol so that pH does not increase during the test procedure.

Procedure for pH Stabilization

• The purpose of pH stabilization is to replace the CO2 lost due to aeration in order to maintain the pH throughout the test at the same levels found in the initial samples.

• Three techniques can be used as add-ons to the EPS 1/RM/13 test:– CO2 injection– Recycling– pH controller

MOE Requirements for new Procedure

• In order to use the “new” procedure, effluent characteristics had to meet three conditions:

1. Total ammonia must be measured on all effluent samples submitted for testing for acute lethality test using rainbow trout (EPS 1/RM/13).

2. Effluent must have failed the EPS 1/RM/09 test on a previously collected sample.

3. Effluent may not have an un-ionized ammonia concentration of ≥1.25 mg/L at 15°C or when the total ammonia concentration does not equal or exceed the maximum total ammonia concentration (y) in mg/L determined using the formula:

y=1.25x(10(9.564136638-pH)+1)

and the initial pH of the effluent at 15°C.

Results

• After pH stabilization, 100% of the effluent samples passed toxicity testing.

• Un-ionized ammonia concentrations remained below toxic levels.

Lessons Learned

• TIE provided a stepwise approach to eliminate COCs not linked with the effluent toxicity.

• TIE helped in identifying COCs causing effluent toxicity results.

• Lab procedure produced false positive results.

• Working with the regulators allowed us to modify the approved lab procedure.

• Revised lab procedure is a better representation of actual conditions. It confirmed that the effluent wasn’t/isn’t toxic.

Thank YouQuestions?