CE 510Hazardous Waste EngineeringDepartment of Civil EngineeringSouthern Illinois University Carbondale

Instructor: Jemil YesufDr. L.R. Chevalier

Lecture Series 4: Source Analysis

Course Goals Review the history and impact of environmental laws

in the United States Understand the terminology, nomenclature, and

significance of properties of hazardous wastes and hazardous materials

Develop strategies to find information of nomenclature, transport and behavior, and toxicity for hazardous compounds

Elucidate procedures for describing, assessing, and sampling hazardous wastes at industrial facilities and contaminated sites

Predict the behavior of hazardous chemicals in air, surface impoundments, soils, groundwater and treatment systems

Assess the toxicity and risk associated with exposure to hazardous chemicals

Apply scientific principles of hazardous wastes management, remediation and treatment

Fundamental Concepts CoveredMaterials Balance/Waste AuditsHazardous Waste Site AssessmentsSource Sampling: Statistics

Materials Balance/Waste Audits

Industrial Facility

Losses:Incorporated into Product

VolatilizationSpillage

Water treatment chemicalsCatalyst

Lubricating Oils

Maintenance Material

Laboratory chemical wastesSpent Chemicals

Spent and dirty filters

Waste Oil

See Figure 4.2 p. 214

Overall Strategy Convert to mass Convert to mass flux Cannot add concentrations Mass In – Mass Out + Rxn = Accum.

Materials Balance/Waste Audits

Problem 4.2 in TextThe following records are available for a small company that manufactures semi-conductors. The chemical used most at the plant is TCA, and the primary loss mechanism is volatilization. Using the following data, estimate the maximum volatilization rate.

Note: S.G. of TCA = 1.339Acquisitions:   RCRA Manifests:    Date Vol. (L) Purity (%) Date Waste No. Vol.(L) C (%)8-Jan 208 92 28-Feb F001 1140 226-Feb 833 95 20-Apr F001 386 1326-Feb 416 88 21-May F001 462 4515-Mar 208 97 30-May F001 1287 3611-Apr 208 90    2-May 625 95        

Discharges:            

Wastewater characteristics: 18.9 x 106 L/day (5 MGD) at 0.5 mg/L TCA

Solution1. Acquisitions:

(208 L)(1.339 kg/L)(0.92) + . . .= 3122 kg

2. Wastewater discharges

= (18.9 x 106 L/day)(143 days)(0.5 mg/L) (1kg/106 mg) = 1351 kg

3. RCRA Manifests:= (1140 L)(1.339 kg/L)(0.22) + . . .= 1302 kg

Solution4. Total Mass of TCA leaving the facility:

= 1351 kg + 1302 kg= 2653 kg

5. Total TCA volatilized:

= 3122 kg – 2653 kg = 469 kg

6. Volatilization rate:= (469 kg)/(143 days) = 3.3 kg/day

......end of example

Problem 4.3 in TextA plastic formulation facility receives one of its synthetic chemicals, dimethyl phthalate, by steady flow through a supply pipe at a flow rate of 200 L/day. The dimethyl phthalate is used in synthesis reactors for making a plasticized polymer at a rate of 0.8 moles/min. Partially reacted polymers are precipitated from specific reactions containing fluids with 1200 mg/kg (dry wt.) dimethyl phthalate. If 30,000 kg of the sludge (with an average water content of 85%) are generated each day, how much dimethyl phthalate is unaccounted for?

Note: S.G. = 1.191, MW = 194 g/mole

Solution1. Mass balance: In – Out + Rxn = Accum.

If Out = 0 thenIn + Rxn = Accumulated

2. Determine the mass of dimethyl phthalate supplied

(200 L/day)(1.191 kg/L) = 238.2 kg/d

Solution3. Determine the mass lost due to the reaction

(0.8 moles/min)(194 g/mol)(60 min/hr)(24 hr/d) = 223.5 kg/d

In + (-Rxn) = 238.2 – 223.5 = 14.7 kg/d

4. Determine the mass of dimethyl phthalate in the sludge

(1200 mg/kg)(30,000 kg/d)(0.15) = 5.4 x 106 mg/d = 5.4 kg/d

5. Mass unaccounted for:14.7 kg/d – 5.4 kg/d = 9.3 kg/d

......end of example

Hazardous Waste Site Assessments Phase I

Paper research (background search) Chemical inventory evaluation Interviews with current and former

personnel Interviews with community Regulatory agency record searches Title searches Areal photographs Permits and violations If suspicions of hazardous waste

contamination are confirmed, Phase II is warranted

Phase II Finalizing any searches that were

incomplete in Phase I Detailed evaluation of pathways and

potential receptors Random sampling and analysis If contamination occurred, Phase III

Hazardous Waste Site Assessments

Phase III Determine the extent of

contaminationArea, volume, concentration

With appropriate sampling designs, contaminant concentration data over depth and area Provides sufficient information to assess

the site hazard (need for site cleanup)Provides criteria for the design of

remedial process

Hazardous Waste Site Assessments

Source Sampling: Statistics Homogeneous source

Aqueous waste in a drum No concentration gradients No layering from density difference One sample represents the waste

Most hazardous waste is heterogeneous Sludges Soils Lagoons Characterization of the waste is expensive

Reliable analysis with sophisticated instrumentation Quality Assurance Report preparation

Two fundamental statistical concepts for sampling plan: Accuracy

How close a measured value is to the true value

Error allowed, a Corresponding parameter is the confidence

level (1-a) Precision

Measure of the variability between samples D, deviation from the true value – precision

requirement

Source Sampling: Statistics

Population True value of global data A number that describes a population is called

a parameter Parameters include

Mean, m; Variance, s2 ; Standard deviation, s Sample

Data set collected from population A number that describes a sample is called a

statistic statistics include

Average, x; Sample variance, s2 ; Sample Standard deviation, S.

Source Sampling: Statistics

Why sample the source material (population)? Sampling errors and analytical errors?

Which one is greater and why? If we take a sample and calculate a statistic, we often use

that statistic to infer something about the population from which the sample was drawn.

Source Sampling: Statistics

Source Sampling: Statistics

Degrees of freedom:A parameter used in statistical distributions that represents the sample size minus the number of parameters being estimated

df = n-1

1

22

nXX

S

nX

x

i

i

Sampling procedures Search sampling (historic information)

Using prior knowledge of the site Probability sampling

Designed so that samples which have an equal chance of being chosen are collected

Simple random sampling Stratified random sampling

A series of simple random sampling stacked on top of one another

Others

Source Sampling: Statistics

Probability Sampling Based on the t-distribution A probability density function that is used to

evaluate sample means when the population variance (σ2) is not known but can be estimated by S2.

nSXt m

This value is found in tables.Need to know the size of the sample set and the confidence level desired.

i.e., t = (df, α)

See Appendix E.

Determining sampling pointsDivide source area into a grid of

sampling units (blocks)Assign a number to each block of

the gridUse a random number generator to

determine sampling points

Determining the number of samples Initial or previous data Determine average and S2

Determine the student’s two sided t with n-1 degrees of freedom for a confidence level of (1-a)%

Determine the regulatory threshold, RT (e.g. toxicity characteristic leaching protocol (TCLP))

RTXDwhere

DStn

2

22

Confidence Interval (CI)

21nStXCI 2a

This parameter is needed to determine whether or not a hazardous chemical is present at concentrations which are measured below RT.

Procedure for the Simple Randomized Sampling of RCRA Hazardous Waste Sources

Collect a 3-6 random samples to obtain preliminary estimates of the average and variance

Estimate the minimum number of samples using a specified confidence interval

Using a sampling grid and random number assignments, collect and analyze at least the minimum number of samples from the waste source

RTXDwhere

DStn

2

22

Determine the average and variance from the detailed sampling plan

If the sample mean is ≥ the regulatory threshold (RT), the compound is present in hazardous concentrations

If the sample mean is ≤ RT Determine the confidence interval If the upper CI < RT, the compound is not

present

Procedure for the Simple Randomized Sampling of RCRA Hazardous Waste Sources

Class example from Text:A drying bed holding sludge from an electroplating process is to be sampled for cadmium content. The dimensions of the drying bed are 6 m X 6 m, and the sample volume will require an area 40 cm X 40 cm. Five preliminary samples were collected randomly with the following results: 25, 36, 49, 28, and 48 mg/kg Cd. Based on this information, develop a simple randomized sampling scheme. Determine (1) number of samples required for 95% confidence limits within 5 mg/kg of the sample mean, and (2) the location of the samples in the sludge bed.

SolutionFor the five preliminary samples,

1.11123

1231

)(

375

4828493625

5

1

2

2

S

andn

XbarXS

CdkgmgXbar

ii

SolutionFrom the Student’s t table (Appendix E), for df =n-1=4, and using α = 0.025, t95% = 2.776. Note that 2α=5%, error level for 95% confidence level).

The number of samples (n) is:

.38

9.375

)123()776.2(2

2

2

22%95

samplestoupround

samplesD

Stn

SolutionThe number of sampling units in both directions is:8 m/0.4 m = 20 unit, and6 m/0.4 m = 15 unitsTotal sampling units is 20 x 15 = 300.

Then select 38 random number between 1 and 300.MS Excel has a built-in function RANDBETWEEN().

RANDBETWEEN(1, 300) at 38 cells will generate 38 sampling locations in the 20x15 grid.

......end of examplespreadsheet

Stratified Random SamplingStrategy involves dividing a site

into layers or strata (subpopulations)

Strata are evaluated separately Increases sampling precision for

the entire population For soils, the strata are simply

horizontal layers at different depths

Stratified Random Sampling

n

yy

n

1ii

Mean for each strata is determined by:

The mean over all strata is:

N/yNyL

1hhh

whereL = total number of strataNh = total number of sampling units in the hth stratumN = total number of sampling units in all strata

Stratified Random Sampling

hn

1i

2hi

hhh

2h

h yy1nn1

nSyV

Sample variance within each stratum:

Variance of the sample mean over all strata:

L

1h h

2h2

h2 nSNN

1yV

Summary of Important Points and Concepts Waste audits, which are based on

materials balance, can be used to determine losses from volatilization, spillage, authorized removals to secure landfills or incineration, or improper management.

Waste audits also serve as a basis for waste minimization and pollution prevention plans.

Assessment of contaminated sites is based on a multi-step approach, with each phase characterized by succeeding complexity. (Phase I, II, and III)

Summary of Important Points and Concepts

Source materials, such as soils and sludges, are most effectively sampled using probability sampling.

Simplified random sampling is used in system which there is no gradient in contaminant concentration with depth. It is also the basis for probability sampling.

Stratified random sampling is used to sample systems where different strata contain a range of concentrations.