# Evidence for water contamination by effluents from steam

- and coal

- fired power plants: the need for zero liquid discharge limitation

Avner Vengosh and Laura Ruhl

Nicholas School of the Environment, Duke University

http :// sites.nicholas.duke.edu /

avnervengosh /

# Energy production in the USA ( 2011)

EIA

- US Energy Information Administration 

### Total production= 78 quadrillion Btu Renewable (12.3%)

# Electricity production in the USA (2011)

EIA

- US Energy Information Administration 

### Renewable (8%)

# Five hundreds power plants nationwide generate

approximately 130 million tons of coal ash each yearAs, B, Se, Hg

Combustion 

### Volatilization Retention of gases and volatiles by fly ash and treatment (FGD) Storage of coal ash in ponds

leaching



### Contamination of
water resources



# The cycle of contaminants: from fossil swamps to today waters coal

## The Roxboro Coal fired plant, North Carolina 1513 MCM (~ New York city )

(2558 megawatts) 

# Contaminants discharge to the environment

Cooling water



# Source: CCR effluents 

# Water quality NPDES outfall

# Evidences for water contamination from coal combustion products

• Extensive literature on laboratory coal ash leaching experiments has demonstrated the high mobilization of contaminants such as arsenic and selenium from coal ash.

• Specific case studies of spills or accidents (e.g., TVA coal ash spill, Kingston, TN).

• Monitoring the water quality of outfalls and downstream lakes and rivers in NC ( Ruhl et al., 2012)

## Experimental leaching of TVA coal combustion products: High levels of As and Se upon leaching with water

bulk fly ash bottom ash

### Coal Combustion Residues

As

Se Hg B Sr Li

Ra SO 4 

### Cr

Pb 

# Pollutants from coal combustion residues that could be released to the environmentDecember 22, 2008: retaining walls broke on a waste retention pond at the Kingston

coal Plant, Tennessee, and an estimated 4.1 million m 3 of coal ash slurry was spilled onto the land surface and into the adjacent Emory and Clinch Rivers 

# The 2008 TVA coal ash spill

Accumulation of coal combustion products in the river bottomSubsurface ash/ sediments; Pore water River water (As <10 ppb) 

### Discovery of hot spots: arsenic contamination in pore water from buried ash deposits within river sediments in the spill area

15

- 50 cm

River sediments Ecological threshold (150 ppb)

From Ruhl et al., 2010

# A national

- level issueRoxboro Plant at Hyco Lake

Mayo Plant at Mayo Lake Belews Plant at Belews Lake Dan River Plant on the Dan River

Asheville Plant at Lake Julian and the French Broad River

Riverbend Plant at Mountain Island Lake Marshall Plant at Lake Norman Allen Plant at Lake Wylie Reference Lake Jordan Lake Buck Plant at High Rock Lake 

### 9 sites, 1 reference lake

### Investigated coal

- fired electrical power plants, CCR effluent discharge through NPDES outfalls, and associated waterways in North Carolina

• Large variability in effluent flux

• With and without FGD scrubber system

# High As concentrations in some of the effluents from coal combustion residues ponds

Hyco Lake Outfall Effluents from coal ash ponds

FD FGD No FGD

### Enrichment factors of CCR effluents relative to upstream waters

As

Se Tl B

Two

- to three

- orders of magnitude of contaminants enrichment; Support EPA modeling for high contaminants levels in CRR effluents

### Conservative variations : Dilution in some cases can mitigates contamination

• The size of the water

resource

– mass

balance between CRR discharge flux and natural water flows;

• The nature of the contaminants (e.g., its solubility);Lake level 

### Redox

- sensitive contaminants are enriched in deep water associated with lake thermal stratification

oxic

anoxic

# Recycling of arsenic: long

- term accumulation in lake sediments: dilution cannot be the solution

Coal 

### Adsorption to particulates

accumulation 

### Pore water Discharge of CRR effluents

# Recycling of arsenic: long

- term accumulation in lake sediments: high As in pore water even in systems where As in CRR effluent is low

Pore water in lake sediments

FD FGD No FGD 

### Implications: reduction of contaminants level in CRR outfall is not sufficient to prevent contaminants’ accumulation in lake sediments and ecological food

- chain  zero liquid discharge is needed.

### Charlotte water treatment

Outfall (As=56 ppb) Mountain Island Lake Surface water=1 ppb; Pore water =100 ppb Suspended solids 

### d rinking water

sludge (30

- 70 mg/kg)

soil amendment



# ? The larger scale arsenic impact

Riverbed Steam Station

### Arsenic in sludge from Charlotte

- Mecklenburg treatment plant

Data from Sam Perkins, Catawba Riverkeeper Foundation Arsenic levels in sludge from treatment facilities in NC not associated with coal ash disposal  zero

### Results and implication

• This study shows that coal

- fired power plants and FGD wastewaters have significant high levels of contaminants and directly effect the water quality of receiving waters of North Carolina.

• We show that even low concentrations of some contaminants, such as As with concentrations below health benchmarks at the NPDES outfalls, could become problematic as As is retained in suspended sediments and remobilized with environmental changes in reduced bottom and pore waters. Dilution cannot be a solution.

• In every NPDES outfall we investigated we found elevated levels of contaminants; the test that was conducted in North Carolina applies to similar hundreds of coal ash ponds in the USA

- this is a national level problem

.

### Results and implications (continued)

• The results of this study have significant implications for hundreds of similar sites across the US given that CCR storage facilities continuously generate contaminants via leaching and transport to nearby hydrological systems. While this study focused on surface waters near CCR facilities, groundwater may have similar effects. Many CCR disposal ponds and landfills are not lined and, in many instances, are neither adequately monitored, nor regulated with respect to their effects on groundwater and surface waters.

• The evidence for direct contamination of water resources directly from NPDES outfall of CCR effluents highlights the need for rigorous monitoring and clear regulations for limiting the CCR contaminants that are being discharged into US waterways. Zero liquid discharge is the only solution that can stop the buildup of coal contaminants in the environment

.

# Further reading:

Ruhl , L., Vengosh, A., Dwyer, G.S., Hsu Kim H., Schwartz, G., Romanski , A., and Smith, S.D. (2012). The impact of coal combustion residue effluent on water resources: A North Carolina example. Environmental Science & Technology, 46, 12226

- 12233

.

Ruhl , L., Vengosh. A., Dwyer, G.S., Hsu

- Kim, H., Deonarine , (2010). The Environmental Impacts of the Coal Ash Spill in Kingston, Tennessee: An Eighteen

Month Survey. Environmental Science and Technology , 44, 9272

– 9278.

Ruhl , L., Vengosh. A., Dwyer, G.S., Hsu

- Kim, H., Deonarine , A., Bergin, M., Kravchenko , J. (2009). Survey of the potential environmental and health impacts in the immediate aftermath of the coal ash spill in Kingston, Tennessee . Environmental Science and Technology , 43, 6326

– 6333.



### http:// sites.nicholas.duke.edu/avnervengosh /

# Acknowledgements

• Nicholas School of Environment, Duke University

• National Science Foundation, Geobiology & Low

- Temperature Geochemistry Program