Circumix Dense Slurry System (DSS) for Ash and Waste Water Management

and How it Addresses Proposed ELG and CCR Rule Changes

Technology Description

Circumix Dense Slurry System (DSS) is a high-intensity process that mixes minimal quantities

of waste water with CCR’s to produce dense, pumpable slurry. This process maximizes the

availability of reactive ions in ash products resulting in near-stoichiometric use of the slurry

water. Additives (while not necessary) may enhance end product performance depending upon

the chemistry of the ash to be stabilized. Once discharged, the slurry sets within 24 to 72 hours.

Once cured, the product exhibits low hydraulic conductivity, high compressional strength, no

waste water discharge, little or no fugitive emissions and enhanced sequestration of metals.

NAES Corporation is in partnership with GEA EGI Contracting/Engineering Co. Ltd.

(technology developer) in Hungary to deploy the technology in the United States.

In one process, this technology addresses ELG and CCR rule changes by facilitating:

1. Effective combined stabilization of ash and waste water,

2. Reduction of water use by 80% to 90% compared to traditional “lean slurry” practice,

3. Zero discharge of transport water & leachate (if leachate is re-used for DSS),

4. Reduction of plant-wide waste water volume destined for treatment and discharge,

5. Enhanced protection of ground water by virtue of low hydraulic conductivity (measured

10-4 to 10-10 cm/sec) and enhanced metals sequestration exhibited by the end product,

6. Elimination of risk of catastrophic releases associated with dike failure and liquefaction

because of the solid nature and high compressive strength of the end product,

7. Significant reduction of leachate volumes due to low hydraulic conductivity, high

capillary retention, hydration reactions and because of low water use for the process.

8. Significant reduction of fugitive dust emissions due to the initially wet nature, enclosed

transport medium and later solid nature of the end product,

9. Enhanced land-use efficiencies for disposal sites because the high compressional strength

of the end product facilitates elevated impoundments and landfills,

10. Reduction in the cost of managing CCRs and waste water compared to “dry ash”

management and water treatment alternatives referenced by EPA in the proposed rules.

11. Reduced energy usage and labor requirements for pumping dense slurry compared to

“dry ash” management which typically requires pug mill mixing, hauling by truck and

spreading/compaction by heavy equipment.

12. Enhanced safety of operations and noise levels because the dense slurry can be pumped

rather than transported by truck and/or manipulated with heavy equipment.

In summary, DSS achieves the goals and objectives of the proposed ELG rules and CCR rules in

one process by converting waste water and CCRs into an environmentally stable end product.

Historical Use

DSS is not new. It has been used for decades in Europe and since 2003 in the United States.

Table 1 lists the coal-fired power plants that are currently employing or have employed DSS

technology. This table includes pertinent data on types and quantities of ash treated (per hour

and total); when DSS processing was initiated, etc.
Page 2 of 11

Table 1. Summary of Global Dense Slurry Commercial Application

Reference

Plant Country

Plant

Capacity

(MW)

Plant

Ops.

Working

Hours /

Year

Bottom

Ash TPH

Fly

Ash

TPH

FGD

Handled

(Yes / No)

DSS Flow

Rate (m3/h)

Total Dense

Slurry (m3)

Pannon

Hőerőmű Zrt.

Hungary 200 1991-

2000 6,000 38.8 155.2 No 120 6,480,000

Tatabányai

Erőmű Kft.

Hungary 30 1993-

2000 4000 - 20 No 30 840,000

AES Borsodi

Energetikai Kft. Hungary 200 1996-2000 6,000 24 156 No 200 2,400,000

Matra Hungary 836 1998- 8,000 80 640 Yes 480 23,040,000

SC Collterm SA Romania 50 2000- 3,500 3 20 No 30 1,050,000

Jacksonville

Northside

Generating

Station

USA 600 2003- 8,000 125 125 Yes 120 6,720,000

SC Collterm SA Romania 50 2002- 3,500 3 17 No 30 840,000

Rovinari Power

Plant Romania 1 720 2010- 8,000 120 508 Yes 230 1,140,000

Craiova II.

Power Plant Romania 300 2010- 8,000 18.4 204 Yes 95 760,000

Isalnita Power

Plant Romania 630 2010- 8,000 28 220.8 Yes 100 466,600

Spectrum Coal

and Power India 50 UnderConstruct. n/a 15.6 36.4 No 80 -

Turceni Romania 1320 Under

Commiss. n/a 120 440 Yes 235 -

Total 5,986 43,736,600*

* As of Spring 2012
Page 3 of 11

The JEA plant (the only U.S. plant that uses DSS) employs two DSS mixing systems that

collectively process 120 tons per hour of fly ash and bottom ash. Following mixing and

discharge of the dense slurry, JEA interrupts the hydration process by excavating and drying the

dense slurry. Following additional preparation steps, JEA markets this material for beneficial

use as a road construction material with the trade name: EZ Base. The JEA ash exhibits

favorable chemistry for beneficial use and demonstrates the potential for beneficial use of other

types of ash with or without additives designed to enhance end product performance.

EZ Base was tested in Florida as a road surfacing material (not an underlayment) and monitored

to evaluate its environmental stability. Following baseline sampling and road construction using

EZ Base paving material, adjacent soil, ground water, storm water and surface water were

monitored for two years by an independent engineering company. The results were reported in

November 2011. The results of this monitoring showed that there was no statistical change in

any of these environmental media during the two year monitoring period. This report is entitled:

Year Two Follow-up Investigation Report, Soil and Water Quality Evaluation, St. Mary’s Shoals

Park Roadway Improvements, Baker County, Florida. The report was prepared by Mechling

Engineering & Consulting, Inc., Jacksonville, FL and can be obtained from the Florida

Department of Environmental Protection.

Figure 1 shows the active impoundment at the Matra Plant in Hungary. The impoundment has

been in operation since 1998 and consists of 15 tiers averaging 10 ft. each comprised of

successive layers of solidified ash that was pumped to the impoundment as dense slurry from the

plant in the background. It covers an area of 314 acres at its base and 122 acres at the top. The

impoundment has been tiered and elevated an average of 150 ft. above the impoundment base.

The steepness of the impoundment slope and height of the impoundment are determined in part

by the compressional strength of the solidified product. The compressional strength, in turn, is

determined by the chemistry of the dense slurry ingredients. This impoundment poses no risk of

catastrophic failure or inundation of the surrounding community by liquefaction of ash products

because the compressional strength of the solidified products comprising the impoundment

ranges from ~5000 to 11,000 lb/ft3(Table 11). There have been no slope failures or other

incidents requiring remedial action since this impoundment was built and all leachate is returned

to the plant for DSS processing. Thus, this is a zero discharge impoundment with respect to

transport water and leachate.
Page 4 of 11

Figure 1. Elevated Solidified Ash Impoundment Containing ~ 25 million m3of DSS Product

It is important to point out that the DSS process results in a product that exhibits:

 Hydraulic conductivity that is substantially lower than that resulting from traditional “dry

ash” management as described in the proposed rule,

 80-90% less consumption of water compared to traditional sluicing ,

 Stabilization of waste water (including FGD water) to produce the dense slurry,

 Zero discharge of transport water

 Zero discharge of leachate if re-used for DSS,

 Enhanced sequestration of contained metals,

 Reduced risk of ground water contamination,

 Reduced quantities of leachate produced,

 Reduced or substantially eliminated risk of dust generation,

 High compressive strength,

 Enhanced use of disposal space because disposal facilities may be tiered and elevated,

 Enhanced worker safety due to reduction or elimination of trucks and heavy equipment

for transport and manipulation of ash products,

 Simplified and lower risk closure results,

 Elimination of risks for liquefaction of ash sludge and catastrophic releases associated

with dike failures.
Page 5 of 11

So, from the perspective of environmental protection, DSS is a superior process compared to

“dry ash” management as described in the proposed rule. It is also safer and less expensive.

Ash Testing

NAES and GEA EGI have established a testing program to conduct DSS testing on combustion

products and waste water from North American coal plants. The testing program will tailor a

“recipe” to the plant’s specific ash and waste water chemistry. Testing will establish the

environmental performance of the solidified product and will facilitate evaluation of the

feasibility and economics of converting an existing wet ash management system to DSS. Figure

2 shows the 1.5 ton/hour pilot scale system that can be mobilized to a plant to test materials on

site or which can be used to conduct testing anywhere else.

Figure 2. Skid-mounted mobile dense slurry test system.

Supporting Data

The following tables present data from chemical analyses performed on water and process

residuals used to produce dense slurry. In addition, data from testing of solidified and cured

dense slurry produced from these waters and process residuals is provided. The data on

solidified products includes hydraulic conductivity, compressional strength; total metals content,

and leach performance. These data originate from two testing programs involving two general

sources of water and process residuals. These include:

1. Matra Plant: This is an 880 MW lignite-fired plant located in Hungary. A series of tests

on ash and water were conducted as part of the Circumix system evaluation.

2. Mibrag: Black and Veatch Engineering Services conducted an independent evaluation of

ash and FGD water disposal options for 4 plants in Germany involving different varieties

of German coal. The Power Client was Mitteldeutsche Braunkohlengesellschaft GmBH

(shortened to Mibrag).
Page 6 of 11

Table 2 presents the compositions of the various ash products used to produce dense slurry

products in the Mibrag testing program. Tables 3 and 4 show the respective compositions of the

FGD and process make-up water used in the Mibrag dense slurry mixtures. Table 5 shows the

leach performance from numerous solidified dense slurry samples from Mibrag. Table 6

presents the hydraulic conductivity and compressional strength from the solidified dense slurry

Table 2. Normalized Ash Compositions for Mibrag Dense Slurry Tests

Oxide Wt % of Oxide

CaO 38.10 37.70 15.36 60.38 37.33 40.22

SiO2 29.10 29.54 58.71 13.34 29.23 30.04

MgO 4.55 4.40 2.45 2.21 5.15 4.64

Al2O3 11.85 11.60 16.73 4.41 11.57 7.26

Fe2O3 5.08 5.91 3.13 2.51 6.31 7.36

SO3 11.32 10.85 3.62 17.15 10.41 9.78

Na2O 0.00 0.00 0.00 0.00 0.00 0.50

K2O 0.00 0.00 0.00 0.00 0.00 0.20

Total* 100.00 100.00 100.00 100.00 100.00 100.00

Table 3. Mibrag FGD Water used in Dense Slurry

Parameter Units Value

pH 7.6

Conductivity mS/cm 22.6

Total Solids mg/l 57100

TSS mg/l 9620

Cl mg/l 6100

F mg/l 89.7

NO2 mg/l 0.15

NO3 mg/l 1080

PO4 mg/l 1.63

SiO2 mg/l 25.2

SO4 mg/l 15000

Arsenic mg/l <0.001

Lead mg/l <0.04

Cadmium mg/l 0.08

Calcium mg/l 715

Chromium mg/l ,0.05

Cobalt mg/l 0.05

Magnesium mg/l 5855

Nickel mg/l 0.38

Mercury mg/l <0.0005

Selenium mg/l 0.166

Thallium mg/l <0.02

Zinc mg/l 1.4
Page 7 of 11

Table 4. Make-up Process Water Properties used for Mibrag Dense Slurry

Parameter Units Value

pH 12.7

Conductivity mS/cm 8.8

Ca2+ mg/l 1200

Fe mg/l 0.1

K

+ mg/l 29.6

Mg2+ mg/l <1

Na+ mg/l 290

NH4

+ mg/l 0.4

Cl- mg/l 820

NO2

- mg/l 0.5

NO3

- mg/l 5.8

PO4

3- mg/l 0.1

SO4

2- mg/l 1250

SiO2 mg/l 0.5

Table 5. Leach Performance* of Solidified Dense Slurry from Mibrag Ash and Waste Water

Parameter Units I-2 I-3 II-1 II-2 II-3 III-1 III-2 III-3 IV-2 IV-3 V-1 V-2 V-3

pH 12,7 12,7 12,6 12,2 12,6 11,9 12 12 13,1 12,9 12,9 12,9 12,7

Conductivity mS/cm 4,27 3,91 3,66 2,18 3,83 1,01 1,25 1,71 8,84 9,67 6,65 7,33 7,35

TDS mg/l 0,9 0,3 1,6 1 0,7 1 0,9 0,9 2,5 3,4 1,7 1 1,3

Arsenic μg/l 1,6 2,1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

Lead μg/l <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10 <10

Cadmium μg/l <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 <1

Chrome μg/l <20 <20 <20 <20 <20 <20 <20 <20 <20 <20 <20 <20 <20

Copper μg/l <50 <50 <50 <50 <50 <50 <50 <50 110 100 <50 <50 100

Nickel μg/l <20 <20 <20 <20 <20 <20 <20 <20 <20 <20 <20 <20 <20

Mercury μg/l <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 0,5 <0,5 <0,5 <0,5 <0,5

Zinc μg/l 170 170 190 110 170 90 90 110 370 370 230 170 280

Ammonium mg/l 0,11 0,12 0,06 0,04 0,07 0,04 0,01 <0,01 <0,01 <0,01 0,25 0,07 0,18

Chloride mg/l 121 342 -- 17,4 60,8 21,9 67,5 198 168 490 94,6 60,8 180

Cyanide mg/l <0,01 <0,01 <0,01 <0,01 <0,01 <0,01 <0,01 <0,01 <0,01 <0,01 <0,01 <0,01 <0,01

Fluoride mg/l 0,11 0,27 <0,1 <0,1 <0,1 <0,1 <0,1 0,28 11,5 17,6 <0,1 <0,1 0,22

Sulfate mg/l 72,8 71,1 no data 38,3 33,6 91,3 97,1 47,6 1180 1120 84,5 33,6 131

* Leach Test Procedure: DIN 38 414 S-4
Page 8 of 11

Table 6. Mibrag Compressional Strength & Hydraulic Conductivity of Cured Dense Slurry

DSS Mix

Water *

Cure Time

(days)

Sample ID Water:Ash

Ratio

Hydraulic

Cond.**

(cm/sec)

Wet

Density

Compressional

Strength

lb/ft2

1 90 1 1.3:1 6.8E-9 1.61 25,396

2 90 15 1:1 1.0E-10 1.51 31,014

1 90 31 0.8:1 2.1E-9 1.76 166,391

3 90 40 0.8:1 1.0E-10 1.71 147,720

2 90 51 0.8:1 1.0E-10 1.76 147,970

3 90 52 0.9:1 1.3E-05 1.56 13,387

2 90 23 0.9:1 4.2E-06 1.61 27,004

2 30 42 1.3:1 6.0E-07

2 60 48 1.3:1 4.8E-07

1 90 53 1.3:1 1.2E-07 1.42 13,889

1 90 53 1.3:1 1.1E-07

3 90 73 1.3:1 3.5E-09 1.52 24,331

2 90 72 1.3:1 1.9E-08 1.50 22,639

2 60 60 1.3:1 1.2E-08

2 30 54 1.3:1 1.1E-07

* 1 = 100% industrial process water, * 2 = industrial and 80% FGD water, * 3 = 100% FGD water.

** Hydraulic Conductivity Procedure: ISO/TS 17892-11:2004 Geotechnical investigation and testing. Laboratory

testing of soil. Part 11: Determination of permeability by constant and falling head. (Hungarian version of the

European Technical Specification CEN ISO/TS 17892-11:2004, including Corrigendum CEN ISO/TS 17892-

11:2004/AC:2005).

Testing was performed on waste water, ash and samples of solidified ash from the Matra Power

Plant in Hungary. The dense slurry was comprised of the components shown in Table 7. The

ash compositions from Matra are shown in Table 8.

Table 7. Components of Dense Slurry from Matra Plant

Component Concentration (%)

Fly Ash 35.1

Coarse Fly Ash 10.5

Economizer Ash 2.5

Bottom Ash 4.3

Industrial Water 37.1

FGD Water 2.1

Lime Pre-Treatment (ion exchange)

Water

8.4
Page 9 of 11

Table 8. Matra Plant Average Ash Compositions

Oxide Fly Ash (wt%) Bottom Ash (wt%)

SiO2 45-49 90-92

CaO 7.5-9.5 0.2-0.8

MgO 4.5-5.2 0.1-0.2

Fe2O3 7.8-8.8 2-2.9

Al2O3 17.5-18.5 1-2

K2O 0.5-0.7 0.1-0.2

Na2O 0.2-0.3 --

SO3 5.5-6.5 0.1-0.2

The dense slurry was allowed to cure for 90 days after which it was analyzed for total metals and

leach performance using techniques similar to the Toxic Characteristic Leach Procedure (TCLP)

and the Simulated Precipitation Leach Procedure (SPLP). Table 9 shows the total metals

concentration of the solidified product and the leach performance using neutral and acidic

extraction water similar to the SPLP and TCLP tests respectively. Table 10 presents the

chemistry of the FGD water that was used to produce the dense slurry and Table 11 presents the

compressional strength and hydraulic conductivity of the cured Matra samples.

Table 9. Total Metals and Leach Performance of Matra Dense Slurry

As Ba Ca Cd Cr Cu Hg Mn Pb V

Total Metals mg/l

Min 34.1 52 53500 0.11 12.9 22.6 0.08 328 5.66 46

Max 39.2 93.5 57000 0.15 13.3 24.6 0.11 341 6.34 51

Av. 36.9 71.6 55770 0.14 13.17 23.63 0.093 336 6.06 48.8

Neutral Water Leach Test mg/l (SPLP)*

Min 0.092 0.06 490 0.0004 0.05** 0.02 0.001 0.02 0.005 0.005

Max 0.2 0.06 660 0.0004 0.05 0.02 0.001 0.02 0.005 0.008

Av. 0.14 0.06 587 0.0004 0.05 0.02 0.001 0.02 0.005 0.008

Acidic Leach Water mg/l (TCLP)*

Min 0.021 0.37 1920 0.0007 0.071 0.05 0.001 8.21 0.005 0.005

Max 0.112 0.44 2310 0.0011 0.106 0.06 0.001 10.2 0.005 0.005

Av. 0.069 0.4 2017 0.0009 0.089 0.057 0.001 8.88 0.005 0.005

* Leach tests indicated are similar to the SPLP and TCLP. Procedure used was MSZ 21979/1-1989. This procedure

has been revised and is now harmonized with the European Union. The new procedure numbers are: MSZ EN

12457-2-2003 (particle size <4mm) and MSZ EN 12457-4:2003 (particle size <10mm).

** Figures in bold font indicate element not detected at quantitation limits
Page 10 of 11

Table 10. FGD Water Analysis from the Matra Plant

Parameter Units Value

pH 6.5

Electrical Conductance (μS/cm) 56400

Evaporation Residue (mg/l) 74900

LOI of Evaporation

Residue

(%) 54.2

Chem. Oxygen Demand (mg/l) 1125

Sulfide (mg/l) 0.23

Sulfate (mg/l) 1100

Chloride (mg/l) 27100

Table 11. Matra Plant Solidified Dense Slurry Physical Properties

Sample No. Curing

Time

Hydraulic

Cond.

Comp.

Strength

Days cm/sec lb/ft2

Matra-30 30 2 X 10-4

--

Matra-60 60 7 X 10-5

5661

Matra-90 90 2.5X 10-4

7395

Matra-120 120 6 X 10-5

1065

Matra-150 150 4 X 10-5

4867

Matra-180 180 1X 10-4

11030

Table 12. Matra Impoundment Leachate Chemistry

Parameter Units Value

pH 8.2

Conductivity mS/cm 1.3

Evaporation Residue mg/l 1182

LOI of Evap. Residue Wt% 26.7

KOI mg/l <10

Sulfide mg/l <0.1

Sulfate mg/l 570

Chloride μg/l 82

Aluminum mg/l <0.25

Arsenic μg/l 1

Calcium μg/l 195

Cadmium μg/l <10

Chromium μg/l <50

Copper mg/l <0.02

Mercury μg/l <1

Manganese mg/l <0.02

Lead μg/l <100

Vanadium mg/l <0.25
Page 11 of 11

For more information, please contact:

Dale Timmons, R.G.

Program Manager, Business Development

NAES Corporation

Email: Dale.timmons@naes.com

Phone: 425-961-4700

Address: 1180 NW Main St.

Issaquah, WA 98027