ARTICLE IN PRESS

Available at www.sciencedirect.com

B I O S Y S T E M S E N G I N E E R I N G 1 0 0 ( 2 0 0 8 ) 4 0 1 – 4 0 8

1537-5110/$ - see frodoi:10.1016/j.biosys

�Corresponding auE-mail address:

journal homepage: www.elsevier.com/locate/issn/15375110

Research Paper: SE—Structures and Environment

Solid material retention and nutrient reduction propertiesof pervious concrete mixtures

Joe D. Lucka, Stephen R. Workmana,�, Mark S. Coyneb, Stephen F. Higginsa

aDepartment of Biosystems and Agricultural Engineering, University of Kentucky, 128 C.E. Barnhart Building, Lexington, KY 40546, USAbDepartment of Plant and Soil Sciences, University of Kentucky, Lexington, KY, USA

a r t i c l e i n f o

Article history:

Received 6 October 2007

Received in revised form

15 March 2008

Accepted 26 March 2008

Available online 3 June 2008

nt matter & 2008 IAgrE.temseng.2008.03.011

thor. Tel.: +1 859 257 3000;sworkman@bae.uky.edu

Runoff from agricultural activities can adversely affect the environment; however, little

research has been conducted to determine the performance of pervious concrete for use in

agriculture. Pervious concrete, with its unique infiltration properties, could be beneficial

when used as a solid/liquid separation material for animal feeding pads, manure, or

compost storage pads. Laboratory tests were conducted on replicated samples of pervious

concrete made from two aggregate sources (river gravel and limestone) with two size

fractions from each aggregate. Water was filtered through composted beef cattle manure

and bedding (compost) that was placed on top of the pervious concrete specimens. T-tests

indicated that the mass of compost retained on the surface of the pervious concrete

specimens was significantly greater when smaller aggregate sizes (#8 river gravel) were

used (p ¼ 0.012). Nutrient analyses were conducted on the effluent from the compost on

pervious concrete and compared to values from an identical test performed by filtering

water through compost on an 80 grade wire mesh screen. Filtering the compost effluent

through pervious concrete resulted in significant reductions in total nitrogen, soluble

phosphorus, and total phosphorus compared to the wire screen; however, no consistently

significant differences were found with respect to the other analytes (e.g. dissolved organic

carbon, ammonium, nitrate, and nitrite). The use of different aggregate types (river gravel

or limestone) or different additives (fly ash or fibres) did not have any significant effect on

analyte levels. This suggests that combinations of these materials in pervious concrete

mixtures will not affect the performance of pervious concrete in this type of application.

& 2008 IAgrE. Published by Elsevier Ltd. All rights reserved.

1. Introduction

The United States Environmental Protection Agency (USEPA)

has identified siltation, pathogens, and nutrients as the top

three pollutants in impaired rivers and streams (USEPA, 2000).

Siltation or sedimentation affected nearly 40% of the rivers

and streams identified as impaired. Siltation, usually consist-

ing of silt or clay particles, can degrade habitat for aquatic life

and ultimately change the hydraulic properties of the affected

Published by Elsevier Ltd.

fax: +1 859 257 5671.(S.R. Workman).

stream (USEPA, 2000). Sediments entering a stream environ-

ment can transport nutrients, pathogens, and toxic sub-

stances (USDA-NRCS, 1997). Nutrient pollution affects 30% of

rivers and streams identified as impaired. Nitrogen (N) and

phosphorus (P) are the two nutrients that contribute most to

water quality degradation. Nutrient pollution in surface

waters can be detrimental to most forms of aquatic life.

Increased N and P promotes eutrophication, a process in

which aquatic plants and algae decompose resulting in the

All rights reserved.

ARTICLE IN PRESS

B I O S Y S T E M S E N G I N E E R I N G 1 0 0 ( 2 0 0 8 ) 4 0 1 – 4 0 8402

depletion of dissolved oxygen, in rivers, streams, lakes, and

ponds, and the growth of toxic cyanobacteria. Eutrophication

is the leading water quality problem in the United States

(USEPA, 1996). Therefore, erosion control and wastewater

treatment in agricultural areas can have a significant

beneficial effect on surface water quality.

Livestock manure can be a significant source of N and P

where large confined animal feeding operations are located

(USEPA, 2000; USDA-NRCS, 1997). Reducing particles and

nutrients in runoff from animal production facilities reduces

the likelihood of impairing streams and other water bodies.

Various measures have been developed to treat these

effluents. For example, settling basins have been introduced

to capture runoff from rainfall events, provide solid/liquid

separation, and discharge the runoff at lower velocities. Two

types of basins, continuous flow and batch flow, have been

studied for use in controlling animal facility runoff (Gilbert-

son et al., 1971). Large basins are typically required for

adequate capacity, and the long detention times that are

necessary for particle separation; typical minimum detention

times of 1–2 h are recommended (Gilbertson et al., 1972;

Moore et al., 1975). Filter materials for solid/liquid separation

have also been tested for use in settlement basins and include

perforated risers, rock, expanded metal, slatted boards, and

concrete lipped weirs (Gilbertson et al., 1971; Cramer et al.,

1976; Nye and Jones, 1980). Porous dams constructed of

graded stone and treated wood have been tested; however,

clogging of the dam systems led to their failure (Cramer et al.,

1976). Expanded metal screens were tested to determine their

effectiveness at solid/liquid separation; however, solid parti-

cles were not effectively filtered by the screens (Cramer

et al., 1976).

The main objectives of the aforementioned treatment

practices were to control site runoff, remove excessive

nutrients, and eliminate solids from wastewater by capturing

and treating the runoff volume. These treatment practices

have produced positive results in terms of pollutant reduction

in wastewater and runoff from animal production facilities

(Gilbertson et al., 1971; Cramer et al., 1976; Nye and Jones,

1980). Thus, effective solid–liquid separation can be beneficial

in treating effluents because chemicals, nutrients, and

pathogens can adsorb to solid particles in the wastewater

stream (USDA-NRCS, 1997). However, further improvement of

these treatment practices will be necessary to provide more

efficient and economical methods for reducing pollutants in

the natural environment.

Pervious concrete is made by eliminating the fine aggregate

from a typical concrete mixture which allows for rapid water

infiltration (Ghafoori and Dutta, 1995a). It has proven very

useful in controlling storm water runoff and reducing the

need for retention ponds in urban areas where space for these

structures can be limiting (Tennis et al., 2004). Pervious paving

techniques have been beneficial in various non-roadway

surface projects (Ghafoori and Dutta, 1995b; Tennis et al.,

2004). For example, pervious concrete has been used to

construct greenhouse floor systems. Benefits from pervious

concrete greenhouse floors include reduction and filtration of

ponded water while providing durable surfaces for moving

equipment (Herod, 1981). Runoff containing nutrients and

solid particles from greenhouses can be harmful to the

surrounding water resources. Pervious greenhouse floors

allow water to be captured and discharged to designated

treatment or bioremediation areas. Other applications where

pervious concrete has shown promise include car parks,

sidewalks, and pavement edge drains (Tennis et al., 2004).

Pervious concrete, with its unique interconnected void

structure, could be a promising component in the treatment

of wastewater from animal production facilities by separating

the solids from liquids on site rather than collecting all of the

material in the runoff. A recent study evaluated the hydro-

logic properties of pervious concrete (Luck et al., 2006). The

pervious concrete was found to be effective at trapping solid

particles as water filtered through composted beef cattle

manure and bedding. However, adding compost to the surface

significantly decreased the permeability of the pervious

concrete, with overall reductions ranging from 20% to 50%

(Luck et al., 2006).

Controlling runoff containing sediments and nutrients

from animal production facilities is necessary to prevent

pollution of surface waters. Identifying new methods of

treating effluent from agricultural areas will be necessary as

environmental protection standards become more stringent.

Pervious concrete could provide environmental benefits when

used for animal feeding pads, manure storage pads, or

flooring systems in animal buildings. The specific goals of

this research were to: (i) evaluate the ability of pervious

concrete to filter solid particles and material from composted

beef manure and bedding; (ii) determine whether different

aggregates or additives used in pervious concrete mixtures

affected material retention or effluent analyte concentra-

tions; and (iii) compare the nutrient reduction capacity of

pervious concrete relative to a non-reactive 80 grade wire

mesh screen.

2. Materials and methods

2.1. Test materials

The pervious concrete specimens used for testing were 0.45 m

in length and width with a thickness of 140 mm. Sixteen

mixtures were created from four aggregate sizes while

varying the use of fibres and fly ash in the pervious concrete.

Each of the mixtures received 90 kg of water, 4.4 g of an air-

entraining admixture, and 0.93 g of a retarding admixture per

100 kg of cementitious material (cement or cement plus fly

ash). The proportions of materials in each of the sixteen mix

designs are presented in Table 1. The D50 (particle size

corresponding to 50% passing) for the aggregates used in

the pervious concrete mixtures were: 6.9 mm, #8 river gravel;

11.0 mm, #57 river gravel; 12.1 mm, #9 limestone; and

13.7 mm, #57 limestone. The coefficients of uniformity (Cu)

for the aggregates were: 15, #8 river gravel; 3, #57 river gravel;

5, #9 limestone; 2, #57 limestone. A Cu value less than 4

indicates a well-sorted (narrow particle size distribution)

aggregate, while a Cu greater than 6 indicates a poorly sorted

(wide particle size distribution) aggregate. Three replicates

were made for each mixture giving a total of 48 specimens.

A 0.25 m3 concrete mixer was used for batching, and the

pervious concrete was placed by hand in wooden forms in

ARTICLE IN PRESS

Table 1 – Pervious concrete specimen mix design proportionsa

Pervious concrete mixdesigns

Coarse aggregate(1227.3 kg)

Cement(272.2 kg)

Cement(227.3 kg)

Fly ash class F(45.5 kg)

Fiber(0.45 kg)

1–4 #8 River Gravel 1,2 3,4 3,4 2,3

5–8 #57 River Gravel 5,6 7,8 7,8 5,7

9–12 #9 Limestone 9,10 11,12 11,12 9,11

13–16 #57 Limestone 13,14 15,16 15,16 13,15

a The mixture identification is listed below each component.

Table 2 – T-tests for effects of aggregate type on compostretention

Aggregatetype

Mean compost retained on specimensurface (%)

#8 River

Gravel

97.2a

#57

Limestone

94.3b

#57 River

Gravel

93.9b

#9 Limestone 92.8b

Note: Mean values with different superscript letters are signifi-

cantly different (pp0.05).

B I O S Y S T E M S E N G I N E E R I N G 1 0 0 ( 2 0 0 8 ) 4 0 1 – 4 0 8 403

one lift, struck off 15 mm above the final compacted height of

140 mm, and compacted using a steel hand roller 45 kg in

weight and 1 m in width. The compaction of the specimens

was stopped when the final height of 140 mm was achieved.

The total compaction (based on the initial and final specimen

thickness) is approximately 10%. Once compaction of the

specimens was complete, they were covered with plastic and

cured for 28 days.

Composted beef cattle manure and wood shavings bedding

(compost) were used as the material to evaluate solid/liquid

separation efficiency because it provided similar particle

sizes of manure and bedding associated with typical beef

cattle and dairy operations, without the accompanying

pathogens and odour. The amount of compost added

(0.125 kg wet weight) was designed to produce a depth

(approximately 25 mm) of material on the surface of the

pervious concrete.

2.2. Test methods

2.2.1. Solid/liquid separation testingFour hollow cylinders constructed of schedule 40 PVC pipe

(100 mm internal diameter, 100 mm height) were placed on

the specimens. Each cylinder was filled with a known mass

(kg oven-dry weight) of compost. The four cylinders limited

the contact area between the compost and specimen to

0.031 m2 or approximately 15% of the total surface area. One

litre of water was poured into each cylinder which filtered

through the compost and pervious concrete. This amount of

water was sufficient to ensure enough effluent would be

collected for later analyses. The time required for the

litre of water to completely drain through the compost and

pervious concrete was less than 15 min. The cylinders were

then left undisturbed overnight and 24 h after the initial pour,

another litre of water was poured into each of the cylinders.

The total 2 l of water corresponds to a depth of 254 mm in

accumulated rainfall, based on the area of the cylinders,

approximately 20% of the average yearly accumulated rainfall

for Kentucky (NOAA, 2007). The compost remaining in each

cylinder was removed by sliding a thin sheet of metal

between the cylinder and the surface of the specimen. This

ensured that the compost would not be pressed into the

specimen or exposed to the surface of the specimen outside

the cylinder. The compost recovered was oven-dried at 105 1C

for 24 h and the oven-dry weight was recorded. The difference

between the oven-dry weight of compost added to the

specimen and the oven-dry weight of compost removed from

the specimen was used to calculate the percentage of

compost retained on the surface. The percentage of compost

retained on the surface represents the amount of compost

that was recovered by the scraping method and can be found

in Table 2.

2.2.2. Effluent testingDuring the solid/liquid separation testing (described above),

one of the four cylinders placed on each specimen was used

for effluent collection. The effluent from this cylinder was

captured and weighed after the litre of water was filtered

through the compost and pervious concrete on day one and

day two. The effluent was tested for: pH, electrical conduc-

tivity (EC), 5-day biochemical oxygen demand (BOD), dis-

solved organic carbon (DOC), ammonium (NH4+), nitrate (NO3

�),

nitrite (NO2�), total nitrogen (TN), soluble phosphorus (SP), and

total phosphorus (TP). The concentrations of the analytes

(mg l�1) were multiplied by the total volume of effluent

recovered to determine the total mass (mg) passing through

the specimen. These values were divided by the mass of

compost added to each cylinder (oven-dried weight) to

determine the amount (mg kg�1 compost) of each nutrient

passing through the pervious concrete specimens. The water

filtration/effluent collection process (described above in solid/

liquid separation testing and effluent testing) was also

performed on three consecutive days with four cylinders

and compost placed on a non-reactive 80 grade wire mesh

screen. This test was used to compare the effect of pervious

concrete on effluent properties compared to the wire screen.

The effluent from the compost filtered through the wire

ARTICLE IN PRESS

B I O S Y S T E M S E N G I N E E R I N G 1 0 0 ( 2 0 0 8 ) 4 0 1 – 4 0 8404

screen was tested for: pH, EC, DOC, NH4+, NO3

�, NO2�, TN, SP,

and TP. All analyses were performed in accordance with the

Standard Methods for the Examination of Water and Wastewater

20th edn. (APHA, 1998).

2.3. Statistical analysis

If the experimental results from the solid/liquid separation

and effluent testing were normally distributed, the statistical

analysis proceeded in SASs (SAS Institute, 1999) using a

generalized linear model to test for treatment effects

(aggregate or additive type). If the results were not normally

distributed, a mixed model (SAS Institute, 1999) was used to

test for treatment effects. T-tests were conducted to deter-

mine whether aggregate (#8 river gravel, #57 river gravel, #9

limestone, or #57 limestone) or additive (cement, cement with

fly ash, cement with fibre, or cement with fly ash and fibre)

resulted in significant differences in the effluent analyses and

in the amount of compost retained on the surface of the

specimens. T-tests were also utilized to determine whether

there were significant differences in effluent pH, EC, DOC,

NH4+, NO3

�, NO2�, TN, SP, or TP levels based on the filtration

method (pervious concrete versus wire screen). The t-tests

were conducted using the two-tailed least significant differ-

ence (LSD) and differences were considered significant at an

alpha value equal to 0.05 (pp0.05) (Montgomery, 1997).

Significant differences in daily effluent levels from leaching

events for the pervious concrete and wire screen were

evaluated based on effluent data from all specimens for each

day. This analysis was performed using a mixed model to test

for the effects of repeated measures in SASs using PROC

MIXED (SAS Institute, 1999). Differences in the mean daily

effects were considered significant at pp0.05 (Montgomery,

1997).

3. Experimental results and discussion

3.1. Solid/liquid separation

The mean amounts of compost retained ranged from 92.8%

for the #9 limestone to 97.2% for the #8 river gravel. There

were significant differences among the aggregate types

(pp0.05). Significantly more compost was retained on the

surface of the specimens made with #8 river gravel aggregate

compared to all other aggregate types (Table 2). There were no

significant differences among the remaining three aggregate

types with respect to the amount of compost retained. The

use of different additives did not have a significant effect on

compost retention. Overall, the pervious concrete was

effective in separating liquid and solids. For all aggregate

types less than 8% of the compost moved into the concrete

matrix after the total 2 l of water was applied (Table 2).

Negligible amounts of solid material passed through the

pervious concrete specimens.

The specimens made with #8 river gravel stood out as the

best aggregate type for retaining compost material on the

surface of the specimens for later removal. The relationship

between particle size and pore size in soils has been well

documented. In porous media, increasing the particle size

typically yields increased individual pore sizes (Sylvia et al.,

1999). Similarly, the #8 river gravel aggregate consisted of a

much smaller particle size (D50 of 6.9 mm) than the other

three aggregates which may have contributed to smaller

pores at the surface and therefore less compost penetration

into the specimens. There were no significant differences in

the amount of compost retained between the specimens

made with #57 river gravel, #9 limestone, or #57 limestone.

The individual pore sizes in the specimens made from these

aggregates were likely greater than the pores in the #8 river

gravel which explains the greater amount of compost

material moving into the pervious concrete surface. The D50

particle sizes for these three aggregates (ranging from 11.0 to

13.7 mm) were similar which supports the finding of no

significant difference in compost retention among these three

aggregate types. The surface of pervious concrete has been

identified as a problem area in terms of maintenance. The top

portion of pervious concrete slabs has been found to have the

lowest porosity after a placement process with approximately

10% surface compaction (Haselbach and Freeman, 2006). The

specimens used in this test had a compaction of approxi-

mately 10% based on the initial and the final specimen height

after compaction. The previous research by Haselbach and

Freeman (2006) indicated that porosity throughout the

pervious concrete ranged from lowest at the top to highest

at the bottom, which was a result of surface compaction.

Therefore, for maintenance purposes, it could be advanta-

geous to use smaller aggregates where controlling the

amount of material moving into the surface could be critical

for maintaining porosity.

3.2. Effluent testing

The analysis of the compost effluent filtered through the wire

screen indicated that for most of the analytes, the maximum

concentration occurred on day three. The exceptions were

NO3�, with a maximum concentration on day one, and NO2

�,

with a maximum concentration on day two. During the wire

screen effluent analysis, significant concentration increases

(pp0.05) were found from day one to day two for EC, DOC,

NH4+, NO2

�, TN, and SP.

Significant increases in concentration were found in the

effluent from the compost on the pervious concrete for BOD,

EC, DOC, TN, SP, and TP (pp0.05) from day one to day two

(Table 3). Ammonia, NO3�, and NO2

� concentrations also

increased from day one to day two; however, these increases

were not significant. There were some significant differences

detected among analyte concentrations based on the aggre-

gates and additives used in the pervious concrete. No

consistent differences were found; therefore, it was not

possible to determine whether the aggregates or additives

resulted in a significant difference in the analytes. Previous

testing on the specimens indicated high permeability rates

(ranging from 7 to 14 l s�1 m�2) that were independent of the

aggregate types used in the pervious concrete mixtures (Luck

et al., 2006). It is feasible that the permeability of the

specimens did not allow for much interaction between the

compost effluent and the concrete. Using different aggregate

types (river gravel or limestone) or additives (fly ash or fibre)

did not appear to significantly affect effluent nutrient

ARTICLE IN PRESS

Table 3 – Mean concentration or value of pH, EC, BOD,DOC, NH4

+, NO3�, NO2

�, TN, SP, and TP in effluent frompervious concrete (PC) or wire screen (WS) during twoconsecutive leaching events

Analyte Filtration method Day 1 Day 2

pH (units) PC 9.3a 9.3a

WS 7.7b 7.7b

EC (mmho cm�1) PC 1067 A 1350 B

WS 1170 A 1322.5 B

BOD (mg l�1) PC 38.7 A 42.5 B

WS – –

DOC (mg kg�1) PC 710.0 A 1105.0 B

WS 880.0 A 1192.0 B

NH4+ (mg kg�1) PC 23.7 48.4

WS 13.3 A 32.6 B

NO3� (mg kg�1) PC 13.6 16.5a

WS 5.4 4.3b

NO2� (mg kg�1) PC 1.4a 1.8

WS 0.3b A 3.0 B

TN (mg kg�1) PC 65.7a A 163.7a B

WS 123.9b A 319.5b B

SP (mg kg�1) PC 2.0a A 8.1a B

WS 12.4b A 16.3b B

TP (mg kg�1) PC 6.7a A 21.1a B

WS 22.0b 38.0b

Different lower-case letters between treatment means (PC or WS)

indicate significant differences (pp0.05).Different capital letters

indicate a significant difference in analyte levels between leaching

events (pp0.05).

B I O S Y S T E M S E N G I N E E R I N G 1 0 0 ( 2 0 0 8 ) 4 0 1 – 4 0 8 405

concentrations from compost material placed on pervious

concrete.

There was a significant increase (po0.05) in pH on day one

and day two as a result of filtering the effluent through the

pervious concrete compared to the wire mesh screen (Table 3).

Previous research on the buffering effects of permeable

pavement sub grades has indicated that as water percolates

through the gravel base material, the pH increases (James and

Shahnin, 1998; Collins, 2007). The pervious concrete speci-

mens used for testing were relatively new and had not been

subjected to any extended periods of saturation. Filtering the

compost effluent through the higher alkaline environment of

the pervious concrete resulted in a significant increase in

effluent pH compared to the wire screen. This agrees with

previous research conducted on multiple permeable pave-

ments over gravel sub grades where effluent from the

pervious concrete installations typically returned the highest

pH (Collins, 2007). Alkalinity of an environment can be an

important factor in N transformations. For instance, NO2�

(an intermediate in the conversion of NH4+ to NO3

�)-oxidizing

bacteria can be suppressed as pH levels increase above nine

in a soil environment (Pearce et al., 1998; Coyne, 1999). This

can result in an overall decrease in NO3� production until the

pH of the system becomes more neutral and these bacteria

become more active.

Electrical conductivity indicates solute concentrations in

the effluent filtered with pervious concrete and the wire

screen. The statistical analysis indicated no significant

difference in EC levels between the two filtering methods

(Table 3). Less DOC (mg kg�1) was recovered in the effluent

filtered from the pervious concrete compared to the wire

screen; however, there were no significant differences in DOC

between the two filtering methods on either day (Table 3).

The use of different aggregate types (limestone or river gravel)

or additives (fly ash or fibre) did not have a significant effect

on EC or DOC levels in the effluent from the pervious

concrete.

The BOD in the compost effluent filtered through the

pervious concrete specimens ranged from 15.5 to 47.4 mg l�1

on day one and from 27.4 to 46.7 mg l�1on day two (analysis

not performed on effluent from wire screen). Typically, the

BOD concentration in discharge from a wastewater treatment

facility is limited to 30 mg l�1. Although some of the pervious

concrete specimens yielded values of BOD below 30 mg l�1,

the average values for days one and two, 38.7 mg l�1and

42.5 mg l�1, respectively, exceeded the allowable limit. It is

reasonable to conclude that the discharge from solid/liquid

separation applications of pervious concrete with this form of

compost would require additional treatment.

The benefits of filtration using pervious concrete were not

consistent in terms of N reduction. The analyses for NH4+,

NO3�, and NO2

� yielded results that were typically higher for

the pervious concrete effluent compared to the wire screen.

Day two NO3� and day one NO2

� levels were the only

measurements that were significantly higher for the pervious

concrete. Filtration using pervious concrete had a significant

impact on lowering TN levels in the compost effluent as TN

levels were significantly lower on days one and two compared

to the wire screen (Fig. 1). This is potentially due to better

particulate trapping with the pervious concrete compared to

the wire screen, which can reduce nutrient loads in waste-

water (USDA-NRCS, 1997). Previous research studied pervious

concrete for the potential removal of TN and concluded that

the pervious concrete was capable of reducing TN levels over

several days (Sung-Bum and Mang, 2004). The mechanism

responsible for reducing TN was believed to be due to

microorganisms attached to the pervious concrete.

Filtration using the pervious concrete resulted in signifi-

cantly less SP and TP compared to the wire screen (Fig. 2).

Sung-Bum and Mang (2004) indicated that pervious concrete

has the potential for removing TP from water, which was

attributed to microbial activity within the pervious concrete.

Previous research has indicated that the availability of

calcium (Ca) oxides or magnesium (Mg) carbonate in the

finished concrete may have contributed to increased pH

(Collins, 2007). Given that the specimens used during testing

were not highly leached, it is reasonable to assume that there

were higher amounts of these compounds available for

leaching. In higher pH soil environments, the addition of Ca

and Mg can result in the precipitation of P as Ca phosphates

or Mg phosphates (Lindsay, 1979). This may be another

explanation for the decrease in SP from the pervious concrete

as available SP was precipitated as Ca or Mg phosphates. The

ARTICLE IN PRESS

0.0

2.0

4.0

6.0

8.0

10.0

12.0

321

Day

Cum

ulat

ive

Am

ount

of A

naly

te in

Eff

luen

t (m

g)

NH4+ (x 10-1)

NH4+ (x 10-1)

NO3-

NO2-

NO3-

NO2-

TN (x 10-1)

TN (x 10-1)

(Solid lines represent effluent from wire screen, dashed lines represent

effluent from pervious concrete)

Fig. 1 – Transport of NH4+, NO3

�, NO2�, and TN from compost through pervious concrete and wire screen.

0.0

2.0

4.0

6.0

8.0

10.0

12.0

321

Day

Cum

ulat

ive

Am

ount

of A

naly

te in

Eff

luen

t (m

g)

DOC (x 10-2)

DOC (x 10-2)

SP

TP (x 10-1)

SP

TP (x 10-1)

(Solid lines represent effluent from wire screen, dashed lines represent

effluent from pervious concrete)

Fig. 2 – Transport of DOC, SP, and TP from compost through pervious concrete and wire screen.

B I O S Y S T E M S E N G I N E E R I N G 1 0 0 ( 2 0 0 8 ) 4 0 1 – 4 0 8406

implication here is that as the pervious concrete ages, the

available Ca and Mg would most likely decrease. This would

result in a lower buffering capacity of the pervious concrete,

which would in turn lower the ability of the system to

precipitate SP as an insoluble form such as Ca or Mg

phosphate.

The addition of amendments to manure has been found to

reduce SP concentrations in manure effluent (Moore et al.,

2006). Adding calcium and/or class C fly ash, for instance, can

reduce SP levels in animal manure (Moore and Miller, 1994).

The difference between class C fly ash and the class F fly ash

used in these pervious concrete specimens is the amount of

total calcium. Class C fly ash can contain between 30% and

40% calcium, whereas class F fly ash typically ranges between

1% and 12% (McKerall et al., 1982). The availability of calcium

and class F fly ash in the pervious concrete may have

contributed to lower SP levels when compared to the wire

screen. However, comparing pervious concrete mixtures

made with or without the addition of fly ash resulted in no

consistently significant differences among the specimens.

Therefore, substituting class F fly ash for cement in this case

resulted in no significant effect.

ARTICLE IN PRESS

B I O S Y S T E M S E N G I N E E R I N G 1 0 0 ( 2 0 0 8 ) 4 0 1 – 4 0 8 407

Past research has focused on the removal of solid particles

as a method for reducing overall nutrient loads in effluent

from animal waste and bedding (Meyer et al., 2004, 2007).

Studies have indicated that higher solid particle removal

efficiency leads to lower nutrient levels (Meyer et al., 2007).

This may be an indication that the pervious concrete was able

to provide more adequate solid particle separation than the

wire screen. Another possible cause for reduced analytes in

the effluent from the pervious concrete could be absorption or

specific retention of effluent within the specimens. Specific

retention represents the portion of the total porosity that

does not readily drain due to gravity drainage after saturated

conditions have been reached (Luck et al., 2006). The pervious

concrete specimens used during this set of experiments were

tested to determine specific retention (ranging from 4.5% to

7.5%) in an earlier study (Luck et al., 2006). As a result, less

total effluent was collected from the pervious concrete

specimens (655 and 732 ml on days one and two, respectively)

compared to the wire screen (914 ml on both days). Analyte

concentrations were multiplied by the total volume of

effluent collected to determine the total mass (mg) of each

analyte that passed through the pervious concrete or wire

screen. Therefore, pervious concrete could reduce the total

amounts of pollutants by absorbing effluent as it is passes

through the concrete pores. As previously discussed, pervious

concrete porosity decreases from the top of the slab to the

bottom as a result of surface compaction (Haselbach and

Freeman, 2006). The distribution of effluent absorption was

not tested during this project; however, it is possible that the

lower porosity near the surface could lead to higher absorp-

tion as a result of increased surface area and smaller pores in

this region.

4. Conclusions

The pervious concrete was effective at solid/liquid separation

by retaining the solid material as water was passed through

the compost and pervious concrete specimens. The speci-

mens retained 92–97% of the solid material, which could be

removed from the surface of the pervious concrete. Speci-

mens consisting of #8 river gravel retained significantly more

compost on the surface for removal. The #8 river gravel,

which was considerably smaller than the other aggregates

used, is believed to have provided smaller pore sizes which

allowed less compost to penetrate the surface of the speci-

mens. Use of smaller aggregates sizes in pervious concrete

could provide benefits in terms of maintenance and debris

removal as a result of this.

TN, SP, and TP were at significantly lower levels (mg kg�1

compost) on both days when filtered through the pervious

concrete. SP reduction may have occurred due to available Ca

or Mg in the pervious concrete which, given the higher pH,

could have allowed P to precipitate as Ca or Mg phosphates

instead of SP. Another mechanism responsible for the

reduction of analytes in the effluent could also be due to

absorption or retention of effluent water in the pervious

concrete. The pervious concrete was able to absorb effluent

water from the compost, which may have been a major factor

in the reduction of total nutrient loads from the system.

Based on these data, pervious concrete could provide a

method for trapping nutrients from rainfall events when

compared to compost material stacked on a typical concrete

pad, which would not provide any absorption after a rainfall

event.

Different aggregate types (river gravel or limestone), aggre-

gate sizes (#8s, #9s, or #57s), or additives (fibre or fly ash) do

not significantly affect effluent nutrient levels from solid

compost material stacked on pervious concrete. The results

are useful in evaluating the economics of pervious concrete

mixtures utilized in different applications. Readily available

aggregate types and sizes can vary by geographic region and

can therefore affect the cost of pervious concrete. Similarly,

fly ash is a material that is commonly added to concrete

mixtures as a cost-effective replacement for Portland cement.

The addition of fibre to a concrete mixture is a common

practice for increasing strength so that the concrete will not

fail under increased loadings. Varying these mixture compo-

nents does not appear to affect the solid/liquid separation

performance of pervious concrete in an application of this

nature.

Acknowledgements

Successful completion of all laboratory tests would not have

been possible without the technical assistance of Tiffany

Graham, Laura Steinmetz, Ann Freytag, Kelly Silva, Josiane

Oliveira, Tami Smith, and Jim Crutchfield. This project was

completed with assistance from the Kentucky Ready Mixed

Concrete Association and funding from the Portland Cement

Association. The authors would also like to acknowledge the

support and collaboration of the Department of the Interior,

US Geological Survey and the University of Kentucky Re-

search Foundation, under Grant Number 06HQGR0087.

The information reported in this paper (No. 07-05-003) is

part of a project of the Kentucky Agricultural Experiment

Station and is published with the approval of the Director.

This manuscript is submitted for publication with the

understanding that the United States Government is author-

ized to reproduce and distribute reprints for governmental

purposes. The views and conclusions contained in this

document are those of the authors and should not be

interpreted as necessarily representing the official policies,

either expressed or implied, of the US Government.

R E F E R E N C E S

APHA (American Public Health Association) (1998). StandardMethods for the Examination of Water and Wastewater, 20thedn. American Public Health Association, American WaterWorks Association, and Water Environment Federation, Wa-shington, DC

Collins K A (2007). A field evaluation of four types of permeablepavement with respect to water quality improvement andflood control. MS Thesis. Raleigh, NC. North Carolina StateUniversity, Department of Biological and Agricultural Engi-neering.

Coyne M S (1999). Soil Microbiology: An Exploratory Approach.Delmar Publishers, Albany, NY

ARTICLE IN PRESS

B I O S Y S T E M S E N G I N E E R I N G 1 0 0 ( 2 0 0 8 ) 4 0 1 – 4 0 8408

Cramer C O; Converse J C; Brevik T J; Tenpas G H; Schlough D A(1976). Runoff control-systems for paved dairy-cattle yards—

case studies. Transactions of the ASAE, 19(1), 114–118Ghafoori N D; Dutta S (1995a). Development of no-fines concrete

pavement applications. Journal of Transportation Engineering,121(3), 283–288

Ghafoori N D; Dutta S (1995b). Building and nonpavementapplications of no-fines concrete. Journal of Materials in CivilEngineering, 7(4), 286–289

Gilbertson C B; McCalla T M; Ellis J R; Woods W R (1971). Methodsof removing settleable solids from outdoor beef-cattle feedlotrunoff. Transactions of the ASAE, 14(5), 899

Gilbertson C B; McCalla T M; Ellis J R; Woods W R (1972). Beefcattle feedlot runoff, solids transport and settling character-istics. Transactions of the ASAE, 15(6), 1132–1134

Haselbach L M; Freeman R M (2006). Vertical porosity distribu-tions in pervious concrete pavement. ACI Materials Journal,103(6), 452–458

Herod S (1981). Porous concrete market blooms in greenhouse.Modern Concrete, January, 40–44

James W; Shahnin R (1998). Pollutants leached from pavementsby acid rain. Advances in Modeling Management of Storm-water Impacts, 6, 321–349

Lindsay W L (1979). Chemical Equilibrium in Soils. Wiley,New York

Luck J D; Workman S R; Higgins S F; Coyne M S (2006). Hydrologicproperties of pervious concrete. Transactions of the ASAE,49(6), 1807–1813

McKerall W C; Ledbetter W B; Teague D J (1982). Analysis of flyashes produced in Texas. Research Report No. 240-1, TexasTransportation Institute, Texas A&M University, College Sta-tion, Texas.

Meyer D; Harner J P; Tooman E E; Collar C (2004). Evaluation ofweeping wall efficiency of solid liquid separation. AppliedEngineering in Agriculture, 23(1), 113–117

Meyer D; Ristow P L; Lie M (2007). Particle size and nutrientdistribution in fresh dairy manure. Applied Engineering inAgriculture, 20(3), 349–354

Montgomery D C (1997). Design and Analysis of Experiments.Wiley, New York

Moore J A; Hegg R O; Scholz D C; Strauman E (1975). Settling solidsin animal waste slurries. Transactions of the ASAE, 18, 694–698

Moore Jr. P A; Joern B C; Edwards D R; Wood C W; Daniel T C(2006). Effects of manure amendments on environmental andproduction problems. In: Animal Agricultural Environment:National Center for Manure and Animal Waste Management.White Papers. 2006. St. Joseph, MI: ASABE (Rice J M; Caldwell DF; Humenik F J, eds), pp 759–776

Moore Jr. P A; Miller D M (1994). Decreasing phosphorus solubilityin poultry litter with aluminum, calcium, and iron amend-ments. Journal of Environmental Quality, 23, 325–330

NOAA (National Oceanic and Atmospheric Administration) (2007).Point Precipitation Frequency Estimates from NOAA Atlas 14,Lexington WSO Airport, Kentucky Available at/www.hdsc.nws.noaa.govS Accessed 30 October 2007

Nye J C; Jones D D (1980). Experiences with runoff control systemsin Indiana. Transactions of the ASAE, 23(6), 1409–1412

Pearce R C; Zhan Y; Coyne M S (1998). Nitrogen transformations inthe tobacco float system. Tobacco Science, 42, 82–88

SAS Institute (1999). SAS/STAT User’s Guide Version 9.1. SASInstitute Inc., Cary, NC Available at /http://support.sas.com/91doc/docmainpage.jspS Accessed 16 August 2006

Sung-Bum P; Mang T (2004). An experimental study on the water-purification properties of porous concrete. Cement and Con-crete Research, 34, 177–184

Sylvia D M; Fuhrmann J J; Hartel P G; Zuberer D A (1999).Principles and Applications of Soil Microbiology, 2nd edn.Pearson Education, Inc., Upper Saddle River, NJ

Tennis P D; Leming M L; Akers D J (2004). Pervious ConcretePavements EB302, Portland Cement Association. Skokie,Illinois, and National Ready Mixed Concrete Association.Silver Spring, MD, USA

USDA-NRCS (US Department of Agriculture-Natural ResourcesConservation Service) (1997). Water quality and agri-culture: status, conditions, and trends, Working Paper #16.Washington, DC.

USEPA (US Environmental Protection Agency) (1996). Environ-mental indicators of water quality in the United States EPA841-$-96-002, US Environmental Protection Agency, Office ofWater (4503F). US Government Printing Office, Washington, DC

USEPA (US Environmental Protection Agency) (2000). NationalWater Quality Inventory Report to Congress (305b Report): 2000Water Quality Report. Available at: /http://www.epa.govS.Accessed on March 16, 2006.