ASTM D6249-98(2004)

Standard Guide for Alkaline Stabilization of Wastewater Treatment Plant Residuals

SCOPE
1.1 This document provides guidance for use of reactive alkaline materials (quicklime, hydrated lime, high lime fly ash, or other byproducts) for treating wastewater solids (biosolids) to reduce pathogen levels and achieve compliance with regulatory requirements. Federal (40 CFR, Part 503) regulations for use or disposal of biosolids became effective on March 22, 1993; refer to USEPA regulations and guidance documents for information on other treatment processes or for specific requirements for use or disposal of biosolids.  
1.2 Additional requirements may be imposed by individual states, and these are available through state regulatory agencies that issue permits for treatment and use or disposal, or both, of biosolids.

General Information

• Status: Historical
• Publication Date: 09-Apr-1998
• ICS: 13.060.30 - Sewage water
• Technical Committee: C07 - Lime and Limestone
• Drafting Committee: C07.02 - Specifications and Guidelines

Relations

• Replaces: ASTM D6249-98 - Standard Guide for Aklaline Stabilization of Wastewater Treatment Plant Residuals
• Effective Date: 10-Apr-1998
• Replaced By: ASTM D6249-06 - Standard Guide for Alkaline Stabilization of Wastewater Treatment Plant Residuals
• Effective Date: 01-Jun-2006
• Referred By: ASTM C1529-19 - Standard Specification for Quicklime, Hydrated Lime, and Limestone for Environmental Uses
• Effective Date: 10-Apr-1998
• Referred By: ASTM C911-19 - Standard Specification for Quicklime, Hydrated Lime, and Limestone for Selected Chemical and Industrial Uses
• Effective Date: 10-Apr-1998
• Referred By: ASTM D5050-08(2023) - Standard Guide for Commercial Use of Lime Kiln Dusts and Portland Cement Kiln Dusts
• Effective Date: 10-Apr-1998

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D6249–98 (Reapproved2004)
Standard Guide for
Alkaline Stabilization of Wastewater Treatment Plant
Residuals
This standard is issued under the fixed designation D 6249; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.2 PSRP—Processes to Significantly Reduce Pathogens
(equivalent to 503 Class B).
1.1 This document provides guidance for use of reactive
alkaline materials (quicklime, hydrated lime, high lime fly ash,
4. Significance and Use
or other byproducts) for treating wastewater solids (biosolids)
4.1 Operators of power and other plants producing alkaline
to reduce pathogen levels and achieve compliance with regu-
by-products and wastewater treatment plant operators needing
latoryrequirements.Federal(40CFR,Part503)regulationsfor
to treat and manage wastewater solids will find this guide
use or disposal of biosolids became effective on March 22,
helpful in dealing with their materials.
1993; refer to USEPAregulations and guidance documents for
4.2 This guide provides the tests, procedures, and param-
information on other treatment processes or for specific re-
eters that should be considered to significantly reduce patho-
quirements for use or disposal of biosolids.
gens in wastewater treatment plant solids by the addition of
1.2 Additional requirements may be imposed by individual
manufactured or by-product alkaline materials (1).
states,andtheseareavailablethroughstateregulatoryagencies
that issue permits for treatment and use or disposal, or both, of
5. Alkaline Materials Characteristics
biosolids.
5.1 Chemical Composition:
Alkaline materials may be tested for Available Lime Index
2. Referenced Documents
(ALI) in accordance with the optional chemical test ofTable 1.
2.1 ASTM Standards:
Other chemical components, if required, may be determined in
C 25 Test Methods for Chemical Analysis of Limestone,
accordance with the appropriate procedure when requested by
Quicklime, and Hydrated Lime
the purchaser.
C 110 Test Methods for Physical Testing of Quicklime,
5.2 Reactivity:
Hydrated Lime, and Limestone
5.2.1 Alkaline materials should be tested for pH and heat of
2.2 USEPA Publication:
hydration (heat rise or slaking rate) in accordance with the
Title 40, Code of Federal Regulations (CFR), Part 503,
recommended tests of Table 2.
StandardsfortheUseorDisposalofSewageSludge;Final
3 5.3 Physical Characteristics:
Rules, 58 FR 9248-9404
5.3.1 Alkaline materials should be tested to determine the
3. Terminology particle size in accordance with the recommended physical
tests of Table 3.
3.1 Acronyms:acronyms—these are defined by operating
parameters (for example, time, temperature) whose values
6. Process Performance
must be met in order for biosolids to be used in various ways
6.1 PFRP (Class A) Alkaline Treatment of Biosolids:
as a nutrient source/soil conditioner. Ref. 40 CFR Part 257.
6.1.1 Mixing—Thorough mixing of the biosolids and stabi-
3.1.1 PFRP—Processes to Further Reduce Pathogens
lization reagent must be provided to ensure uniform pH
(equivalent to 503 Class A).
distribution and pathogen reduction throughout the biosolids
mass (2). Effective mixing depends upon achieving the appro-
priate ratio of alkaline material to biosolids cake uniformly
This guide is under the jurisdiction of ASTM Committee C07 on Lime and is
the direct responsibility of Subcommittee C07.04 on Environmental Uses.
distributed throughout the treated biosolids.
Current edition approved April 10, 1998. Published September 1998.
6.1.1.1 Biosolids with a high moisture content will require
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
less mixing energy than high-solids biosolids cake.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
3 4
Available from the Superintendent of Documents, U.S. Government Printing The boldface numbers in parentheses refer to the list of references at the end of
Office, Washington, DC 20402. this guide.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6249–98 (2004)
TABLE 1 Optional Chemical Test
TestMethodsC 25)togenerateheatandelevatepH.Generally,
Test Method Component Specification drybiosolidscakes(18to30 %)requireamoreintimatemixto
A
C 25 Available Lime Index (ALI), %
ensure proper penetration and reaction than is required by wet
A
To be specified only as required by purchaser.
biosolids (less than 18 %).
6.1.4.2 The calcium oxide in the reagent must react with the
TABLE 2 Recommended Reactivity Tests
moisture in biosolids (hydration) producing calcium hydroxide
ASTM Test Method Component Specification and heat. The moisture content in the biosolids mass must be
A
C25 pH $ 12.0
sufficient to allow the hydration reaction to occur between the
B C
C110 Heat rise, C
selected reagent (CaO concentration and fineness) and biosol-
A
Based on 40 CFR Part 503 for pH >12 for 2 h or more.
ids mass.
B
Modify Test Method C 110 to proportion alkaline reagent in lieu of quicklime.
6.1.4.3 Biosolids cakes with a high moisture content will
Alkaline material and water ratio may need to be modified to obtain measurable
results. Any modification of Test Method C 110 must be clearly stated on the
tend to react faster than biosolids with a low moisture content.
analysis report.
6.1.5 Biosolids Type:
C
To be specified only as required by purchaser.
6.1.5.1 Case-by-case alkaline material demand should be
determined for each biosolids type through pilot testing using
TABLE 3 Recommended Physical Test
the actual biosolids cake and proposed reagents for each
ASTM Test Method Component Specification
project. Develop process guidelines for alkaline additions by
A
C 110 Amount retained on 600 µm
biosolids type and alkaline additive characteristics.
(No. 30 mesh), %
6.1.5.2 Biosolids with a high moisture content may require
C 110 Amount retained on 75 µm
A
(No. 200 mesh), %
a higher dose ratio than drier dewatered biosolids cake when
A
To be specified only as required by purchaser.
dosage ratios are expressed on a dry weight basis.
6.1.6 Reaction Time and Curing Time:
6.1.6.1 Heatwillbegeneratedashydrationofcalciumoxide
6.1.1.2 Biosolids characteristics will determine the proper
occurs. The reaction time will vary depending on reagent
type of equipment or system required for adequate mixing.
composition moisture content of the biosolids mass, and mixer
Incomplete mixing can cause odor release during product
efficiency.
storage or application and may lead to failure to meet regula-
6.1.6.2 Reaction times to effect pathogen reduction are
tory requirements for pathogen and vector control.
established by applicable federal and state regulations.
6.1.2 Particle Size:
Reaction/cure times depend upon a number of variables and
6.1.2.1 Given an adequate moisture supply using alkaline
should be pilot-tested using the actual biosolids cake, alkaline
agents (for example, CaO) with smaller particle sizes will
admixture, mix unit, cure vessel, and testing protocol and
facilitate rapid and efficient mixing of agents with biosolids
acceptance criteria to assure compliance with regulatory stan-
and increase reaction rates and pH, resulting in higher tem-
dards.
peratures and greater pathogen reduction.
6.1.6.3 For alkaline treatment processes, one of the three
6.1.2.2 Since dusts are more easily generated from finely
performance criteria is required:
divided particles, precautions should be taken to prevent
(1) The time-temperature relation established in 40 CFR
exposure to eyes and mucous membranes, which may result in
503.32 (a) (3) (Alternative 1). Selected time-temperature
irritation.
values are as follows:
6.1.2.3 Reactivity and particle size also affect the rate of
Biosolids Temp, °C 50 55 60 65 70 75 80
dust and mist emissions from reactors or mixing devices, or Moisture >7 % Time, hours 316 63 13 2.5 0.5 0.10 0.020
Moisture <7 % Time, hours 120 24 4.8 0.95 0.19 0.04 0.008
both. Particulate release may require scrubbing, water spray, or
other emission controls on reactors or mixing devices for (2) The pH-time, temperature-time, drying procedure in 40
aesthetic reasons or to meet regulatory requirements.
CFR 503.32 (a) (4) (Alternative 2). Basically, the biosolids are
6.1.2.4 Very small particle size may also lead to “air held at a pH above 12 for 72 hours with a 12-hour period in
slaking”orrecarbonationofactivelimeparticlesifthematerial
which the temperature exceeds 52°C, followed by air drying to
is exposed to high humidity.Air slaked/recarbonated materials a solids content exceeding 50 %.
will not achieve the pH necessary to meet regulatory require- (3) Pasteurization (40 CFR 503, App. B, Part B—PFRP
ments. Option 7) in which the biosolids are maintained at a minimum
6.1.3 Reactivity (Heat and pH Elevation): temperature of 70°C for 30 minutes.
6.1.3.1 Reactivity is dependent upon the interaction be- 6.1.6.4 Ammonia or other odors released may require water
tween the alkaline reagent and the material to be treated. spray, scrubbing, gas capture, or control of emission.
Reactions occur as the alkaline material contacts the biosolids. 6.1.7 Reaction/Cure Vessels or Containers:
The finer the alkaline product, the greater the potential for a 6.1.7.1 Consideration should be given to minimize heat
more rapid pH/temperature elevation. losses through materials management, configuration, and ma-
6.1.3.2 Reagent reactivity affects mixing time and dosage terials of construction for processes that require extended
rate and must be considered in process design. curing times.
6.1.4 Moisture Content: 6.1.7.2 Proper temperatures can be maintained without an
6.1.4.1 Adequate moisture must be present to react with the insulated vessel by adding adequate alkaline reagent to com-
free CaO (as measured by Available Lime Index, ALI, as per pensate for heat loss. However, some situations may benefit
D6249–98 (2004)
from an insulated vessel to efficiently retain the heat to meet 6.2.1 Mixing—Thorough mixing of the biosolids and
PFRP temperature requirements. chemical reagent must be provided to ensure uniform pH
distribution and pathogen reduction (2). Mechanical mixing to
6.1.7.3 For processes using a windrow, at a minimum, the
achieve a homogeneous blend of reagent throughout the
mixture should be at least 18 inches thick at all locations in the
biosolids mass depends upon a number of factors, including
pile to ensure heat retention throughout the entire mass for the
achieving the proper ratio of alkaline reagent to biosolids, and
applicablecuringtime.Thinareasatthepileextremitiesshould
sufficient moisture to enable the reaction to occur.
be avoided as they will not retain adequate heat and can lead to
potential regrowth and recontamination of the entire mass. 6.2.1.1 Incomplete mixing or an inadequate reagent dosage
rate can cause odor generation and release during product
6.1.8 Process Testing Requirements:
storage or application and failure to meet regulatory pathogen
6.1.8.1 Process testing requirements vary with the specific
or vector control requirements.
alkaline process selected.
6.2.2 Alkaline Reagent Particle Size:
6.1.8.2 Temperature and pH measurements for the requisite
6.2.2.1 Reactions occur as the alkaline reagents contact the
time periods should be recorded to comply with pathogen
moist biosolids particles. The rate of reaction of the alkaline
reduction (and vector attraction reduction). Daily testing may
reagent tends to increase with: (1) finer reagent particle size,
include monitoring and documenting the elevated temperature
and (2) increased free moisture content. Reagents with a finer
and pH for a predetermined period of time (see 6.2.6 for
(smaller) particle size distribution generally are more easily
details). Some methods also require documentation of reduced
and uniformly blended into the biosolids.
moisture content and mixing.
6.2.2.2 When using an alkaline slurry, or treating liquid
6.1.8.3 Procedures to monitor or collect samples for analy-
biosolids, particle size may not be as critical as long as
sis are developed for each project based upon site-specific
sufficient mixing and reaction time are provided.
conditions considering the process selected, equipment uti-
lized, volumes of materials to be processed, local state and 6.2.3 Reactivity (pH elevation):
federal regulatory requirements, and local conditions (3).
6.2.3.1 Caremustbetakentoensuremoisturewillnotcome
into contact with the reagent prior to entering the mixer. Air
6.1.9 Process Testing Schedule:
slaking of the alkaline reagent can be a problem in long-term
6.1.9.1 Testing must be conducted in accordance with fed-
storage or pneumatic transfer systems. Guidance for proper
eral, state, and local regulations. Product testing, to meet
storage of reactive alkaline materials can be found in Lime—
end-use requirements, will be site-specific. Under 40 CFR Part
Handling,Application and Storage, National LimeAssociation
503 regulations, pathogen (salmonella, virus, protozoan, and
Bulletin 213.
helminth egg) or indicator organism testing and pollutant
concentration (metals) testing requirements are: 6.2.3.2 Increasing the alkaline reagent oxide concentration
may increase potential for reactivity.
Amount of Biosolids
(dry metric tons/365 days) Frequency
6.2.4 Moisture Content:
6.2.4.1 Moisture content affects the pH by permitting the
> 0 and < 290 Once per year
$ 290 and < 1500 Once per quarter
alkaline reagents to dissociate, releasing hydroxide ions, in-
$ 1500 and < 15 000 Once per 60 days
creasing the pH. As moisture increases, it is easier for the
$ 15 000 Once per month
alkaline material to disperse, penetrate, react, and dissociate,
6.1.9.2 In addition, at a minimum, daily operating records
thus generating hydroxide ions throughout the mixture.
shouldbemaintaineddocumentingcompliancewithapplicable
6.2.4.2 Care should be exercised when working with bio-
requirements (for example, process time/temperature, pH,
solids cakes with greater than 30 % solids content to ensure a
solids concentrations, and fecal coliform levels) (4).
complete uniform reaction is achievable.
6.1.10 Product Solids Content:
6.2.5 Biosolids Type—Biosolids characteristics will impact
6.1.10.1 Product utilization may be affected by solids con-
on the required dosage rates for specific alkaline reagents.
tent to aid in control of microbial regrowth during storage to
There
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