Characterization of odors from limed biosolids treated with nitrate and anthraquinone.

Abstract

Complaints from the public due to odor emissions are one of the biggest problems associated with any biosolids land application program. Chemical additives to reduce or mask odors are one option for producers; however, many chemicals are too expensive or are too unstable to use safely. This project provides a preliminary evaluation of nitrate or nitrate + anthraquinone as additives in controlling odors from limed biosolids. Over a twenty-four day period, odors were measured in the headspace over several treatment levels using two different chemical analysis tools along with olfactometric evaluation of odor intensity and hedonic tone. On six days during the sample period, hydrogen sulfide was measured using a Jerome 631X, a sensor that also responds to other reduce sulfur gases. Other specific sulfides, amines, and mercaptans were also determined using solid phase microextraction with gas chromatography-mass spectrometry. A simple sniff test approach was used with six panelists on five days during the project. The chemical analysis results revealed that the addition of nitrate and especially nitrate + anthraquinone was effective in reducing concentrations of hydrogen sulfide and methylmercaptan when compared to untreated limed biosolids. However, the olfactometric results did not reveal any significant differences between treatments. The panelists also found that all treatments exhibited a fishy or ammonical character, indicative of amines, or ammonia. More advance olfactometric analysis utilizing dilution techniques might have been able to distinguish between treatments, but it is likely that amines were the dominant odorant released from all treatments. This preliminary project suggests that chemical addition of nitrate or nitrate + anthraquinone would be most effective in controlling odors from unlimed biosolids such as anaerobically digested materials.

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Characterization of Odors from Limed Biosolids Treated with Nitrate andCharacterization of Odors from Limed Biosolids Treated with Nitrate and
AnthraquinoneAnthraquinone
Hyunook Kim a; Laura McConnell b; Mark Ramirez c; Mohammad Abu-Orf d; Hong L. Choi e; Christopher Peot c
a Department of Environmental Engineering, The University of Seoul, Seoul, Korea b US Department of
Agriculture Research Service, Environmental Quality Laboratory, Beltsville, Maryland, USA c DC Water and
Sewer Authorities, Washington, DC, USA d US Filter, Research and Development Division, New Jersey, USA
e Department of Agricultural Engineering, Seoul National University, Seoul, Korea
Online Publication Date: 01 January 2005
To cite this ArticleTo cite this Article Kim, Hyunook, McConnell, Laura, Ramirez, Mark, Abu-Orf, Mohammad, Choi, Hong L. and Peot,
Christopher(2005)'Characterization of Odors from Limed Biosolids Treated with Nitrate and Anthraquinone',Journal of Environmental
Science and Health, Part A,40:1,139 — 149
To link to this Article: DOI: To link to this Article: DOI: 10.1081/ESE-200033653
URL: URL: http://dx.doi.org/10.1081/ESE-200033653
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Journal of Environmental Science and Health, A40:139–149, 2005
Copyright C ?Taylor & Francis Inc.
ISSN: 1093-4529 (Print); 1532-4117 (Online)
DOI: 10.1081/ESE-200033653
Characterization of Odors from
Limed Biosolids Treated with
Nitrate and Anthraquinone
Hyunook Kim,1,∗Laura McConnell2Mark Ramirez,3
Mohammad Abu-Orf,4Hong L. Choi,5and Christopher Peot3
1Department of Environmental Engineering, The University of Seoul, Seoul, Korea
2US Department of Agriculture Research Service, Environmental Quality Laboratory,
Beltsville, Maryland, USA
3DC Water and Sewer Authorities, Washington, DC, USA
4US Filter, Research and Development Division, New Jersey, USA
5Department of Agricultural Engineering, Seoul National University, Seoul, Korea
Complaints from the public due to odor emissions are one of the biggest problems as-
sociated with any biosolids land application program. Chemical additives to reduce or
mask odors are one option for producers; however, many chemicals are too expensive
or are too unstable to use safely. This project provides a preliminary evaluation of ni-
trate or nitrate + anthraquinone as additives in controlling odors from limed biosolids.
Over a twenty-four day period, odors were measured in the headspace over several
treatment levels using two different chemical analysis tools along with olfactometric
evaluation of odor intensity and hedonic tone. On six days during the sample period,
hydrogen sulfide was measured using a Jerome 631X, a sensor that also responds to
other reduce sulfur gases. Other specific sulfides, amines, and mercaptans were also de-
termined using solid phase microextraction with gas chromatography-mass spectrom-
etry. A simple sniff test approach was used with six panelists on five days during the
project. The chemical analysis results revealed that the addition of nitrate and espe-
cially nitrate + anthraquinone was effective in reducing concentrations of hydrogen
sulfide and methylmercaptan when compared to untreated limed biosolids. However,
the olfactometric results did not reveal any significant differences between treatments.
The panelists also found that all treatments exhibited a fishy or ammonical character,
indicative of amines, or ammonia. More advance olfactometric analysis utilizing dilu-
tion techniques might have been able to distinguish between treatments, but it is likely
that amines were the dominant odorant released from all treatments. This preliminary
project suggests that chemical addition of nitrate or nitrate + anthraquinone would be
most effective in controlling odors from unlimed biosolids such as anaerobically digested
materials.
∗Correspondence: Hyunook Kim, Department of Environmental Engineering, The Uni-
versity of Seoul, 90 Jeonnong-dong, Dongdaemun-gu, Seoul 130-743, Korea; E-mail:
h kim@uos.ac.kr.
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140
Kim et al.
Key Words: Anthraquinone; Biosolids; Nitrate; Odor panel; Sulfur compounds;
Trimethylamine.
INTRODUCTION
Offensiveodorisasignificantproblemforthelandapplicationprogramatmany
wastewater treatment facilities. Although most unit processes in a wastewater
treatment plant are potential sources of odor, solid-handling systems, such as
thickening, drying, and lime stabilization are normally the most significant.[1]
The final biosolids product, which can be used as a soil amendment, often also
emits offensive odor, causing public resistance to large scale land application
programs and results in increased regulatory action.
Chemical treatments, especially oxidation technologies, have been applied
to control odors from wastewater and sludge since the 1970s.[2]Hydrogen per-
oxide has been applied to oxidize H2S, mercaptanes, thiosulfate, and sulfur
dioxide in wastewater,[2]and waste activate sludge.[3]However, hydrogen per-
oxide can be dangerous to handle and takes time to react,[4]so several other oxi-
dantsalsohavebeentestedandapplied.Forexample,potassiumpermanganate
was added to raw dewatered sludge to reduce hydrogen sulfide production.[4]
Farooq and Akhlague[5]tested ozone to condition and oxidize heavy metals and
organics in raw and thickened waste activate sludge. They reported a consider-
able reduction in odor released from the sludge, although they did not quantify
their results. De Luca et al.[6]used potassium ferrate to stabilize dewatered
sludge and compared its performance with lime stabilization in terms of odor
control. They found that ferrate was very effective in oxidizing reduced sulfur
and nitrogen compounds and mitigating odors from conditioned sludge. Gao
et al.[7]used sodium hypochlorite to remove 95% of hydrogen sulfide from gas
emissions released from gravity thickened sludge.
While results of these studies are encouraging, none of the oxidants are
widely used, mainly due to high costs. Odor control through the use of hydrogen
peroxide, permanganate or hypochlorite, requires large quantities of chemicals
for conditioning or oxidizing reduced compounds in sludge. For example, to
treat 1 mol of sulfide in sludge 2–5 mol of hydrogen peroxide are required.[3]
Although relatively small amount of ozone and potassium ferrate is required
to oxidize odorants in sludge, they are expensive to produce and they require
special handling.
Lime stabilization is used to condition dewatered sludge and is added
to final biosolids in approximately 20% of wastewater treatment plants in
the US due to its economical advantage over other chemical stabilization
technologies.[8]LimeisaddedtorawsludgeuntilthepHis>12.ThehighpHen-
vironment and exothermic reaction inactivates microorganisms in sludge and
produces a soil like final product. In addition to its disinfection abilities, lime
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Characterization of Odors from Limed Biosolids 141
addition is believed to reduce odors in sludge. However, there are still com-
plaints about odors from limed biosolids on site and in the field where it is
land-applied. Odors from limed biosolids, are often characterized as “fishy”
and “decaying,” pose a major obstacle to the land application program. The
fishy and decaying odors are characteristics of amines (especially trimethy-
lamine: TMA) and reduced sulfur compounds (produced under septic condi-
tions), respectively.[9]
Recently, it was demonstrated that H2S in sewer systems and wastewater
under reducing condition could be diminished by adding nitrate.[10–12]They
also reported anthraquinone added with nitrate enhanced H2S control. The
theoretical basis for the addition of nitrate is that the oxidation state of the
systemischangedsuchthatnitrateratherthansulfateisreduced.Theaddition
of anthraquinone inhibits the long term growth of odor causing microbes.
In this preliminary study, effects of nitrate and anthraquinone addition to
limed biosolids were evaluated with respect to odor quality. This study was ini-
tiatedwiththeassumptionthatiftheseoxidantsblocktheformationofreduced
sulfurs, the odor quality of the final product will be improved. The evaluation of
odors from biosolids with and without treatment using the chemicals was car-
ried out using a simple odor evaluation approach along with a gas analytical
method utilizing solid phase microextraction coupled to gas chromatography-
mass spectrometry. The specific goals of the current study were as follows:
(i)Evaluation of intensity and hedonic tones of odors from limed biosolids
with and without nitrate and anthraquinonone treatment over 20 days.
(ii) Characterization and quantification of specific odorants in the headspace
over limed biosolids with and without nitrate and anthraquinonone
treatment.
(iii) Preliminary assessment of the effectiveness of these chemicals in control-
ling odors in limed biosolids and provision of recommendations for further.
MATERIALS AND METHODS
Sample Preparation
Two different chemical additives, i.e., Bioxide c ? and Bioxide c ?-AQ that are
commerciallyavailablewereobtainedfromUSFilter,Inc.(Warrendale,PA).The
first mainly consists of Ca(NO3)2(425 g NO−
was made by adding 12.2 g of anthraquinone to 1 L of Bioxide.
Unlimed dewatered sludge (25% solids, a blend of gravity thickened sludge
and waste activated sludge), collected from a centrifuge in the Blue Plains
Wastewater Treatment Plant located in Washington, DC, was mixed with lime
and Bioxide in a pilot scale industrial mixer at Blue Plains. Lime was added
3/L Bioxide). The second additive
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Kim et al.
Table 1: Sample matrix under study.
Sample ID
Dosage of Bioxideb
Control BLBMBL-AQa
BM-AQa
0 0.10.5 0.1 0.5
aContains anthraquinone of 100 lbs/1000 gallons of Bioxide.
bUnit of dosage: gallon/ton of dewatered sludge (wet basis).
to the sludge sample at 25% by mass. In each batch, biosolids of 1 wet ton was
mixed with lime and the additives in the mixer. Table 1 presents the treatments
that were used to assess the effect of both Bioxide and Bioxide-AQ.
Analysis of Odorants
Triplicate aliquots of each of the five treatments were collected from the
mixer and transferred to 1-L Teflon containers, and transported to the nearby
U.S. Department Agriculture Agricultural Research Service Environmental
Quality Laboratory located in Beltsville, MD. Upon arrival, the samples were
stored sealed in a hood at 25◦C. In order to monitor the dynamic change of
odorants from biosolids, they were measured at six different times for the study
period; 1, 5, 10, 15, 20, and 24 days after the treatment.
The headspace of each Teflon jar was analyzed for specific odorants using
a flow through system to expose solid phase microextraction (SPME) fibers
(Fig. 1). Just prior to extraction, the headspace of each sample jar was flushed
Figure 1: Experimental set-up for instrumental analysis.
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