Abatement of Odor Emissions from Landfills Using Natural Effective Microorganism Enzyme

Concentrations of ammonia (NH3), hydrogen sulfide (H2S) and methyl mercaptan (CH3SH) are high in the air above landfills in Taiwan. Odors are strong and many flies are present. These factors were studied in the air above selected landfill sites where odor was considered to be a nuisance. In this study, Natural Effective Microorganisms Enzyme (NEME) was sprayed on selected sampling sites to reduce the odor, the concentration of NH3, H2S and CH3SH and the number of flies in landfills. The odor levels, the concentrations of NH3, H2S and CH3SH and the numbers of flies at various sampling sites before and after spraying with NEME were discussed. Results revealed that at the Tian-Wai-Tian Landfill in Ji-Long City, after NEME was sprayed, the measured odor level ranged from 190 to 552, and the reduction ratios were 99.4%. At the Yan-Pu Country Landfill, after it was spraying with NEME, the measured odor level had a mean of 1360 and the reduction ratio had a mean of 71.6%. At the Ping-Tung Municipal Landfill, after it was sprayed with NEME, the measured odor level had a mean of 602 and the reduction ratio averaged 68.1%. The reduction ratio of NH3 from landfills averaged 72.2% and 61.1% at the Yan-Pu Country Landfill and the Ping-Tung Municipal Landfill, respectively. However, both before and after spraying with NEME, the measured H2S and CH3SH concentrations at both the Yan-Pu Country Landfill and the Ping-Tung Municipal Landfill were under 0.03 ppm. The reduction ratio of the number of captured flies averaged 55.0% and 39.7% at the Yan-Pu Country Landfill and the Ping-Tung Municipal Landfill, respectively.


Introduction
People in Taiwan have recently encountered many air pollution problems, especially those associated with bad odor (Chung et al., 2000).Over 300 *Corresponding author: Tel: +886-8-7740263 Fax: +886-8-7740256 E-mail address: chensj@mail.npust.edu.twsubstances have been reported to have bad odors (Ikeda et al., 1980).Among these, ammonia (NH 3 ), hydrogen sulfide (H 2 S) and methyl mercaptan (CH 3 SH) are three of the nastiest.Large quantities of NH 3 , H 2 S and CH 3 SH are generated and released from landfills, agricultural activities, traffic and industrial processes, including petrochemical refining, metallurgy, food preparation, wastewater treatment and the treatment of fuels (Eikum and Storhang, 1986;Ryer-Power, 1991;Chung et al 2000).Tables 1 and 2 present typical emission gases from landfills and typical emission gases related to trace species from landfills, respectively.
Furthermore, the generation of odors is a complex process that involves several bacterial species, which produce an extensive range of volatile organic compounds in the various currently used manure storage systems.(Jun, 2000).Buijsman et al. (1987) showed that agricultural emissions are primarily from animal waste (chiefly from cattle, poultry, pigs and sheep) and to the use of fertilizers (mostly ammonium sulphate, ammonium nitrate, ammonia, urea and ammonium phosphate) (Buijsman et al., 1987).Battye et al. (1994) stated that the most significant source of NH 3 emissions (around 80%) in the United States is livestock waste (Battye et al., 1994).Perrino et al. (2002) measured the atmospheric concentrations of gaseous ammonia at several traffic sites in the urban area of Rome and at an  (Perrino et. al., 2002).They found that ammonia at the roadside is present in high concentrations, around five times the urban background.
Furthermore, the trend in the concentration of ammonia with time is similar to that of carbon monoxide and depends on traffic emission and on the mixing of the atmosphere.In particular, the air temperature also governs the atmospheric concentration of ammonia (Perrino et. al., 2002).(Thomas et al., 2002).
Ammonia is importantly involved in aerosol processes and influences the acidity of precipitation.
Until now, little information has been available on ambient NH 3 levels in large areas of the world.Carmichael et al. (2003)  Europe and found that median ammonia concentrations ranged from 20 ppb in Dhangadi, India, to < 1 ppb at nine stations.At 27 regional stations, the ambient ammonia levels exceeded 1 ppb (Carmichael et al., 2003).The high median NH 3 concentrations in the Indian sub-continent, Southeast and South Asia and Africa, reflect high NH 3 emissions due to agricultural activities (including fertilizer use), livestock, and the use of biofuels (such as animal dung) as domestic fuel (Carmichael et al., 2003).Carmichael et al. (2003) demonstrated that their observations reflected the spatial distributions of the emissions.Ammonia is a primary pollutant, and is emitted in large quantities near important urban and industrial centers.
However, ammonia emission is in fact wide spread, reflecting the large contribution by agricultural activity (Carmichael et al., 2003).
H 2 S is a colorless gas that smells of rotten eggs.
H Studies undertaken in the last decade have shown that the concentration of hydrogen sulfide varies between 5 and 200 mgm -3 in the air in the odorous part of the city of Izmir (Aysen Muezzinoglu, 2003), depending on the season.Clanton et al. (1999) stated that maximum concentrations of 0.05 mgm -3 methane thiol, 0.112 mgm -3 dimethylsulfide and 3.92 mgm -3 H 2 S in air samples from a manure storage area.Clanton et al. (1999) found 20 of the sulfur-containing compounds for which they searched; however, only H 2 S, carbonyl sulfide, methane thiol, dimethylsulfide, carbon disulfide and dimethyldisulfide was detected in the air samples.
Currently, the Taiwan EPA sets the ambient air standards of 1 and 0.1 ppm for NH 3 and H 2 S, respectively.In a study of exhaust gas treatment, Chung et al. (1996a,b) proved the value of immobilized-cell technology, which was associated with its high removal efficiency, high removal potential, and high operational stability (Chung et al., 1996a,b).Chung et al. (2000) showed that a specific microflora (mixture of Thiobacillus thioparus CH11 for H 2 S and Nitrosomonas europaea for NH 3 ) was immobilized by Ca-alginate and packed inside a glass column to decompose H 2 S and NH 3 .The biofilter packed with co-immobilized cells was continuously supplied with H 2 S and NH 3 gas mixtures in various ratios, and the removal efficiency, the removal kinetics and the pressure drop in the biofilter were monitored.Their results indicated that the efficiency remained above 95%, independently of the ratios of H 2 S and NH 3 (Chung et al., 2000).
A continuous air flow enclosure method was used to measure NH 3 volatilization in a field experiment at an agricultural college in Jiangsu Province.The five treatments used application rates of 0, 100, 200 or 300 kg N ha -1 for urea, in each growing season with rice straw amendment when wheat was sown, and 200 kg N ha -1 without rice straw amendment.Three replicates were in a randomized block design.Ammonia volatilization was measured immediately after urea was applied in the three consecutive years from 1995 to 1997.
The results indicated that N losses due to NH 3 volatilization accounted for 4-19% of the N applied during the wheat growing season and 5-11% during the rice growing season.Ammonia volatilization was significantly affected by the moisture and temperature of the soil before and after fertilizer was applied during the wheat growing season (Tian et al., 2001).
Various economic activities cause both industrial and municipal wastes to be released.The final depository of most of these wastes is a landfill site in which degradation takes place in an acidic anaerobic environment, causing odor to be emitted to the surroundings (Davoli et al., 2003;Vandergheynst et al., 1988).The observations in this work should be carefully considered in view of the difficulty in using the landfill sites in Taiwan.
The comprehension of the fate of NH NEME has a pH value of between 4.5 and 6.5, a density between 0.9 and 1.1, and a total bacteria number >400,000,000 CFU/ml.

Sampling and Analysis Method Effective
Three typical landfills in Taiwan were selected to The collected air-samples were analyzed by gas chromatography (GC) or gas chromatograph mass spectrum analysis (GC-MS).Both a flame ionization detector (FID) and a flame photometric detector (FPD) were used to perform GC analysis.No panel member tested for more than 4 hours per testing.Within the period of testing, at least two ten-minute breaks were taken for olfactory rest.In particular, the odor panels worked in a room constructed of odor-free materials and equipped with a ventilation system to prevent the build-up of odor in the room.

Preparation for the Laboratory Test
Before the spraying process, the feasible for  NEME concentration).Each condition was repeated three times, with the times of 8hr and 16hr.
Table 5 presents the prior to test with different retention times after NEME was added in the laboratory.
Based on the results of Table 5, the feasible dose of NEME in the field was obtained as follows.
Use a total reactor volume of 200 l (in the mixing tank).
(i) Add 100 l about half of the volume of water to the mixing tank.(ii) Add 1.6 l of sugar-mixtures and 1.6 l of NEME into the mixing tank.
(iii) Add water to reach an exact volume of 200 l in the mixing tank.
(iv) Wait for at least one hour before the spraying process.
(v) Sprays about 15 m 3 /day on each sampling site.

Odor Level Emitted from Landfills
Table 6 indicates that the measured odor level at the Tian-Wai-Tian Landfill in Ji-Long City ranged from 912 to 32784 before NEME was sprayed.The results imply that an increase in the mean temperature of the ambient increases the mean level of the odor.However, the results also show that a decrease in the ambient mean relative humidity tends to increase in the mean level of the odor at the Tian-Wai-Tian Landfill.The atmospheric pressure and mean wind speed seem to be unrelated to the mean level of odor at the Tian-Wai-Tian Landfill.After NEME was sprayed, the measured odor level at the Tian-Wai-Tian Landfill in Ji-Long City ranged from 190 to 552.
The reduction ratios were between 39.5% and 99.4%.
Table 7 shows that the measured odor level ranged from 2020 to 7090 with a mean of 4790 at the Yan-Pu Country Landfill, before NEME was sprayed.After NEME was sprayed, the measured odor level ranged from 127 to 3490 with a mean of 1360.The mean reduction ratio was 71.6%.
Table 8 shows that the measured odor level ranged from 1760 to 2050 with a mean of 1890 at the Ping-Tung Municipal Landfill, before NEME was sprayed.After NEME was sprayed, the measured odor level ranged from 123 to 998 with a mean of 602.The mean reduction ratio was 68.1%.

Levels of NH 3 , H 2 S and CH 3 SH Emitted from Landfills
Table 9 shows that the measured NH 3

Summary and Future Works
be investigated: (I) the emission levels of odor, NH 3 , H 2 S and CH 3 SH, and (II) the numbers of flies were examined.These three landfills were the Tian-Wai-Tian Landfill in Ji-Long City, the Yan-Pu Country Landfill in Ping-Tung Hsien, and the Ping-Tung Municipal Landfill in Ping-Tung City.Firstly, at the sampling sites at the Tian-Wai-Tian Landfill, only odor level was examined between December 1998 and May 2000.At the sampling sites at both Yan-Pu Country Landfill and Ping-Tung Municipal Landfill, odor, the number of flies, and NH 3 , H 2 S and CH 3 SH levels were investigated from March to May in 1998.At each sampling site, samples were collected and investigated before and after NEME was sprayed on the landfills.An average air suction rate of 1.5l min -1 was used to obtain ammonia (NH 3 ), hydrogen sulfide (H 2 S) and methyl mercaptan (CH 3 SH) emission samples.This average flow rate was chosen based on ambient air sampling procedures applied to sampling several volatile organic compounds (VOCs) and to determining the concentration of H 2 S in the air, according to NIOSH-6013.This flow rate enabled 20 l of air (total sampling volume) to pass through the sampler during the sampling period.If a higher flow rate had been used, breakthrough of the adsorbent could endanger the sampling procedure.A lower flow rate would cause the experiment to take longer and, considering the warmth of the day, this slowness could have increased the risk of losses due to evaporation (Aysen Muezzinoglu, 2003).During the sampling hours, the temperature of the air varied between 25 and 35 0 C. Vials that contain the extracts of gas chromatographic samples were covered with plastic films before they were capped.Samples and standards were maintained and all handling was performed under a hood, with strong negative pressure to prevent cross contamination (Aysen Muezzinoglu, 2003).
1996).Large plastic bags of with volumes of 20 l were used to collect air samples.Bags and connecting tubing in contact with odor-laden gas should be made of inert material, such as poly-tetra fluro-ethylene (PTFE) or Tedlar, to avoid adsorption onto, or chemical reaction with, the surface of the bag.During the sampling, weather conditions, including wind direction, wind speed and temperature, were recorded.The collected samples were transported to an odor laboratory at the campus of National Ping Tung University of Science and Technology as soon as possible and analyzed within 24 hours.Qualified odor panelists were selected and those who participated in the odor testing were using the five standard odors, as shown in Table4.Sensory evaluations of the odor of all collected air-samples (in air-sample bag) were performed by panels of six to nine people.Panel members with normal senses of smell, were selected in advance using the olfactometer and five standard odors.Table4lists the five standard odors (A to E).Each panel member made a sensory evaluation of the odor of the samples, following the Taiwan EPA procedure and method(EPA-85-3305-09-02, 1996).Panel members were not permitted to eat or smoke for one hour before the session to ensure the quality of their results.Panel members were in the odor room 15 minutes before the measurements were made.They did not use perfumes, after-shave

Table 3
Ammonia occurs naturally, in soil, air and water.Most of the ammonia in water changes to ammonium, an odorless liquid.Ammonia and ammonium can be converted into each other in water.Ammonia is recycled naturally in the

Table 2 .
Typical emission gaseous trace species from landfills.
environment as part of the nitrogen cycle.It does not last very long in the environment.Plants and bacteria rapidly take up ammonia from soil and water.Some ammonia in water and soil is altered to nitrate and nitrite by bacteria.Ammonia released to the air is rapidly removed by rain or snow or by reactions with other chemicals.Ammonia does not build up in the food chain, but is a source of nutrients for plants and bacteria.

Table 3 .
Ambient Air Standards for odour pollution

Table 4 .
Five standard odors used in sensory

Table 5 .
Preparatory test with different retention times after NEME was added in the laboratory.

Table 6 .
Odor level at Tian-Wai-Tian Landfill in Ji-Long City (before and after NEME was sprayed).

Table 7 .
Odor level at Yan-Pu Country Landfill in Pingtung City (before and after NEME was sprayed).

Table 8 .
Odor level at Ping-Tung Municipal Landfill in Pingtung City (before and after NEME was sprayed).

Table 9 .
Mean NH 3 concentration level emitted from various sampling Landfills in Taiwan (before and after NEME was sprayed).

Table 10 .
Mean H 2 S and CH 3 SH concentration level emitted from various sampling Landfills in Taiwan.(beforeand after NEME was sprayed).

Table 11 .
Numbers of captured flies on sticky plates at various sampling landfills (before and after NEME was sprayed).The measured odor level at the Tian-Wai-Tian Landfill in Ji-Long City, ranged from 190 to 552 after NEME was sprayed, yielding reduction ratios of between 39.5% and 99.4%.At the Yan-Pu Country Landfill, after NEME was sprayed, the measured odor level ranged from 127 to 3490 with a mean of 1360, and the mean reduction ratio was 71.6%.At the Ping-Tung Municipal Landfill, the measured odor level ranged from 123 to 998 with a mean of 602 after NEME was sprayed, and the mean reduction ratio was 68.1%.The mean reduction ratios of NH 3 from landfills were 72.2% and 61.1% at the Yan-Pu Country Landfill and the Ping-Tung Municipal Landfill, respectively.Furthermore, before and after NEME was sprayed, the measured H 2 S and CH 3 SH concentrations at both the Yan-Pu Country Landfill and the Ping-Tung Municipal Landfill were under 0.03 ppm.The mean reduction ratios of the number of captured flies landfills were 55.0% and 39.7% at the Yan-Pu Country Landfill and the Ping-Tung Municipal Landfill, respectively.The different values and different trends of emitted NH 3 , H 2 S, and CH 3 SH with time, at the selected sampling landfill sites may not suffice to enable the importance of landfills emissions in determining the amounts of emitted NH 3 , H 2 S and CH 3 SH levels to be deduced.More information can be inferred by comparing the results of future investigations at levels with the background place.