OCCUPATIONAL HYGIENE IN WASTE TREATMENT PLANTS USING THE STATE-OF-THE-ART TECHNOLOGY

Project leader: Kari Hänninen, University of Jyväskylä, Department of Biological and Environmental Science, P.O.Box 35, FIN-40351 Jyväskylä, Finland, tel. +358-14-602 313, e-mail: Kahannin@cc.jyu.fi
 
 

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TIIVISTELMÄ SUOMEKSI

Researchers:
Anja Veijanen (VOC measurements), e-mail: Veijanen@cc.jyu.fi
Ulla Imppola, e-mail: Ulimppol@cc.jyu.fi
Sanna Lappi
Outi Tolvanen, e-mail: Odessa69@pp.nic.fi
Pia Viilos (viilos@cc.jyu.fi
University of Jyväskylä, Department of Biological and Environmental Science, P.O Box 35, 40351 Jyväskylä Finland

Financing SYTTY organisation: The Academy of Finland
Funding from SYTTY / Total funding of project (€): 142959/231268
Person-months of work funded by SYTTY / Total person-months of work: 49 / 114

KEY WORDS: occupational hygiene, bioaerosol, volatile organic compound, noise
 

EXTENDED ABSTRACT

1 Introduction

Occupational hygiene in landfill and windrow composting areas (Tolvanen et al. 1998) as well as sewage treatment plants has been investigated in Finland earlier. Bad workplace hygiene (for example high concentrations of microbes, endotoxins and volatile, often odorous compounds) has been shown to increase the risk of falling sick and to reduce job satisfaction. With new technologies offering more effective ways to treat wastes, it is important to determine if there still are problems in occupational hygiene. Concentrations may be much higher inside waste treatment plants than in the open waste treatment areas investigated earlier. If careful attention is paid to working hygiene, the problems noted above can be prevented and the costs associated with employee absence and sick leave can be reduced.

In order to find out the problematic points of the occupational hygiene of seven different types of waste management plants, the concentrations of dust, microbes and endotoxins, the noise levels and volatile organic compounds (VOCs) were investigated in this project funded by the Finnish Academy of Sciences and the waste management companies Hyötykapula Ltd, ASJ Stormossen, Tampere Regional Solid Waste Management Ltd, Waste combustion plant of Turku, Turku water works and Rumen Ltd.

2 Methods

Measurements were made (1) drum composting plant in Hyvinkää, (2) in Heinola waste-water treatment plant, (3) in dry waste treatment plant of Tarastenjärvi (Tampere) and (4) in dry waste treatment plant of Ewapower Ltd. (Pietarsaari), (5) in sludge composting plant of Turku, (6) in incineration plant of Turku and (7) in waste treatment plant of ASJ Stormossen in Mustasaari during the years 1998-2001.

The concentrations of air-borne microbes (mesophilic and thermophilic bacteria, fungi and actinomycetes) were determined with a six-stage impactor and by the Camnea method (Palmgren et al. 1986; Heldal et al. 1996). For determination of viable microbes four different substrates were used: malt extract agar and DRCB Agar for fungi, Plate Count Agar (PCA) for bacteria and actinomycetes and Nutrient Agar (½-strong) for actinomycetes. Mesophilic microbes were incubated in 21-25oC from 3 to 7 days, thermophilic in 45oC from 5 to 14 days. The total colony counts for viable microbes are expressed as colony forming units (cfu) per cubic metre of air. In Camnea-method, for determination of both viable and dead microbes the sample with formaldehyde was filtered onto polycarbonate filter and the filter was colored with acridine orange. Microbes were counted with the aid of a fluorescence microscope with magnification x 1000. At least 400 microbes were counted and the total number of microbes was calculated as microbes per cubic meter of air.

Dust concentration (particles > 0.8 µm) and endotoxins were measured according to Finnish Standard No. 3860 (1988). The dust samples were collected onto Millipore cellulose acetate filters and the endotoxins into Fiberglas filters. The concentration of endotoxins was determined by the kinetic Bio Whittaker-QCL method, which relies on the use of the Limulus amebocyte lysate enzyme. Measurements to determine the number of air-borne particles(> 0.3 µm), temperature and relative humidity were made by using an APC Plus-particle counter. The counter divides the particles in the air into four classes: particles > 0.3, 0.5, 1.0 and 5.0 µm. Measurements were made in the breathing zone. The sampling time was 1 minute and measurements were made in 2 to 4 hour periods. Noise level was determined according to Finnish Standard No. 4578 (1982). Noise measurements were made with a Büel & Kjaer Sound Analysis Software BZ 7291 meter. A frequency band “A” and time emphasis “F” were used. Parameters were: 1) LAeq = middle sound level, the effective value of the measurement period, 2) LAEP, d = daily personal sound exposure (EEC 88/186) and 3) LAFmax = maximum sound pressure during the measurement period.

The effects of the waste treatment plants upon the comfort of the residents living in the immediate surroundings of the plants were investigated in the Spring 1999 by an inquire.

Volatile organic compounds (VOCs), ammonia, hydrogen sulphide, oxygen, methane and carbon dioxide were determined in the working air of the waste treatment plants. Samples were taken in all four seasons in Turku, Tampere, Mustasaari and Hyvinkää beginning in summer 1998 and in Heinola beginning in winter 1998/1999. Ammonia was measured by using detection tubes (Dräger ammonia 2/a, 2-30 ppm or 20/a-D diffusion tube, 20-1500 ppm). An infra-red gas analyser (GA 94) was used to measure methane, oxygen, carbon dioxide and also hydrogen sulphide with a plug-in gas pod. Other volatile organic compounds were measured with a gas chromatograph/mass spectrometer (GC/MS, HP5890 series II/VG AutoSpec) system with simultaneous sniffing. Samples were collected with an air pump (flow rate 100 ml/min) into Tenax GR adsorption tubes in amounts varying between 1 and 7 litres. The sample tube was then placed in the analytical equipment and the volatile organic compounds were thermally desorbed into the GC/MS.

3 Results and discussion

Bioaerosols. The best circumstances concering occupational hygiene were at the drum composting plant of Heinola. The most problematic place was the storage room, but the concentrations were low even there. For example, the average concentration of mesophilic fungi was only 2940cfu/m3. Only the total number of microbes (viable and dead) was high, in average 13 million particles/m3.

At the drum composting plant in Hyvinkää there were problems with occupational hygiene in all of the investigated working spaces (waste collection room, engineering room, post-composting tunnel and the cabin of the wheel loader). The amount of viable microbes was highest in the waste collection room during the feeding of the biowaste and in the post-composting tunnel. The presence of microbes in the post-composting tunnel is, however, a natura1 part of the composting process. The concentration of endotoxins was highest in the cabin of the wheel loader, varying from 0.1 to 2800 ng/m3. The threshold value of 200 EU/m3 (about 12 ng/m3) prescribed in the Netherlands was exceeded in several measurements. The noise level exceeded the Finnish threshold value of 85dBA in the engineering room and in the waste collection room.

Microbes were the most notable problem in the processing hall of the dry waste treatment plant of Tarastenjärvi. Also, the concentrations of dust and endotoxins increased occasionally to the level, which might be harmful to human health. For example, the concentrations of endotoxins exceeded the threshold value of 12 ng/m3 in all measurements. The most problematic waste concerning microbes was the dry waste, and during the management of wood waste the dust concentrations exceeded in several measurements the threshold value of 5 mg/m3. The highest dust concentration of 31.03 mg/m3 was measured near the sieve. High microbe and endotoxin concentrations were measured also at the dry waste pelletizing plant of Ewapower Oy, where the endotoxin concentrations ranged in the processing hall from 4.7 to 1000 ng/m3. The noise level exceeded the threshold value of 85dBA both at plants of Tarastenjärvi and of Ewapower Oy.

The concentrations of microbes and endotoxins may increase to the level harmful to health during the crushing of the waste at the waste treatment plant of ASJ Stormossen. The threshold value of 12 ng/m3 for endotoxins was exceeded also in the bioreactor hall. In the drying facilities the noise level was over 85dBA but no other problems with the occupational hygiene were found.

High concentrations of microbes, endotoxins and dust were measured at the waste incineration plant of Turku, e.g. the amount of mesophilic fungi was in average (measurement with impactor) 118225 cfu/m3, and the highest endotoxin concentration was 4700 ng/m3. The noise level exceeded the threshold value of 85dBA in the oven hall.

The results of the inquire of the effects of the waste treatment plants upon the comfort of the residents living in the immediate surroundings of the plants. It was noted that the plant was familiar to most of the respondents. The further away the respondent lived from the plant, the less he/she knew about the plant and the more positive was his/her attitude toward the plant. The most negative attitudes toward the plant were found in Turku incineration plant, and the most positive ones in Pietarsaari. Bad odours were the problem in Heinola. In Turku the increased traffic near the incineration plant, the location of the plant and its effects on comfort of the residential area were viewed as problems. The attitudes toward the plant of ASJ Stormossen were positive. Only few of the respondents felt that the plant spoils the landscape. In Pietarsaari the minor problems were the littering of environment and the increased traffic

Volatile organic compounds. In the drum composting plant in Hyvinkää air samples were taken in three working areas: the engineering room, post composting tunnel and waste collection room. The overall odour was sour, sharp and cow-house-like in the engineering room, more musty and bitter in the post composting tunnel, and putrid and unpleasant in the waste collection room. The odour was strong in the engineering room and the composting tunnel and weaker in the waste collection room. The most abundant compounds in the plant were carboxylic acids (unpleasant, sharp and rancid odours), esters of carboxylic acids (sweet, not always so good), terpenes (coniferous, turpentine), alcohols (alcoholic, sweet) and ketones (musty, unpleasant). Threshold odour concentrations were frequently exceeded, at least in the engineering room and the post composting tunnel. The concentrations of some volatile odorous compounds from the engineering room are presented in table 1. These compounds are examples of typical odour causing compounds found in the air of a biowaste post composting plant. The amounts of identified compounds varied widely during the measurements of the project (from autumn 1998 to summer 2000). In the engineering room the concentrations of many compounds were at their lowest in spring 1999 and summer 2000.

Table 1. The concentrations (mg/m3) of some odour causing compounds in the engineering room of the drum composting plant in Hyvinkää.

Compound	Autumn 98	Winter 98/99	Spring 99	Summer 99	Autumn 99	Winter 99/00	Spring 00	Summer 00
Butanoic acid	2,86	1,87	0,15	0,78	1,08	0,89	2,52	0,39
2-Butanone	1,59	2,01	0,50	0,50	0,91	0,65	2,09	0,24
2,3-Butanedione	1,95	1,92	0,03	0,15	0,12	0,07	0,61	0,10
3-Hydroxy-2-butanone	1,48	1,12	0,01	0,08	0,03	0,02	0,27	0,04
p-Cresol	0,04	0,38	0,002	0,001	0,01	-	0,04	0,02
Limonene	0,50	2,54	1,15	1,47	1,17	2,11	4,79	0,38
Ethyl butanoate	0,09	0,36	0,02	0,39	1,37	0,56	1,84	0,06

In the Turku waste incineration plant air samples were taken in two working areas: the oven hall and the waste bunker. The overall odour was mild or quite mild, cement-like and gravelly in the oven hall. In winter 1998/1999 there was also an ammonia-like odour in the oven hall (NH3: 17 ppm), probably caused by tobacco waste. In the waste bunker the odour was waste-like, sweet and solvent-like. The nuance of the odour depended on the quality of the waste. There were few volatile compounds in the oven hall and the concentrations were usually very low. The identified compounds were mainly terpenes and aromatic hydrocarbons (e.g. toluene and xylenes). Limonene was usually the main peak in chromatograms. The concentration of limonene was considerably greater in spring 1999 and winter 1999/2000. The waste bunker was characterized by alkylbenzenes, limonene, esters of carboxylic acids and hydrocarbons (aliphatic and cyclic). The amounts of some esters of carboxylic acids and alkylbenzenes exceeded threshold odour concentrations, causing a sweet, solvent-like odour. Some alcohols and ketones were found in low concentrations. Small amounts of acetic acid and butanoic acid were found in spring 1999. The concentrations of alkylbenzenes and esters of carboxylic acids were noticeably higher in summer 1998 than at other sampling times (table 2).

Table 2. The concentrations (mg/m3) of some typical compounds in the waste bunker of the Turku waste incineration plant.

Compound	Summer 98	Autumn 98	Winter 98/99	Spring 99	Summer 99	Autumn 99	Winter 99/00	Spring 00	Summer 00
Butyl acetate	1,72	0,28	0,03	0,03	1,03	0,05	0,05	0,03	0,63
Xylenes	2,84	0,19	0,13	0,41	0,79	0,19	0,11	0,008	0,66
Limonene	0,38	0,33	0,38	0,56	0,34	0,19	0,47	0,66	0,49

Air samples were taken in three working areas of the Heinola waste-water treatment plant: the drum composting hall, the gas treatment hall and the storage hall. In the drum composting hall the overall odour was fairly strong, unpleasant and cow-house-like. In the gas treatment hall the odour was mild in winter, spring and autumn but strong in summer. Descriptions of the odour were the same, however: acidic (mineral acid) and sludge-like. The odour in the storage hall was mild during plant shutdowns but strong, unpleasant, sharp and ammonia-like when the plant was running normally. The most abundant compounds in the drum composting hall and gas treatment hall were terpenes. Other compounds were sulphur compounds (mainly dimethyl sulphide and dimethyl disulphide), alkylbenzenes, aldehydes, ketones and aliphatic hydrocarbons. Unpleasant, rancid odours due to carboxylic acids were encountered in summer and autumn of 1999 and 2000 in the drum composting hall. Carboxylic acids were also found in autumn 1999 and in spring, summer and autumn 2000 in the gas treatment hall. The concentration of dimethyl sulphide was at maximum in winter 1998/1999 and autumn 2000 both in the drum composting hall and the gas treatment hall (table 3). The most significant compounds in the storage hall were sulphur compounds and terpenes. In addition alkylbenzenes, aliphatic hydrocarbons, ketones and occasionally carboxylic acids were encountered. p-Cresol, which causes an unpleasant, horse-stall-like odour, was found occasionally in all sampling places.

Table 3. The concentrations (mg/m3) of two sulphur compounds; dimethyl sulphide (DMS) and dimethyl disulphide (DMDS) in the Heinola waste-water treatment plant.

	Drum composting hall		Gas treatment hall		Storage hall
	DMS	DMDS	DMS	DMDS	DMS	DMDS
Winter 98/99	0,70	0,02	0,40	0,01	0,03	0,02
Spring 99	0,05	0,02	0,04	0,01	0,02	0,08
Summer 99	0,30	0,10	0,20	0,04	0,11	0,20
Autumn 99	-	0,007	-	0,02	0,02	0,33
Winter 99/00	-	-	-	-	-	-
Spring 00	0,003	0,01	0,01	0,07	0,21	0,29
Summer 00	0,02	0,007	0,12	0,07	0,19	0,11
Autumn 00	0,52	0,41	0,49	0,42	0,14	0,24

In the dry waste treatment plant in Tampere air samples were taken in one, two or three working areas: the first metal delimiter and the second conveyor on all sampling days and the sieve or bailer occasionally. The overall odour in the processing hall tended to be mild or fairly mild, waste-like or wood-like depending on whether the waste was domestic, energy or wood waste. In all sampling places, terpenes (mainly pinenes, 3-carene and limonene) and alkylbenzenes (mainly toluene, xylenes and ethyl benzene) were the main compounds. Hydrocarbons (aliphatic and cyclic) and some alcohols, esters of carboxylic acids and ketones were found as well. When wood waste was treated the amounts of terpenes were considerably greater than the amounts of other compounds. Also, aldehydes were found when wood waste was treated. Small amounts of acetic acid and butanoic acid were found in winter 1999/2000 when domestic waste was treated in the plant. The concentrations of some volatile odorous compounds are presented in table 4.

Table 4. The concentrations (mg/m3) of some typical compounds in the dry waste treatment plant in Tampere on the conveyor after the first metal delimiter.

Compound	Summer 98	Autumn 98	Winter 98/99	Spring 99	Summer 99	Autumn 99	Winter 99/00	Spring 00	Summer 00
Butyl acetate	1,62	0,19	0,01	-	-	0,16	0,31	0,004	0,32
Xylenes	1,94	0,41	0,07	0.03	0,04	0,51	0,24	0,02	0,99
Limonane	3,46	1,27	0,42	0.28	0,16	0,76	1,32	0,21	0,62

In the ASJ Stormossen waste treatment plant in Mustasaari air samples were taken in two or three working areas: the crushing hall, the bioreactor building and the drying plant. The overall odour in the crushing hall was mild or fairly mild, waste-like. In the bioreactor building the odour was unpleasant, cow-house-like, and in the drying plant it was unpleasant, piggery or cow-house-like and musty. The most important compounds in the crushing hall were alkylbenzenes, hydrocarbons (aliphatic and cyclic), esters of carboxylic acids, terpenes and alcohols. Limonene was the main peak in the chromatograms. Carboxylic acids (acetic acid and/or butanoic acid) were typically encountered in the crushing hall, and alkylbenzenes, aliphatic hydrocarbons and terpenes in the bioreactor building. Sulphur compounds (dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide) were occasionally present in low concentrations, but in summer 2000 the concentration of dimethyl disulphide was many times that on other sampling days (table 5). Alkylbenzenes and terpenes were the most abundant compounds in the drying plant. Acetic acid was found in summer 1999.

Table 5. The concentrations (mg/m3) of some typical compounds in the bioreactor building of the ASJ Stormossenin waste treatment plant in Mustasaari.

Compound	Summer 98	Autumn 98	Sprng 99	Summer 99	Autumn 99	Winter 99/00	Spring 00	Summer 00	Winter 00/01
DMDS	-	-	0,0006	-	0,002	0,001	-	0,02	-
Toluene	0,04	0,05	0,003	0,006	0,02	0,01	0,007	0,08	0,009
p-Cymene	0,02	0,0004	0,07	0,007	0,02	0,05	0,01	0,02	0,005
Limonene	0,02	0,003	0,06	0,01	0,12	0,20	0,06	0,13	0,05

In the sludge composting plant in Turku air samples were taken in the maintenance room, gas treatment room and sieve room. In all three locations, the odour was offensive and sharp. The odour was strong or very strong in the maintenance and sieve rooms, and weak in the gas treatment room. In summer and autumn 1999, the odour was extremely strong and sharp in the maintenance room, mainly due to the great amount of ammonia. The most important compounds in the maintenance room were sulphur compounds (dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide), terpenes, alkylbenzenes and hydrocarbons (aliphatic and cyclic), and in summer and autumn 1999 great amounts of carboxylic acids were present as well (table 6). Carboxylic acids caused very unpleasant acetic and rancid odours, while sulphur compounds gave unpleasant putrid odours. In the sieve room there were, among others, sulphur compounds, terpenes and aliphatic hydrocarbons. The concentrations of carboxylic acids increased considerably during summer and autumn 1999, but were still lower than in the maintenance room. Concentrations of VOCs were much lower in the gas treatment room than in other sampling places. Dimethyl disulphide was found on all sampling days. Among other compounds were hydrocarbons and terpenes.

Table 6. The concentrations (mg/m3) of some typical compounds in the maintenance room of the sludge composting plant in Turku.

Compound	Summer 98	Spring 99	Summer 99	Autumn 99
2-Butanone	-	0,05	-	0,57
DMDS	0,06	0,23	1,25	1,35
Butanoic acid	-	-	3,85	1,86
p-Cresol	-	-	0,74	0,29

In the drum composting plant of Hyvinkää, the concentration of ammonia ranged from 0 to 7 ppm, except in summer 2000 when it rose to 25 ppm in the storage hall. In the waste incineration plant of Turku city the concentration of ammonia was 0-4 ppm, except in winter 1999 when it was about 17 ppm. In the Heinola waste-water treatment plant the highest concentration of ammonia, 40 ppm, was measured in the storage hall in spring 2000. On other sampling days concentrations were just 0 to 13 ppm. In the drum composting hall and gas treatment hall the concentration of ammonia was at maximum 2 ppm. In the dry waste treatment plant in Tampere ammonia was detected in very small amounts (<<1 ppm) or not at all. In the organic waste treatment plant in Mustasaari concentrations of ammonia were 0-2 ppm except in spring 2000 when 5 ppm was measured in the drying plant. In the sludge composting plant in Turku the concentration of ammonia was 10-50 ppm in the sieve room, 0-1.5 ppm in the gas treatment room and 0-450 ppm in the maintenance room. The highest concentrations were measured in summer 1999. The Finnish threshold value for ammonia is 25 ppm.

The concentration of methane was usually below the detection limit (0,1%) in all plants except in Mustasaari and Heinola where the concentration of methane was 0,1% at some sampling times and in Hyvinkää where the concentration was once 0,2%.

The concentration of hydrogen sulphide was 0-1 ppm in Mustasaari organic waste treatment plant, Heinola waste-water treatment plant, Hyvinkää drum composting plant and Turku composting plant. In Tampere dry waste treatment plant and Turku waste incineration plant hydrogen sulphide was not detected.

4 Conclusions

The two most common fungi in the working air at every plant were Penicillium and Aspergillus (e.g. Aspergillus fumigatus). The aerodynamic diameter of most of the viable microbes at every plant was less than 5 µm. The particles of this size can penetrate deep into the alveolus and cause health hazards. The results of an inquiry showed that 61.3% of the employees who answered the inquiry suffered a dry cough. The employees had also other symptoms like itch, rhinitis, and irritated eyes. 6.3% of the respondents were suffering the symptoms daily, while most of the respondents (66.4%) had symptoms few times in a month. Because these symptoms can be work-related it is recommended to use a respirator mask (class P3) in those working spaces where the concentrations of bioaerosols have been verified to be high.

The Finnish threshold values of work environment were not exceeded by a single volatile organic compound but the synergy of these compounds is not known.
 

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