Respiration studies on the decomposition of organic waste-amended colliery spoil

Agriculture, Ecosystems and Environment, 32 (1990) 25-38

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Elsevier Science Publishers B.V., Amsterdam

Respiration studies on the decomposition of organic waste-amended colliery spoil N.F.Y. Tam and Y.S. Wong Department ofAppliedBiologyand Chemical Technology, Hong Kong Polytechnic,Hung Horn, Kowloon (HongKong) (Accepted for publication 22 February 1990 )

ABSTRACT Tam, N.F.Y. and Wong, Y.S., 1990. Respiration studies on the decomposition of organic wasteamended colliery spoil. Agric. EcosystemsEnviron., 32: 25-38. Microbial decomposition is an important process determining the fate of organic waste in colliery spoil. Laboratory respiration studies (using modified Birch and Friend respirometers) were conducted to investigate the rate of microbially mediated decomposition in three colliery spoils after amendment of two sewage sludges (Dewmus and Yorkshire Bounty) and two animal manures (Chiguano and Poultry Manure), respectively. Addition of organic wastes significantlyenhanced the microbial respiration rates especially in the two acidic Ashington and Whitwood spoils. In most amended spoils, the relationship between cumulative volume of daily hydrogen liberated and incubation time was best described by quadratic regression models. The regression coefficient provided a good index for decomposition rate. Among the four organic wastes, Chiguano treatment had the fastest decomposition rates, followed by Yorkshire Bounty and Poultry Manure. Dewmus-amended spoil exhibited the slowest decomposition rate, suggesting that this organic waste might be more resistant to microbial attack. Besides waste amendments, addition of ammonium sulphate to colliery spoil also caused a rapid increase in decomposition rate. These findings suggested that the microbial activity was mainly limited by the low nitrogen content in the control spoil. In general, the microbial respiratory activities of the three spoil types receiving the same amendment were not significantly different from each other. This finding implied that the decomposition rate of organic amendment in colliery spoil was independent of the types of spoil. At the end of the 44-day incubation period, the amount of carbon mineralized from added organic wastes varied from 10 to 37%, in the order of Yorkshire Bounty>Chiguano=Poultry Manure > Dewmus. In general, the proportion of carbon mineralized from these four organic wastes was relatively small. This reflected the slow-release characteristics of organic waste.

INTRODUCTION

Colliery spoil has caused wide concern in many countries because of its pollution problem, and it is desirable to reclaim spoil heaps as quickly as possible. Natural revegetation occurs only slowly and spoil heaps remain bare for many years (Johnson and Bradshaw, 1979). Many studies have found that application of organic waste enhances the amounts of available nutrients, imO167-8809/90/$03.50

© 1990 - - Elsevier Science Publishers B.V.

26

N.F.Y. TAM AND Y.S. WONG

proves spoil physical conditions and also helps to neutralize extreme spoil reaction (Berry and Marx, 1977; Tam, 1984, 1987). On the other hand, application of organic waste such as sewage sludge to land has been considered an inexpensive and environmentally accepted method for waste disposal (Terry et al., 1979a). The rate and extent of microbial degradation in wasteamended spoil directly affects the nutrient mineralization from organic waste and its success as spoil fertilizer and conditioner (Terry et al., 1979a; Sterritt and Lester, 1980; Castellanos and Pratt, 1981 ). It is clear that fundamental changes occurring during decomposition are the uptake of oxygen and the liberation of CO2 by microorganisms, therefore, the measurement of either oxygen consumption or CO2 evolution during incubation provides an estimate of the gross decomposition of organic material (Huntjens et al., 1981; Pagliai et al., 1981 ). Early methods rely mainly upon periodic determination of the amount of CO: evolved and often ignore the daily uptake of oxygen, thus gradual depletion of oxygen may occur during incubation. In this study, a modified Birch and Friend respirometer, based on electrolytic regeneration of oxygen within the apparatus to replace the oxygen consumed by metabolic processes, was used (Birch and Friend, 1956; Wieringa and Mogot, 1957 ). This respirometer allows the amount of oxygen uptake by microorganisms to be measured in terms of the volume of hydrogen liberated from the electrolytic process at any time during incubation. The setup also measures the amounts of CO2 evolved over certain periods or at the end of the experiment. Such respirometer data provide a more complete picture of organic matter decomposition under aerobic conditions. Dobson and Wilson (1964) concluded that both organic wastes and spoils possess a microbial community, which is capable of organic matter decomposition. The rapidity and nature of microbial decomposition depend primarily upon the chemical composition of the organic waste, especially its carbon and nitrogen contents, the rate of application and various features of the substrate environment (Terry et al., 1979a; Reddy et al., 1980; Tam, 1982). Therefore, it is the aim of the present study to evaluate the effect of four different organic wastes on microbial decomposition and carbon mineralization immediately after their addition to three colliery spoil types. The study, based on Birch and Friend respirometers, examines the pattern and rate of oxygen consumption, CO2 evolution and total carbon mineralization during a 44-day incubation period. MATERIALS AND METHODS

Collection and analysis of colliery spoil and organic wastes Spoil samples from three contrasting spoil heaps in the United Kingdom, namely Whitwood (pH 2.7-3.2 ), Ashington (pH 4.7-5.3 ) and Thorne (pH

DECOMPOSITIONOF ORGANICWASTE-AMENDEDCOLLIERYSPOIL

27

6.9-8.1 ) were collected from the spoil surface to a depth of 10 cm. The spoil samples were then air-dried, ground and passed through a 1-cm stainless steel sieve before use. Chicken and turkey manures (namely Chiguano and Poultry Manure, respectively) were collected from local farms; activated and digested sewage sludges (namely Dewmus and Yorkshire Bounty, respectively) were obtained from the Water Authority in West Yorkshire, U.K. These four wastes were stored at 4 °C immediately after collection. The spoil and waste materials were analysed for: pH (pH meter, using 20 g spoil and 40 ml 0.01 M CaC12 solution ); conductivity (conductivity meter); nitrifying bacteria (most probable number (MPN) method (Cochran, 1950; Alexander, 1982 ) ); total organic carbon (Walkley and Black, 1934); total Kjeldahl and inorganic nitrogen (Bremner, 1965); total and Olsen phosphorus (Olsen et al., 1954); total potassium (flame photometer). Properties of the spoils and organic wastes are summarized in Tables l and 2. Each type of organic waste was mixed with the colliery spoil in an amount to supply 100 mg N kg- 1 spoil, aiming to improve the nitrogen status of the colliery spoil. It has been well documented that deficiency of nitrogen is one of the most serious and universal problems in colliery spoil heaps (Reeder and Berg, 1977; Lanning and Williams, 1981 ). Bradshaw and his co-workers (1975) has concluded that rapid accumulation of available nitrogen is the key to the whole reclamation process of spoil heaps. Based on the nitrogen concentration of the organic waste, 6.33, 2.01, 2.23 and 2.24 g of Dewmus, Yorkshire Bounty, Chiguano and Poultry Manure, respectively, were added TABLE 1 General properties of colliery spoils (values indicate mean _+standard deviation, n-- 5 ) Properties

pH Conductivity ( × 10-6 Siemens c m - ~) Moisture(byweight) ( % a t l 0 5 ° C ) Lime requirement (g C a ( O H )2 10 g - ~spoil) OrganicC(%) TotalKjeldahlN (%) C : N ratio Total inorganic N (ppm) N H 2 - N (ppm) NO~--N (ppm) Olsen-P (ppm) K(ppm) Ammonium oxidizer (MPN g- 1 spoil) Nitrite oxidizer (MPN g- ~spoil) nd = not detected.

Spoils Whitwood

Ashington

Thorne

2.69_+ 0.04 637 _+ 10 30.1 _+ 0.5 0.069 3.26_+ 0.14 0.37+ 0.02 8.8: l 19.8 _+ 1.5 15.8 -+ 1.6 3.2 _+ 0.7 2.9 _+ 1.0 115_+ 7 2 1

5.07_+0.01 125 _+6 19.4 _+0.6 0.006 1.22_+0.23 0.14_+0.02 8.2: l 7.0 _+1.9 2.2 _+0.6 4.8 _+1.9 9.6 -+2.7 102_+2 1049 27

7.82_+ 0.05 438 _+ 4 17.5 _+ 0.5 nd 2.05_+ 0.67 0.16-+ 0.03 12.8:1 5.3 _+ 1.9 1.1 -+ 0.5 3.1 _+ 1.0 2.1 _+ 0.2 56 _+21 549 2

28

N.F.Y. TAM AND Y.S. WONG

TABLE 2 General properties of organic wastes (values indicate mean -+ standard deviation, n = 5 ) Properties

pH Moisture (by weight) ( % a t l 0 5 ° C ) OrganieC (%) Total Kjeldahl N (%) C : N ratio Total inorganic N (%) N H + - N (%)

NO~--N (X 10-3 %) Total P (%) K (ppm) Ammonium oxidizer (MPN g- ' waste ) Nitrite oxidizer (MPN g- ~waste)

Organic wastes Dewmus

Yorkshire Bounty

Chiguano

Poultry Manure

6.87+0.04 16.4 +0.5 19.90+0.96 1.58+0.07 12.6:1 0.10+0.01 0.10+0.01 1.48+0.86 1.25+0.14 6906+393 5 1

5.45+0.01 5.8 +0.2 29.20+3.23 4.98"+0.15 6.5:1 0.16"+0.01 0,15+0.01 1.35"+1.74 2.08-+0.09 6814"+2667 ND 6

6.22+0.02 52.7 +0.5 37.54+ 1.79 4.48"+0.22 8.4:1 1.02+0.04 1.01 -+0.04 0.01 _+0.00 1.25-+0.14 19999"+436 ND 8

6.63+0.02 91.0 +1.7 36.56+0.49 4.46+0.24 7.4:1 1.16+0.39 1.25+0.12 0.02+_0.00 2.80+0.83 26172_+740 ND ND

nd = not detected.

to 1 kg of spoil. Ammonium sulphate, a nitrogen source, was mixed with the spoils in the same ratio as the organic wastes and acted as a reference treatment. Spoils without any addition were used as controls.

Respiration studies Amended spoil (20 g), adjusted to 15% moisture content (by weight), was placed in a modified Birch and Friend respirometer (Birch and Friend, 1956 ) and incubated at room temperature (20 + 2 °C) for 44 days. The volume of hydrogen released from the cathode of the respirometer (a measure of oxygen consumed by microorganisms in spoil mixture) was recorded every day. The amounts of daily hydrogen produced were added to the previous evolution and reported as cumulative volume of hydrogen liberated. A blank with pure, sterile sand was used to detect the small daily readings of hydrogen evolution due to minor fluctuations of temperature, particularly overnight. At the end of the 44-day incubation period, total volume of CO2 trapped in the standard N a O H solution was determined and the amount of carbon mineralized was calculated (Hesse, 1971 ). For each kind of amended spoil as well as the controis, three replicates were prepared.

Statistical analysis The relationships between incubation days and the cumulative volumes of daily hydrogen liberated from each treatment were examined by both linear

29

DECOMPOSITION OF ORGANIC WASTE-AMENDEDCOLLIERY SPOIL

( Y= ot + fiX) and quadratic ( Y= ot + fltX+p2X 2) regression models where: Y= cumulative volume of daily hydrogen evolved (ml); X = incubation time (day); fll = initial rate of hydrogen evolved; f12= change in rate of hydrogen evolved. The decomposition rate of each treatment (indicated by the regression coefficient, the fl value), total volume of oxygen consumed, a m o u n t of carbon oxidized and percentage of added carbon being mineralized were analysed by the parametric two-way analysis of variance and Duncan's multiple range test at 5% probability level (Milton and Tsokos, 1983 ). RESULTS AND DISCUSSION

Rate of microbial respiration It is clear that very little microbial respiration had taken place in the control spoils and addition of either organic wastes or a m m o n i u m sulphate significantly enhanced the microbial action of the amended spoil (Figs. 1-3 ). Among the three control spoils, Whitwood displayed the highest rate of hydrogen libWHITWOOD SPOIL 160

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30

N.F.Y. TAM AND Y.S. WONG ASHINGTON SPOIL

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erated, followed by Thome and Ashington (Table 3 ). Whitwood was the spoil having the lowest pH value but the highest nitrogen (both organic and inorganic nitrogen) and organic carbon contents (Table 1 ). The relatively higher microbial activity recorded in Whitwood spoil may be explained by its higher available nitrogen levels. The microbial activities recorded in this acidic Whitwood spoil further suggested the existence of some acid-tolerant bacteria and fungal strains (Jackson, 1967; Deacon, 1984). It could also be a result of the possibility that microbes were afforded protection by the presence of some less acid microsites in acidic spoil (Wilson and Stewart, 1956). Addition of ammonium sulphate (a nitrogen source) significantly increased the rates of hydrogen evolution especially in Ashington spoil (Table 3 ). Ashington spoil contained the highest population size of nitrifying bacteria and the lowest concentration of Kjeldahl nitrogen (Table 1 ), therefore, improving the nitrogen status of this spoil by ammonium sulphate amendment would cause a dramatic increase in microbial respiration. Table 3 reveals that when ammonium sulphate was mixed with Ashington spoil, the initial respiration rate increased more than 20-fold compared with the con-

DECOMPOSITIONOF ORGANICWASTE-AMENDEDCOLLIERYSPOIL

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trol. These results indicated that spoils could develop a microbial population capable of decomposing organic matter but the microbial activity was inhibited by the low level of nitrogen in the control spoil. Wilson and Hedrick (1957) have concluded that nitrogen content and pH of the spoil affect the rate of organic matter decomposition in spoil, the deficiency of nitrogen is by far more important than acidic pH for the spoils studied here. Besides ammonium sulphate, addition of organic wastes also enhanced the microbial respiration of the spoil mixtures. The trend of hydrogen liberation during the incubation period was similar in all organic waste-amended spoils. A rapid initial production of hydrogen was observed in the first few days, followed by a slower rate during the rest of the experiment (Figs. 1-3 ). Such a relationship was described by a quadratic regression model (Y=ol+fliX+fl2X2). The regression coefficient fll exhibited the rate of hydrogen evolved at the beginning of incubation (thereafter known as initial rate ) whereas f12 indicated changes during the latter period of the experiment. Most of the f12 values were small and negative, indicating a gradual decrease in respiration rate as incubation proceeded (Table 3 ). It has been suggested that the small P2 values may be a result of the exhaustion of available nitrogen in the amended spoils, however, Tam ( 1987 ) showed that the concentrations

32

N.F.Y. TAM AND Y.S. WONG

TABLE3 The regression parameters for the quadratic model showing the microbial decomposition in control and waste-amended spoil Colliery spoil

Wastes

a

fl~

f12

Whitwood

Dewmus ( D ) Yorkshire Bounty (Y) Chiguano ( C h ) Poultry Manure ( P ) A m m o n i u m sulphate ( N ) Control (C)

0.80 0.82 4.37 2.30 - 2.30 1.58

3.19 3.28 3.41 1.45 6.05 1.03

- 0.019 -0.011 -0.013 +0.018 - 0.064 -0.006

Ashington

Dewmus ( D ) Yorkshire Bounty (Y) Chiguano ( C h ) Poultry Manure (P) A m m o n i u m sulphate ( N ) Control (C)

4.98 2.07 ! 1.24 6.20 27.15 4.31

4.16 3.85 4.87 3.61 8.86 0.39

- 0.056 - 0.042 -0.053 -0.035 - 0.142 -0.0004

Thorne

Dewmus ( D ) Yorkshire Bounty (Y) Chiguano ( C h ) Poultry Manure (P) A m m o n i u m sulphate ( N ) Control (C)

3.07 - 0.62 2.80 5.91 1.23 4.88

1.61 2.92 3.83 1.11 2.14 0.51

-0.01 l - 0.027 -0.045 +0.014 +0.009 -0.003

Results of Duncan's multiple range test ~ on fl~ values showing the waste effect

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D

P

C

Arrangement for the result of Duncan's test was in a descending order from left to fight; items underlined with the same line denote no significant difference at 5% probability level between them. Model Y= a + fllX+ fl2X2 where y = cumulative volume of daily hydrogen evolved (ml) x = incubation time (day) fit = initial rate of hydrogen evolved 1/2 = change in rate of hydrogen evolved

of available inorganic nitrogen in the spoil mixtures were 20-56/tg g-1 after 44 days incubation. This indicated that nitrogen might not be a limiting factor for microbial activity in the present study. On the other hand, many previous studies demonstrated that microbial respiration may consist of two phases, in parallel to the decomposition of two different organic matter fractions in the waste material: the readily decomposable water-soluble labile constituent and the more resistant component such as lignin-cellulose complexes (Agbim et al., 1977; Sinha et al., 1977; Reddy et al., 1980). The initial rate fit reflects the speed of breaking down the former fraction. In the present study, this rate varied from 4.04 (average rate of the Chiguano amendments) to 2.06 ml H2 day-~ (average rate of the Poultry Manure amended spoils).

DECOMPOSITION OF ORGANIC WASTE-AMENDEDCOLLIERY SPOIL

33

These results suggested that the Chiguano amended spoil consisted of a larger amount of readily decomposable substances than the Poultry Manure. As mentioned above, the initial rates of all waste-amended spoils were significantly higher than the control spoils (Table 3 ). The enhancement effect of organic waste on spoil microbial activity may be attributed to three reasons. Firstly, waste addition enhanced the nitrogen content of the spoil and produced a similar effect as ammonium sulphate treatment. The available nitrogen in the amended spoil was many fold higher than that found in the controls (Tam, 1987 ). Secondly, mixing the spoil with organic wastes such as sewage sludge would introduce large quantities of decomposable substrate which increase the energy supply for soil microorganisms and thus the microbial activity (Terry et al., 1979a,b). In this study, a quantity of 0.5-1.3 g kg-~ organic carbon was added to the spoil when the organic waste was mixed with the spoil (Table 4). Thirdly, it provided a "priming effect". This means addition of waste would stimulate the proliferation of microorganisms already present in soil and thus enhancing the mineralization of native carbon (Sinha et al., 1977; Terry et al., 1979b). When comparing the initial rate of the waste-amended spoils, statistical analysis shows that there was no significant difference among the four organic wastes (Table 3 ). Furthermore, the three colliery spoils receiving the same amendment had a similar degree of increase in its microbial respiratory activity. This suggests that effects of organic waste amendment on the microbial respiration was independent of the differences in spoil texture or chemical properties. Previous researchers have concluded that the decomposition rate of compost or sludge in soil was largely independent of the soil properties, and their rates may be similar in soils which had widely differing textures and chemical properties (Tester et al., 1977; Sommers et al., 1979; Terry et al., 1979a). Total amount o f microbial respiration ~ oxygen consumption and C02 evolution

Table 4 shows the total volume of oxygen consumed and C O 2 evolved during the 44-day incubation period in all treatments. Spoils amended with either organic wastes or ammonium sulphate supported much more microbial gases exchange than the control in all spoil types. In terms of total amount of oxygen consumption, there was no significant difference among the three spoils of the same waste amendment. Ammonium sulphate-amended spoil had the highest volume of oxygen consumption, followed by Chiguano, and Dewmus had the lowest value among all treatments. With respect to CO2 evolution, in general, the amended spoil evolved five to seven times as much CO2 as did the control spoil. Among the three spoil types, Thorne had more CO2 evolved than the other two spoils. This could be explained by the fact that Thorne was

34

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the spoil having neutral pH, the highest concentration of organic carbon and the widest C:N ratio which provide a relatively more favourable condition for the complete decomposition of organic matter, with the evolution of CO2 as the end product. Many studies have determined that the quantity of CO2 evolved is related to the amount of organic matter present, the C: N ratio, the spoil texture, the amendment, and the level and type of microbial activity (Terry et al., 1979a; Reddy et al., 1980). Many respiration studies have shown that when the aerobic chemo-organotrophic microorganisms are dominant species and use carbohydrates as an energy source, the respiratory quotient (CO2:O 2 ratio) should be near to I. In the present study, the average respiratory quotient was 0.20 (range from 0.08 to 0.26, Table 4). Such low values suggested that some microorganisms present in the spoil are actually utilizing oxygen for processes other than microbial metabolism of organic matter. It has been found that the chemo-lithotrophic bacteria such as Nitrosomonas spp., Nitrobacter spp., Thiobacillus ferro-oxidans and Thiobacillus thio-oxidans, have the ability to obtain energy by oxidation of inorganic compounds including ammonium, nitrite, ferrous ion, sulphur and other inorganic sulphur compounds (Rose, 1976). As the colliery spoil is generally acidic with a high content of pyrite (FeS compound), it is possible that some oxygen consumed was actually utilized by Thiobacillus. Furthermore, the waste amendments used in this study contained a high concentration of ammonium-nitrogen (Table 2) which provides a suitable substrate for ammonium oxidizers (Nitrosomonas) and nitrite oxidizers (Nitrobacter). All these processes would take up oxygen but without any release of CO2, resulting in a low respiratory quotient. More studies on the types and population sizes of all these bacteria in amended spoil will be needed.

Carbon mineralization Despite the small amount of CO2 evolution and the low respiratory quotient, addition of organic waste significantly increased the amount of carbon oxidized in all spoil types (Table 4). Effects of organic waste amendments were similar in three spoil types. Among the organic wastes, Dewmus treatment had the least effect in enhancing the carbon mineralization although the amount of carbon added to the spoil was the highest in Dewmus amendments. The percentage of added carbon being oxidized was about 10% in Dewmus treatments. This finding suggested that a large portion of organic matter present in Dewmus, mainly cellulosic in nature, was more inert and resistant to biological decomposition than animal manure. On the other hand, Yorkshire Bounty, the digested sludge, had more than 35% of its carbon mineralized during 44 days of incubation (Table 4) and could be considered as the most easily degraded organic waste. Such discrepancy between two sew-

36

N.F.Y. TAM AND Y.S. WONG

age sludges was difficult to explain especially when the complexity and organic constituents of different wastes were not yet analysed. More work on this aspect will be essential. The two animal manure treatments had a similar proportion of added carbon being oxidized. On the whole, an average of 24.71% (ranging from 10.66 to 36.89%) carbon added via organic waste was mineralized during the 44-day incubation. These values were comparable with those reported by previous researchers (Sommers et al., 1976; Agbim et al., 1977; Tester et al., 1979). As there is significant correlation between carbon, nitrogen and phosphorus mineralization, the small amount of carbon mineralized would be associated with slow releasing of available nitrogen and phosphorus (Agbim et al., 1977; Tester et al., 1977; Castellanos and Pratt, 1981 ). Tam (1987) has also reported the slow-release characteristics of these organic wastes and their long-term benefit in supporting plant growth in these three colliery spoils. ACKNOWLEDGEMENT

The authors would like to thank Dr. M.J. Chadwick and the members of the Derelict Land Reclamation Research Unit of the Biology Department, University of York for their invaluable comments and assistance in many ways.

REFERENCES Agbim, N.N., Sabey, B.R. and Markstrom, D.C., 1977. Land application of sewage sludge: V. Carbon dioxide production as influenced by sewage sludge and wood waste mixtures. J. Environ. Qual., 6:446-451. Alexander, M., 1982. Most probable number method for microbial populations, In: A.L. Page, R.H. Miller and D.R. Keeney (Editors), Methods of Soil Analysis Part 2: Chemical and Microbiological Properties. Series of Agronomy, No. 9 (2), 2nd edn., Madison, WI, pp. 815820. Berry, C.A. and Marx, D.H., 1977. Growth ofloblolly pine seedlings in strip-mined Kaolin spoil as influenced by sewage sludge. J. Environ. Qual., 6: 379-381. Birch, H.F. and Friend, M.T., 1956. Humus decomposition in East Africa soils. Nature, 178: 500-501. Bradshaw, A.D., Dancer, W.S., Handley, J.F. and Shedlon, J.C., 1975. The biology of land revegetation and the reclamation of the China clay wastes in Cornwall. In: M.J. Chadwick and G.T. Goodman (Editors), The Ecology of Resource Degradation and Renewal. Blackwell, London, pp. 363-384. Bremner, J.M., 1965. Inorganic forms of nitrogen. In: C.A. Black, D.D. Evans, J.L. White, L.E. Ensminger and F.E. Clark (Editors), Methods of Soil Analysis. Am. Soc. Agron., Madison, WI, pp. 1324-1345. Castellanos, J.L. and Pratt, P.F., 1981. Mineralization of manure nitrogen - - correlation with laboratory indexes. Soil Sci. Soc. Am. J., 45: 354-357.

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