Nitrification in soil treated with domestic and industrial sewage sludge

NITRIFICATION IN SOIL TREATED WITH DOMESTIC A N D INDUSTRIAL SEWAGE SLUDGE

a. O. WILSON

Department of Agronomy, University of Georgia, Georgia Station, Experiment, Georgia 30212, USA

ABSTRACT

Dried sewage sludge from either predominantly domestic or industrial sources was incorporated into soil at rates of O, 1, 4 or 16 mg/g and the soils were incubated with or without the addition of 100 pg/g NH4 + - N at 30°C. Samples were taken at weekly intervals for six weeks and analysedfor N H 4 + - N and (NO 3 ~ + NO 2-) - N. At the two highest rates, industrial sludge reduced nitrification during the first three to four weeks of the experiment, with the highest rate completely inhibiting nitrification for the first two weeks. At the highest rate, the domestic sludge reduced nitrification only slightly. Analyses showed that the industrial sludge contained higher levels of several metals, particularly Zn, Cd and Pb. It was concluded that reduced nitrification at the high rates of industrial sludge was caused by these metals. This conclusion was supported by the finding that nitrification was inhibited in soils treated with 16 mg/g of domestic sludge whichhad been treated with inorganic salts to give concentrations of metals comparable with those in the industrial sludge.

INTRODUCTION

Faced with rapidly rising land prices and restrictive regulations with respect to environmental pollutants, many municipalities are seeking alternatives to the current practice of disposing of sewage sludge in landfills. One alternative is the disposal of sewage sludge on crop land. The agricultural producer is also faced with increasing production costs, particularly for fertiliser. Since, in many cases, sewage sludge increases crop yields, land application of sewage sludge may be beneficial to both the sewage treatment plant operator and the agricultural producer. 73 Environ. Pollut. (12) (1977)--© Applied Science Publishers Ltd, England, 1977

Printed in Great Britain

74

D . o . WILSON

While there are many examples o f positive crop responses to land-disposed sewage sludge (King & Morris, 1972; Milne & Graveland, 1972; Boswell, 1975) some effects this practice might have on soils have to be considered. O n e soil process which could be affected is nitrification. It is i m p o r t a n t that the response o f this process to soil additions o f large quantities o f extraneous materials be thoroughly investigated. There have been several reports relating rates o f sewage sludge application to the rate and extent o f nitrification o f the N added in the sludge (Clark & Gaddy, 1955; Premi & Cornfield, 1969a, 1971; King, 1973; Ryan et al., 1973). M o s t o f these studies have been concerned with efficiency o f N release f r o m sludge materials. Th e experiments reported in the present study were conducted to determine the effect o f two sewage sludges, differing in metal contents, on nitrification o f N H 4 ÷ - N added to soil. TABLE 1 ELEMENTAL COMPOSITION OF SLUDGES AND SLUDGE-TREATED SOIL

Sludge source

Element

Cabin Creek Total N (Domestic) NH4 + - N (NO3- + NO2-) - N Organic C P K Ca Mg Fe Mn Zn Cu Cr Cd Pb South River Total N (Industrial) NH4 + -- N (NO3- + NO2-) -- N Organic C P K Ca Mg Fe Mn Zn Cu Cr Cd Pb

Concentration in sludge

24,000 190 1,150 231,800 13,000 700 15,800 1,100 21,000 370 1,920 350 360 20 450 22,000 130 --* 376,000 15,000 3,700 13,600 3,600 27,400 1,000 9,240 470 980 140 2,900

* (NO3- + NO2-) -- N in this sludge less than 5/ag/g.

Calculated increase in soil concentration by addition of indicated rates of sludge (mg/g) 1 4 16 (/.tg/g) 24 96 0.19 0.76 1-15 4.60 232 896 13 52 0.7 2'8 15'8 63'2 1.1 4'4 2.1 8.4 0.37 1.48 1.92 7.68 0-35 1.40 0.36 1.44 0-02 0.08 0.45 1.8 22 88 0"13 0"52 --376 1,504 15 60 3.7 14.8 13.6 54.4 3-6 14-4 27.4 110 1.00 4.00 9-24 37 -0 0.47 1.88 0-98 3.92 0-14 0.56 2.9 12

384 3.0 18 3,584 208 11"2 253 17.6 33.6 5.92 30.7 5"60 5.76 0.32 7-2 352 2"1 -6,016 240 59.2 218 57.6 438 16.0 148 7.52 15-7 2.24 47

NITRIFICATIONIN SOIL TREATED WITH SEWAGESLUDGE

75

MATERIALSAND METHODS The composition of the two sludges used is shown in Table 1. The values are based on the weight obtained by drying the sludges for three days at 60°C. The 'domestic sludge' was obtained from the Cabin Creek plant near Griffin, Georgia, and is a bed-dried material. The influent to this plant is sewage from a predominantly residential area. The 'industrial sludge" came from the South River plant in Atlanta, Georgia. This material is suction-dried and contains roughly 3 parts of water to I part oven-dry solids as it leaves the suction drum. The influent to this plant is approximately 40 0o domestic sewage with sewage and wastewater from industrial plants making up the remainder. The soil used was a Cecil sandy loam (a member of the clayey, kaolinitic, thermic family of Typic Hapludults) having a pH of 6.6. The elemental composition of the soil is shown in Table 2. The soil contained adequate amounts of P, K, Ca, Mg and TABLE 2 ELEMENTALCOMPOSITIONOF CECILSANDYLOAM Element

Total Nitrogen Organic C P K Ca Mg Fe Mn Zn Cu Cr Cd Pb

Concentration

(/tg/g)

590 8,410 340 4,670 870 850 12,730 490 24 5.4 11 <0-08 5

other nutrients for plant growth and was considered nutritionally adequate for bacterial growth. In treatments receiving NH4 + - N, NH4CI was used to give 100/~g N per gramme of soil. Portions of each of the sludges were dried at 60°C, ground in a mortar and pestle and passed through a 2-ram screen. Due to the inherent heterogeneity of sludges, a representative mixture was obtained by treating bulk samples of air-dry soil ( < 2 mm) with 0, l, 4 or 16 mg/g of the dried sewage sludge. These rates resulted in the increased soil levels of the various constituents indicated in Table 1. The treated soils were adjusted to a moisture content of 12 ~o (approximately 80~o of field capacity) and 10-0 g (oven-dry basis) were weighed into 250-ml glass jars. The jars were closed with plastic caps having a small (1-5 mm) hole in the centre and placed in an incubator at 30°C. Water was added to the bottles every three days to adjust the soil moisture to its original value. At weekly intervals during the six weeks of the experiment, triplicate samples of each treatment

76

D.O. WILSON

were taken and extracted with 100 ml 2M KC1. The steam distillation method (Bremner, 1965b) employing MgO with and without Devarda's alloy was used to determine ( N O 3 - + N O 2 - ) - N and NH4 + - N, respectively, in the extracts. Total N in the soil and sludges was determined using a standard micro-Kjeldahl procedure modified to include nitrates by utilising salicylic acid and sodium thiosulphate (Bremner, 1965a). The amounts o f N H 4 + - N and (NO3- + N O 2 - ) - N in the sludge samples were determined by steam distillation of the KCI extracts in the same manner as described above. Organic C was determined using the Walkley-Black method (Allison, 1965). Analysis of the soil and sludges for the

i 150

Cabin Creek Sludge

o

c ..of

/r----

- "[ " / / , o o

+

Fig.

0

1

" /'/

........ "

I

I

2 3 4 TIM E (Weeks)

J

5

I

6

Nitrificationin soil receiving 100 lzgtg NH4 N and the indicated rates of Cabin Creek sewage sludge.

remaining elements was accomplished as follows. Samples of the dried and ground ( < 2 mm) material were dry-ashed at 550cC for 4 h. The cooled ash was transferred to Teflon containers and the silica removed by successive digestions with concentrated HF at 100c'C. The remaining digest was heated at 100*'C with 6~ HCI until complete solution was obtained. The digest was diluted, P determined by a spectrophotometric method (Murphy & Riley, 1962), K by flame emission spectrophotometry and the remaining elements by atomic absorption spectrophotometry. All pH measurements were made on a 1:2 soil :water suspension. All treatments were replicated three times and mean values are presented.

77

NITRIFICATION IN SOIL TREATED WITH SEWAGE SLUDGE

RESULTS AND DISCUSSION

The accumulation of (NO 3- -F N O 2 - ) - N during the course of the experiment in the soil treated with Cabin Creek sludge and 100 /~g/g NH4 + - N is shown in Fig. I. Similar data for the South River sludge are shown in Fig. 2. The ( N O s - + N O 2 - ) - N values shown in these figures have been corrected for the amount of ( N O n - + NO 2-) - N present in the treated soil at the beginning of the experiment. The data have not been corrected for nitrification occurring in the untreated soil. It is clearly evident that the two sludges affect nitrification in this soil differently. The Cabin Creek sludge (Fig. l) did not have a great effect on the

South River Sludge

150

A

_

Control

,,," - - -

1 mg/g

Z A e

0 Z + I

I

100

........... 4 mg/g --16 mg/g

/, 50

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_.........~

•

./

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..,-

/..%. ..........

v

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J"

/ ///

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0 Z

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0 •

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1

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2 3 4 TIME (Weeks)

Fig. 2. Nitrification in soil receiving 100 ~,g/g NH4 -

•

•

5

6

N and the indicated rates of South River

sewage sludge.

( N O s - + N O 2 - ) - N values except possibly at the 16 mg/g rate. Ort the other hand, the 4 and 16 mg/g rates of the South River 'sludge (Fig. 2) substantially reduced the (NO 3- + N O 2 - ) - N values compared with the control values during the first few weeks of the experiment. Table 3 gives both NH4 + - N and ( N O s - + N O 2 - ) - N values throughout the course of the experiment for the sludge-treated soil receiving either 0 or 100/~g/g NH4 + - N. The values in the table have been corrected by subtracting the NH4 + - N and (NO 3- + N O 2 - ) - N values of the untreated incubated soil.

78

D.O.

WILSON

TABLE 3 EFFECT O F TIME A N D A D D I T I O N S OF N H 4 + - - N A N D S E W A G E S L U D G E O N SOIL N V A L U E S

Sludge source Time o f incubation (weeks)

N H 4 + -- N added (pg/g)

Cabin Creek

South River (rag~g)

1

4

16

I

4

16

NH4 + - N concentration (pg/g)* 0 1

2 3 4 5 6

0 1

2 3 4 5 6

0

1

2

8

0

1

1

100

99

101

107

99

97

98

0

0

0

29

2

7

25

100 0 100 0 100 0 100 0 100 0 100

80 0 42 0 0 0 0 0 0 0 0

99 0 33 0 0 0 0 0 0 0 0

123 0 110 0 20 0 36 0 0 0 0

75 0 16 0 0 0 0 0 0 0 0

94 0 88 0 31 0 0 0 0 0 0

120 19 118 0 124 0 94 0 13 0 22

0 100

4 2

0

9

100 0 100 0 lO0 0 100 0 I00 0 100

26 8 50 5 99 8 104 5 97 I 91

( N O 3 - + N O z - ) - N concentmtion (pg/g)* 6 22 2 0 7 25 3 2 16 27 7 2 19 29 20 2 7 52 5 8 84 51 79 11 25 81 13 4 117 133 98 71 17 64 5 4 116 122 102 105 38 59 2 3 113 150 96 93 16 63 13 --1 120 157 88 95

4 3 -9

-9 -3 -18 2 -- 11 13 25 16 71 3 81

* Values corrected by subtracting values of untreated control. It is a p p a r e n t f r o m t h e N H 4 + - N v a l u e s in t r e a t m e n t s r e c e i v i n g n o a d d e d N t h a t a m m o n i f i c a t i o n is a f f e c t e d relatively little by e i t h e r sludge. A t t h e h i g h r a t e o f b o t h sludges, a p p r e c i a b l e a m o u n t s o f N H 4 + - N a c c u m u l a t e d b y t h e e n d o f t h e first week. T h e a m o u n t o f NH,~ + - N in t h e s e t r e a t m e n t s d e c l i n e d to z e r o in t w o w e e k s with the Cabin Creek sludge treatments whereas three weeks were required for this v a l u e t o r e a c h z e r o w i t h t h e S o u t h R i v e r s l u d g e - t r e a t e d soils. T h e l o n g e r p e r s i s t e n c e o f N H , + - N at t h e h i g h r a t e o f S o u t h R i v e r s l u d g e w o u l d b e e x p e c t e d s i n c e n i t r i f i c a t i o n d u r i n g this p e r i o d was negligible. T h e ( N O 3 - + N O 2 - ) - N v a l u e s in T a b l e 3 s h o w t h a t t h e lag p h a s e was l o n g e r f o r t h e 16 m g / g r a t e t h a n e i t h e r t h e 1 o r 4 m g / g r a t e s o f C a b i n C r e e k sludge, W i t h t h e S o u t h R i v e r sludge, t h e lag p e r i o d i n c r e a s e d w i t h e a c h i n c r e a s i n g level o f sludge. T h e n e g a t i v e ( N O 3 - + N O 2 - ) - N v a l u e s a t t h e h i g h r a t e o f S o u t h R i v e r s l u d g e i n d i c a t e t h a t t h e v a l u e s f o r t h e s l u d g e - t r e a t e d soils w e r e less t h a n t h o s e f o r

79

N I T R I F I C A T I O N IN SOIL T R E A T E D W I T H S E W A G E S L U D G E

the untreated controls. In fact, the data in Fig. 2 show that no nitrification occurred in this treatment for the first two weeks of the experiment. A comparison of the NH4 + - N and ( N O 3 - + N O 2 - ) - N values for the 16 mg/g rates of the two sludges shows that nitrification was impaired to a much greater extent with the South River sludge than with the Cabin Creek sludge. The reason for this must be attributed to differences in the chemical composition of the two sludges. Possibly the organic fractions were different and some organic material was responsible for the lowered nitrification rates observed with the South River sludge. Using a liquid sludge, Premi & Cornfield (1969a) reported temporary inhibition of nitrification at rates of 0.2% (dry weight basis) and higher. They attributed this inhibition to organic constituents since amounts of Cu, Zn, Cr and Mn supplied by the sludge did not exceed 6-4/~g/g in the treated soil. Ryan et al. (1973) reported a similar inhibition in nitrification where high rates (940 and 1880 /lg/g N) of liquid sludge were used. They concluded that the toxic material could have been either organic or inorganic. TABLE 4 CONCENTRATION OF METALS IN AMENDED CABIN CREEK SLUDGE AND SOUTH RIVER SLUDGE

Elemental concentration (Itg/g)

Sludge Amended Cabin Creek South River

Mn

Zn

Cu

Cr

Cd

Pb

1050 1000

8330 9240

540 470

800 980

110 140

2450 2900

In the present study, no attempt was made to characterise the organic fraction of the sludge. However, the inorganic fraction and particularly the metal content of the two sludges were significantly different (Table 1). Since many metals are toxic at high concentrations it seemed probable that the reduction in nitrification observed at the high rate of South River sludge was due to metal toxicity. To test this hypothesis, a sample of the Cabin Creek sludge was amended with the chlorides of Mn, Zn, Cu, Cr, Cd and Pb to give final concentrations of these elements similar to those found in the South River sludge. Table 4 shows the final concentrations of these elements in the sludge as determined by analysis. For comparison, the values for these elements in the South River sludge are also shown. It can be seen that the concentrations were approximately the same in both sludges. The ( N O 3 - + N O 2 - ) N values for the incubated soils receiving the amended Cabin Creek sludge and 100 /~g/g NH4 + - N are shown in Fig. 3. The addition of these metals to the Cabin Creek sludge clearly resulted in lowered ( N O 3 - "F N O 2 - ) - N values at the highest rate compared with the unamended Cabin Creek sludge treatments. Nitrification in the amended sludge treatments was inhibited to an even greater extent than similar treatments receiving the South River sludge, although total metal concentrations were similar. This seems reasonable,

80

D . O . WILSON

Amended Cabin Creek Sludge

150

A

Control =¢ =J,

I

1 mg/g

.¢. _ _ _ . . , . . , - ~

If.." . . . . . . . . . . . .

........... 4 mg/g ~ 16 mg/g

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I.~A-:.. ":"

#,/' //

Z

+ !

J

=w,

:"

~....'"" ~ _ . ~

v

Fig. 3.

,*°

4J

50

..."

..':

z

I

0

1

|

I

I

2 3 4 TIME (Weeks)

I

I

5

6

Nitrification in soil receiving 100 ag/g NH4+ - N and the indicated rates of amended Cabin Creek sludge.

since metals supplied as inorganic salts are usually more biologically active than those forms associated with sludge (Cunningham 1975). The decrease in nitrification in the amended sludge treatment could have been caused by a lowering of pH as a consequence of the metal salt addition. Table 5 shows the pH values.of various treatments at the end of six weeks' incubation. The amended Cabin Creek sludge had the lowest pH values of all treatments. It is unlikely that pH differences of the magnitude found in this study could account for the observed inhibitory effects on nitrification with either the amended Cabin Creek sludge or the South River sludge. The original hypothesis that metal toxicity

et al.,

TABLE 5 PH VALUES OF TREATED AND UNTREATED SOIL AFTER INCUBATION FOR SIX WEEKS

Treatment Soil alone Soil with 16 mg/g Cabin Creek sludge Soil with 16 mg/g South River sludge Soil with 16 mg/g amended Cabin Creek sludge

NH4 +(ltg/g) -- N added

pH value

0 100 0 100 0 100 0 100

6-24 58O 5.95 5-93 6.07 5.73 5"84 5-54

NITRIFICATIONIN SOIL TREATED WITH SEWAGE SLUDGE

81

is the major factor responsible for inhibition of nitrification in the South River sludge treatments is substantiated by the results from the amended Cabin Creek sludge treatments. The South River sludge had a higher metal content than the Cabin Creek sludge (Table 1), but Zn was particularly high. Zinc is the metal most often present in greatest amounts in municipal sludges. The addition of 16 mg/g of this sludge increased the Zn level in the treated soil by 148/~g/g. Premi & Cornfield (1969b) reported that nitrification was unaffected, partially inhibited and totally inhibited by 100, I000 and 10,000 /~g/g Zn, respectively. Preliminary experiments in my laboratory show that nitrification in the soil used in the present work is temporarily inhibited by 100 pg/g Zn and totally by 1000/~g/g Zn. Using solution cultures, Loveless & Painter (1968) found that growth of pure cultures of Nitrosomonas europoea was inhibited at Zn levels as low as 0.08/tg/ml. Besides Zn, other elements are present at relatively high concentrations in the South River sludge when compared with the Cabin Creek sludge. Lead is nearly seven times higher and increases the Pb level in the 16 mg/g South River sludge treatment by 47 pg/g. Cadmium is also seven times higher in the South River sludge. It is also possible that the toxicity may be due not to a single element, but rather to a combination of several elements, but further definitive work is needed before exact causative agents cart be specified. The results of these experiments indicate that the application of high rates of sewage sludge containing high concentrations of metals may temporarily inhibit nitrification. Because of the low loss rate of most metals from soils, extended use of such sludges may seriously interfere with this important microbial N transformation in soil.

ACKNOWLEDGEMENT The capable technical assistance of Paul Mask, Helen Piercy and E. Vicki Berryman is greatly appreciated.

REFERENCES ALLISON,L. E. (1965). Organic carbon. In Methods of soil analysis, Part 2, (ed. by C. A. Black) 1367-78. Madison, Wisconsin, American Society of Agronomy. BOSWELL, F. C. (1975). Municipal sewage sludge and selected element applications to soil: Effect on soil and fescue. J. Environ. Qual., 4, 267-73. BREMNER,J. M. (1965a). Total nitrogen. In Methods of soil analysis, Part 2, (ed. by C. A. Black) 1149-78. Madison, Wisconsin, American Society of Agronomy. BREMNER,J. M. (1965b). Inorganic forms of nitrogen. In Methods of soil analysis, Part 2 (ed. by C. A. Black) 1179-237. Madison, Wisconsin, American Society of Agronomy. CLARK, K. G. & GADOY, V. L. (1955). Composition and nitrification characteristics of some sewage and industrial sludges--1952. Farm Chem., 118, 41-5.

82

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CUNNINGHAM, J. D., KEENEY, D. R. & RYAN, J. A. (1975). Phytotoxicity and uptake of metals added to soils as inorganic salts or in sewage sludge. J. Environ. Qual., 4, 460-2. KINC, L. D. (1973). Mineralization and gaseous loss of nitrogen in soil-applied liquid sewage sludge. J. Environ. Qual., 2, 356-8. KING, L. D. & MORRIS, H. D. (1972). Land disposal of liquid sewage sludge. I. The effect on the growth, chemical composition and in civo digestibility of Coastal bermudagrass (Cynodon dactylon L. Pers.). J. Environ. Qual., 1, 325-9. LOVELESS,J. E. & PAINTER, H. A. (1968). The influence of metal ion concentrations and pH value on the growth of a Nitrosomonas strain isolated from activated sludge. J. Gen. Mierobiol., 52, 1-14. MILNE, R. A. & GRAVELAND, D. N. (1972). Sewage sludge as a fertilizer. Can. J. SoilSci., 52, 270-3. MURPHY, J. & RILEY, J. P. (1962). A modified single solution method for the determination of phosphate in natural waters. Analytica chim. Acta, 27, 31-6. PREMI, P. R. & CORNFIELD, A. H. (1969a). Incubation study of nitrification of digested sewage sludge added to soil. Soil Biol. & Biochem., 1, I-4. PREMI, P. R. & CORNFIELD, A. H. (1969b). Effects of additions of copper, manganese, zinc and chromium compounds on ammonification and nitrification during incubation of soil. Pl. Soil, 31,345-52. PRE~I, P. R. & CORNVIELD, A. H. (1971). Incubation study of nitrogen mineralization in soil treated with dried sewage sludge. Environ. Polhtt., 2, I-4. RYAN, J. A., KEI~NEY,D. R. & WALSI-I,L. M. (1973). Nitrogen transformations and availability of an anaerobically digested sewage sludge in soil. J. Environ. Qual., 2, 489-92.