A STUDY ON POTENTIAL AGRICULTURAL USE OF SEWAGE SLUDGE OF ANKARA WASTEWATER TREATMENT PLANT


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A STUDY ON POTENTIAL AGRICULTURAL USE OF SEWAGE SLUDGE OF ANKARA WASTEWATER TREATMENT PLANT

Sevinç Arcak ¹ , Ayten Karaca ¹ , Emrah Erdoğan ¹ , Cafer Türkmen ²

¹ Soil Science Department, Faculty of Agriculture, Ankara University, Ankara
² Soil Science Department, Faculty of Agriculture, Çanakkale Onsekiz Mart University, Çanakkale

ABSTRACT

The plant nutrients nitrogen, phosphorus, and others present in smaller quantities, as well as organic matter, make sludge disposal on land an attractive option. Nitrogen has received most attention and it is normally the most abundant sludge nutrient. One of the best alternatives to waste disposal is through the soil-plant system as a fertilizer. Based on contrasting properties, different wastes can be co-recycled in order to take simultaneously the best profit and minimize environmental pollution. An experiment was carried out with a calcareous soil to which six different doses of a sewage sludge were treated. A crop barley (Hordeum vulgare L. 'Tokak-501') was grown in the amended soils. The application of sewage sludge to a calcareous soil lowered the pH of the soil, although the value was always around 7.75-7.91 at the end of the experiment. In the barley plants it was observed that the higher the yield, the higher the N contents. Electrical conductivity rose with organic amendment. As anticipated, such an amendment improved the nutritional level of the soils, particularly total N and available P.

INTRODUCTION

Sewage sludge is the insoluble residue from wastewater treatment after either aerobic or anaerobic digestion processes. Sludge comprises resistant organic compounds (60% organic matter), nitrogen (3%), phosphorus (2%, P2O5), other macronutrients (0.5% K2O, 5% CaO, 1.5% MgO), a wide range of macronutrient and nonessential trace metals, organic micropollutants, microorganisms and eggs of parasitic organisms. The substantial N and P concentrations in sludge render is a useful fertilizer material and its organic constituents give it beneficial soil conditioning properties. The improved aeration and drainage following sludge amendments can have indirect effects on the soil-plant relationships of heavy metals through affecting growth, nodulation in leguminous plants and other properties (Heckman et al., 1986; Roberts et al., 1988).

There is an increasing interest in the agricultural application of sludges obtained in wastewater treatment plants, due to the possibility of recycling valuable components; organic matter, N, P, and other plant nutrients (Sommers, 1977; Chaussod et al., 1978; Suss, 1979).

In general, it has been shown that the addition of sludge to agricultural land increases crop production. Dowdy et al. (1978) reported that the increase of crop yield by sludge application often exceed that of well-managed fertilized controls.

On the other hand, since sewage sludge contains high concentrations of potentially toxic elements such as Zn, Ni, Cd, and Cu problems way arise when sludge is applied to an agricultural soil (Sanders et al., 1986; Omran and Waly, 1988) and heavy metal accumulation in the plant tissues may also occur. The fertility benefit must be balanced against the potential hazards of metal contamination through application of sludge to agricultural productive land.

Sewage sludge produced in Ankara regions (Sincan-Tatlar Village) is used for the improvement of soil fertility and crop production. Therefore, studies on sludges are important due to the economic and environmental implications of widespread application of these materials to agricultural lands. There is no information available on fertilizer value of Ankara sewage sludge. This paper describes investigations into the fertilizer nitrogen and phosphorus value of Ankara sewage sludge using the pot experiments under greenhouse conditions.

MATERIALS and METHODS

Soil and Sludge Description:

The soil was used a clayey taken from the surface horizon of Sincan-Tatlar village near Ankara. The sludge was of the activated type and was municipal sewage sludge. The soil and sludge samples were air dried and crushed so as to pass a 2 mm sieve. The physical and chemical characteristics of the sludge and soil are shown in Table 1.

Experimental Design:

Each pot consisted of 5000g of coarsely sieved soil with various amendments.

Treatment I: Sludge nitrogen was compared with inorganic nitrogen (ammonium nitrate). Three replicates of each nitrogen treatment were assembled as follows:

     1. The control pots were unamended.
     2. Soils were supplemented with KH2PO4 to yield 40 ppm (N0, N0+S0, and S0).
     3. Soils were supplemented with KH2PO4 to yield 40 ppm and NH4NO3 to yield 30, 60, 120, 240, and 480 ppm (N1, N2, N3, N4, and N5)
     4. Soils were supplemented with KH2PO4 to yield 40 ppm and NH4NO3 to yield 15, 30, 60, 120, and 240 ppm and sewage sludge were added to soil at 5, 10, 20, 40, and 80 t ha-1 (N+S1, N+S2, N+S3, N+S4, and N+S5 ).
     5. Soils were supplemented with KH2PO4 to yield 40 ppm and sewage sludge were added to soil at 10, 20, 40, 80, 160, and 320 t ha-1 ,chosen to supply amounts of available N similar to the ammonium nitrate rates. (S1, S2, S3, S4, S5, and S6 ).

The pots were seeded with barley (Hardeum vulgare, L. 'Tokak-501'), 20 seed per pot and the plants were thinned 15 after germination. The water content of the soil was adjusted to 70% of field capacity. The pots were placed in greenhouse.

Sampling and Analysis:

Three months after seeding, the plants were harvested for nutrient composition and chemical analysis. Samples were analyzed for soil sample, pH and EC were measured in a 1:2.5 water extract (Richards, 1954); lime was determined according to Richards (1954); organic material by using modified Walkley-Black Method (Jackson, 1962); soil cation exchange capacity (CEC) was determined by saturation with ammonium acetate at pH 7 (Chapman, 1965). For plant, P was determined according to Kitson and Mellon (1944) and Borton (1948). K was determined by flame photometry (Johnson and Ulrich, 1959). For soil sample, available P was determined according to Olsen et al (1954) and the content determined by the Murphy and Riley method (Murphy and Riley, 1962). Total nitrogen was assessed using the Kjeldahl method, as specified by Bremner (1965). Soil samples were extracted for available Fe, Cu, Zn, Mn, Co, Ni, and Cd in DTPA solution (0.005M DTPA+0.005M CaCl2+0.1M TEA (triethanolamine) pH 7.3), (Lindsay and Norvell, 1978). All the solutions of Fe, Zn, Cu, Mn, Co, Ni, and Cd were analyzed by atomic absorption spectrophotometer (AAS) with flame or graphite furnace when required.

RESULTS and DISCUSSION

Table 2 shows dry matter production and the macronutrient contents in barley crops for the various treatments. It was observed that the application of sewage sludge enhanced soil fertility and that crop yield in the amended soils was higher than in the control. P and K were the macronutrients less absorbed by the barley crop. However, N was the macronutrients most absorbed when sludge was applied to soil. With sewage sludge, the low rate of application did not significantly change dry matter production on either of the soils. On the heavy textured soil, efficiency decreased with increasing rate of sludge.

It can be observed that the contents of total N in the soil increased when the sewage sludge added, the largest values of total N being recorded when the sludges were applied than that inorganic fertilizers. The application sewage sludge resulted in the largest increase of available P content. The amended soils, particularly those to which high doses at sludge (320 t ha-1) had been applied, showed a higher nitrogen and phosphorus content than the control (Table 2). Since the same amount of inorganic fertilizer was applied to the soils these differences could be attributed to the organic amendment. This phenomenon can be expected since sewage sludge contains both high quantities of proteinic material (Serna and Pomares, 1992), as can be seen from the high values for N in Table 2, and of polyphosphorated compounds from detergenints. The effects of sludge on barley potassium values were variable, but generally small.

The soil pH is of paramount importance in controlling the plant absorption of heavy metals since it conditions their mobility in soil. According to Pluquet (1984) an increase of one unit in pH reduces heavy metal absorption by plants by 14 %. When sewage sludge (whether or not contaminated by heavy metals) was applied, the soil pH decreased in all the cases, but fell by approximately half a unit when the maximum dosage (320 t ha-1) was used (Table 2). Electrical conductivity also varied when the sludge amendment was carried out and it increased compared to the control (Table 2) due to the formation of metallic salts (complexes of organic matter and heavy metals). EC of the maximum sludge amended soil was 4.48 times higher than the control. In the soil amended with sewage sludge (especially S5, and S6 dosages) the CEC content significantly increased. There was no significant differences between the control and CEC in nitrogen and nitrogen + sludge treatments. The amount of organic matter determined in the soil (Table 2) was not significantly different between the control and nitrogen treatment soils. But, significant difference in organic matter was found between the control and sludge amended soils.

In general, in terms of nutritional status, the amended soils at the end of the experiment showed higher N and P contents than the control soil, but a similar content of CEC, EC, confirming the theories proposed by several authors (Zucconi and Bertoldi, 1987). Thus the yield decrease caused by the organic amendments must be due to both, to the heavy metals contained in these materials and to the increased conductivity.

In conclusion, the sewage sludge used in this study was very poor sources of P for plant growth, primarily because Fe and Al treatments were used to precipitate P in the sludge P in these sludge was in organic form so microbial minerilization had little effect on P availability.

ACKNOWLEDGEMENTS

This project has been supported by TUBITAK through contract No: TOGTAG-1712.

REFERENCES

Arden, D.A. (1977). The agricultural use of sewage sludge. In: R.C. Loehr (ed.), Land as a waste management alternative. Springer-Verlag, Berlin, pp. 583-603.
Barton, C.J. (1948). Photometric analysis on phosphate rock. Ind Eng. Chem. Anal. ,Ed. 20: 1068-1073.
Bremner, J.M. (1965).Total nitrogen. In Methods of Soil Analysis Part 2; (C.a. Black, Ed),. American Society of Agronomy, Madison, Wis., 1145-1178.
Chapman, H.D. (1965). Methods of soil analysis Part 2. Chemical microbiological properties. Ed. C.A. Black. Amer. Soc. of Agron. Inc. Publ. Agron. Series no: 9, Medison, Wis, USA.
Chaussod, R., Germon, J.C., Catroux, G. (1978). Determination de la valeur fertilisante des boues residuaires. Aptutude a liberer l'azote. Ministe' re de l'environement et du cadre de vie. Convention d'etude n. 74050 (in French).
Dowdy, R.H., Larson, W.E., Titrud, J.M., Latterell, J.J. (1978). Growth and metal uptake of snap beans grown on sewage sludge amended soil. A four-year field study. J. Environ. Qual. 7: 252-257.
Heckman, J.R., Angle, J.S., Chaney, R.L. (1986). Soybean nodulation and nitrogen fixation on soil previously amended with sewage sludge. Biol. Fertil. Soils, 2: 181-185.
Heckman, J.R., Angle, J.S., Chaney, R.L. (1987). Residual effects of sewage sludge on soybean: I, Accumulation of heavy metals. J. Environ. Qual. 16: 113-114.
Jackson, M.L. (1962). Soil chemical analysis. Prentice Hall Inc. Eng. Cliffs. U.S.A..
Johnson, C.M., Ulrich, A. (1959). Analytical methods for use in plant analysis II. California Agri. Exp. Sta. Bull. 766.
Kitson, R.E., Mellon, M.G. (1944). Calorimetric determination of phosphorus as molybdovanadophoshoric acid. Ind. Eng. Chem. Analk., Ed. 16: 379-383.
Lindsay, W.L., Norwell, W.A. (1978). Development of a DTPA soil test for Zn, Fe, Mn and Cu. Soil Sci. Soc. Am. J. 42: 421-428.
Murphy and Riley (1962). A modified single solution method for the determination of phosphate in natural waters. Anal. Chem. Acta, 27: 31-36.
Olsen, S.R., Cole, V., Watanabe, F.S., Dean, L.B. (1954). Estimation of available phosphorus in soils by extraction with sodium bicarbonate. U.S. Dept. Of Agr. 939. Washingt, D.C.
Omran, M.S., Waly, T.M. (1988). Effect of sewage irrigation on yield, three components and heavy metals accumulation in navel orange trees. Biol. Wastes, 23: 17-24.
Pluquet, E. (1984). Die bodentung des tangehaltes und des pH-wertes fü die Schwermetaleufnahme einiger kuhurrflanzen aus kontaminierten bönen, UBA Texte 40, Berlin.
Richards, L.A., ed. (1954). Diagnosis and improvement of saline and alkali soils. U.S.D.A. Handbook 60.
Roberts, J.A., Daniels, W.L., Bell, J.C., Martens, D.C. (1988). Tall rescue production and nutrient status on southwest Virginia mine soils. J. Environ. Qual. 17: 55-62.
Sanders, J.R., Trevor, McM.A., Christensen, B.T. (1986). Extractability and bioavailability of Zn, Ni, Cd, and Cu in three Danish soils sampled 5 years after application of sewage sludge. J. Sci. Food Agric. 37: 1155-1164.
Serna, M.D., Pomares, F. (1992). Indexes of assessing N availability in sewage sludges. Plant Soil, 139: 15-21.
Sommers, L.E. (1977). Chemical composition of sewage sludge and analysis of their potential use as fertilizer. J. Environ. Qual. 6: 225-232.
Suss, A. (1979). Nitrogen availability in sewage sludge. In Concerted Action E.E.C. Treatment and Use of Sewage Sludge, Cost Project 68 bis, Dison.
Zucconi, F., De Bertoldi, M. (1987). Compost specifications for the production and characterization of compost from municipal solid waste. In compost: Production, quality and use, E.d. M. De Bertoldi, M.P. Ferranti, P.L. Hermite, Zucconi, F., p. 30-51, Elsveir Applied Science, New York.

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