Effects of domestic wastewater treated by anaerobic stabilization on ...

Environ Monit Assess (2016) 188: 664 DOI 10.1007/s10661-016-5680-x

Effects of domestic wastewater treated by anaerobic stabilization on soil pollution, plant nutrition, and cotton crop yield Nese Uzen & Oner Cetin & Mustafa Unlu

Received: 14 June 2016 / Accepted: 31 October 2016 / Published online: 12 November 2016 # Springer International Publishing Switzerland 2016

Abstract This study has aimed to determine the effects of treated wastewater on cotton yield and soil pollution in Southeastern Anatolia Region of Turkey during 2011 and 2012. The treated wastewater was provided from the reservoir operated as anaerobic stabilization. After treatment, suspended solids (28–60 mg/l), biological oxygen demand (29–30 mg/l), and chemical oxygen demand (71–112 mg/l) decreased significantly compared to those in the wastewater. There was no heavy metal pollution in the water used. There were no significant amounts of coliform bacteria, fecal coliform, and Escherichia coli compared to untreated wastewater. The cottonseed yield (31.8 g/plant) in the tanks where no commercial fertilizers were applied was considerably higher compared to the yield (17.2 g/plant) in the fertilized tanks where a common nitrogenous fertilizer was utilized. There were no significant differences between the values of soil pH. Soil electrical conductivity (EC) after the experiment increased from 0.8–1.0 to 0.9– 1.8 dS/m. Heavy metal pollution did not occur in the soil and plants, because there were no heavy metals in the treated wastewater. It can be concluded that treated domestic wastewater could be used to grow in a

N. Uzen (*) : O. Cetin Agricultural Faculty, Department of Agricultural Structure and Irrigation, Dicle University, Diyarbakir, Turkey e-mail: [email protected] M. Unlu Agricultural Faculty, Department of Agricultural Structure and Irrigation, Cukurova University, Balcali, Adana, Turkey

controlled manner crops, such as cotton, that would not be used directly as human nutrients. Keywords Anaerobic stabilization . Cotton . Domestic wastewater . Irrigation . Water quality . Soil pollution

Introduction Cotton is an important industrial crop in terms of fiber and oil. Cotton plays a significant role in the Turkish economy because Turkey is one of the top cotton producers in the world. In addition, the Southeastern Anatolia Region, where the study was carried out, has the highest growing area (56% of the cotton planted area in Turkey) (Anonymous 2013). Cotton yield is affected by environmental factors, genetic potential of the variety, and growing techniques. However, irrigation is the most important input for cotton growing, since cotton consumes much more irrigation water compared to other crops (Kanber et al. 1991; Cetin and Bilgel 2002). Because the study area has very low relative humidity, high temperature, and almost no rainfall during the growing season. The requirement of irrigation water for cotton is considerably high. On the other hand, considering industrialization, increasing population, climate change, and global warming in the world, fresh water resources decrease year by year. Consequently, one of the solutions is the use of marginal water resources such as domestic wastewater for irrigated agriculture. The use of wastewater in cotton irrigation might be, thus, considered. One of the

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advantages of the use of wastewater for cotton crops is that cotton is not directly placed in the food chain. On the other hand, there are many beneficial aspects of treated wastewater use in agriculture. These could be water shortage, disposing of large volumes of wastewater, devoting of high-quality water resources for potable uses, economic benefits, using of wastewater in terms of fertilizing, and soil fertility. In addition, availability of use of wastewater could be increased the choice of crops grown by farmers (Pescod 1992; Oron et al. 1995; Jiménez-Cisneros 1995; Biswas et al. 1999; Yadav et al. 2002). Irrigation with wastewater also provides the plants with low-cost nutrients, lowers the water constraints, and decreases the energy costs, resulting in lower carbon emission (Dawson and Hilton 2011). Kızıloglu et al. (2008) reported that treated wastewater could be used for irrigation of cabbage and other vegetables in case these are eaten cooked. However, monitoring of the wastewater quality to avoid contamination must be continuously performed. However, it also has negative impacts on environment and health due to overfertilization (Kalavrouziotis et al. 2008), pathogens (Kazmia et al. 2008), salts, and heavy metals (Li et al. 2008). Although application of the treated wastewater in irrigation of plants is a common practice worldwide (Angelakis et al. 1999), this practice is traditionally still affected by problems of public issues (Pollice et al. 2004; Menegaki et al. 2007; Alikhasi et al. 2012). Due to the fact that cotton plants do not placed directly to human nutrition, and it requires to be grown large volumes of irrigation water in the large fields, the use of treated domestic wastewater for cotton irrigation could provide some potential benefits. The aim of this study is to evaluate the effect of treated domestic wastewater on the pollution risks to soil, crop, and yield of cotton. In addition, it is to evaluate the effects of wastewater on plant nutrition.

Materials and methods Experimental site This research was carried out over 2 years at the Research Farm of Agricultural Faculty, Dicle University, Diyarbakır, Turkey in 2011 and 2012 growing season. The location of the experimental area is 37° 54′ N, 40° 14′ E at an elevation of 660 m above sea level. The

Environ Monit Assess (2016) 188: 664

soil texture at the experimental soil is clay. The climate of the site has typical terrestrial climatological characteristics. The average annual rainfall is 487 mm, and it occurs mainly during the months of winter and spring season. The average annual (growing season) and daily maximum evaporation from class A evaporation pan are 976 and 8.4 mm, respectively (Üzen 2014). The soil consists of 9% sand, 27% silt, and 64% clay in the top 0–30 cm. The bulk density ranged from 1.19 to 1.27 g cm−3 in the soil profile. The infiltration rate was 8 mm/h. There was no specific risk in terms of water table or soil salinity. The organic matter content, pH, and lime content of the soil were 1.67, 7.9, and 8.5%, respectively (Üzen 2014). Experimental tanks Metal tanks (containers) of 1.00 m height and 0.60 m diameter were used for the experiment. Soil was collected from the fields, dried, sifted through a sieve with an aperture of 6.35 mm, and pressed into tanks in layers of 5 cm considering the bulk density of soil in the fields. The bottom layers of the tanks were filled with 5 cm of sand–gravel mixture for drainage. The schematic picture of the experimental tanks is given in Fig. 1. Irrigation water resources In the experiment for irrigation, two different water resources, fresh water and treated domestic wastewater, were used. Fresh water was provided by a deep well. Treated wastewater was provided by the wastewater plant of Dicle University. Treatment method of wastewater The stabilization pond system is usually separated in two different stages (Pescod 1992). The first processing stage takes place in the anaerobic ponds (primary treatment). Thus, it is mainly designed to decrease the biochemical oxygen demand (BOD5) and to remove the organic and inorganic solids, greases, and oils (Feigin et al. 1991). The wastewater treatment plant in the university campus, for domestic purposes, was designed as an anaerobic stabilization reservoir. There were four reservoirs (pools) connected to each other. Average depth of the reservoirs is 4 m, with a rectangular section and 40 × 200 m each. Domestic wastewater comes into the


0.100m 0.20m 0.20 m 0.10m

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1.00 0m

0.60 m

Fig. 1 The schematic and picture of the experimental tanks

first pool and is linked in a series for improved treatment to accumulate sedimentation and other processing. At the end of this process, it is expected that the wastewater meets the threshold values required by the Regulation on Water Pollution Control of Turkey in terms of the minimum levels of pollutants. Then, this wastewater could be released to natural watersheds. The capacity of this treatment plant is 8160 m3/day. During the test period, influent wastewater flow rate ranged from 6.8–15.6 L/s.

The amount of irrigation water calculated according to the experimental treatments was applied to the tanks by means of a volumetric cap. Irrigation scheduling was based on class A evaporation pan (Kanber and Güngör 1986) and irrigation interval was set to 10 days. The volume of irrigation water was calculated based on the cumulative pan evaporation coefficient, Kpc = 1.00, during identified irrigation interval, surface area of the tank, and based on soil depth (0.90 m) (Cetın and Bilgel 2002). Water, plant, and soil analyses

Experimental treatments and agronomic applications This study was carried out in 2011 and 2012. Different treatments were applied for each experimental year. Thus, the study aimed to expose the distinctive effects of wastewater on providing nutrients for soil and crops. The split-plot design was used in a completely randomized design with four replications (Table 1). Recommended fertilizers and other treatments, 50% of the recommended fertilizer and no fertilizer, were also studied. This study, thus, aimed to determine the effects of wastewater on soil fertility and fertilizing. Cottonseeds were sown on May 20, 2011 and May 10, 2012. After the emergence of the plants, young plants were arranged using a row distance of 20 cm. Three plants were grown in each experimental tank. Appropriate fertilization for nitrogen phosphorus for the study area was recommended as 130 kg N/ha and 80 kg P2O5/ha under the farms’ conditions (Özer and Dagdeviren 1986; Karademir et al. 2005).

At the end of the study, analyses were made to determine the content of macro, micro, and some heavy metals in the soil due to fertilization and wastewater usage. Soil samples for the analysis were taken from two different depths (0–30 cm and 30–60 cm) of the tanks. Wastewater samples were collected for analysis before each irrigation cycle. These analyses were electrical conductivity (EC), pH, carbonate + bicarbonate, calcium + magnesium, sulfate, chloride, and sodium + potassium. Water quality and heavy metals were determined. In addition, BOD5, chemical oxygen demand (COD), suspended solids (SS), E. coli, enterococcus bacteria, and total fecal coliform counts were also analyzed. Total N, P, Ca, Mg, Fe, Zn, Mn, Cu, Al, Cd, Ni, Pb, and B in the plants were analyzed (Kacar and Inal 2008). Bulk density, field capacity, wilting point, pH and electrical conductivity, lime, organic matter, cation

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Table 1 The experimental treatments 2011

2012

Main treatments

Sub treatments

F1: recommended fertilizer (N, P) F2: no fertilizer

F1: recommended fertilizer I1: freshwater (100% of Ep) I0: freshwater (100% of class A evaporation pan, Ep) (N, P) I2: wastewater (100% of Ep) I1: wastewater (100% of Ep) F2: 50% of the I3: diluted wastewater (50% I2: wastewater (120% of Ep) recommended fertilizer wastewater + 50% freshwater) (100% of (N, P) Ep) I3: wastewater (80% of Ep) F3: no fertilizer I4: diluted wastewater (50% wastewater + 50% freshwater) (100% of Ep)

exchange capacity (CEC), and exchangeable sodium percentage (ESP) for the soils and water analyses (pH, EC, cations, and anions) were determined according to the principles given in Tüzüner (1990). Soil pH was determined through a pH meter (McNeal 1982). EC was determined through a conductivity meter. Total N was determined using the Kjeldahl procedure (Bremner and Mulvaney 1982). Concentrations of soluble Ca and Mg were found using the EDTA titration method, while Na and K were measured by applying a flame photometer (Richards 1954). Phosphorus was determined using the Olsen extraction (0.5 M NaHCO3) (Olsen and Sommers 1982) procedure. Statistical analysis and evaluation The statistical analysis was performed using the randomized design with four replications. Thus, the effects of the treatments on yield and yield components were revealed. Yield of cotton data was evaluated for a single plant, because there were only three plants in the experiment, and a tank container was used. All data were analyzed using a JUMP which is a statistical computer program. Variance analyses were made for each experimental year. Statistical evaluation of data was conducted under the principles given by Yurtsever (2011).

Results and discussion Fresh water properties Some analysis results for the fresh water are given in Table 2. Considering Water Pollution Control Regulation of Turkey quality standards, there are no problems

Main treatments

Sub treatments

in terms of irrigation applications. According to these regulations, the fresh water could be used appropriately for irrigation (Anonymous 2004).

Untreated wastewater properties The analysis results in biological, chemical, and heavy and trace elements of wastewater used in the experiment are given in Table 3. Biological analysis of the influent wastewater used in the experiment included SS, total fecal coliform, COD, BOD5, coliform, E. coli, and enterococcus bacteria count. Suspended solids and fecal coliform ranged from 64 to 97 mg/l and 1199 in 2011 and 2012, respectively. Considering the values of COD, the minimum and maximum values were 0.01 and 110.2 mg/l, respectively. In the samples of wastewater on September 12, 2012, the value of BOD5 was 37.3 mg/l, whereas the sample collected on September 6, 2011 resulted in 58.0 mg/l. Considering these results, this wastewater should not be used without any treatment for Table 2 Chemical properties of fresh irrigation water Parameters

Fresh water

pH

8.0

EC (mmhos cm−1)

622

Ammonium (mg l−1)

–

Calcium (mg l−1)

18.4

Magnesium (mg l−1)

16.5

Sodium (mg l−1)

93.8

Potassium (mg l−1)

1.8

Chloride (mg l−1)

22.0

Sulfate (meq l−1)

4.0


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Table 3 Some properties of the untreated wastewater Properties

Parameters

Sampling dates 06.09.2011 12.09.2012

Biological parameters

Chemical parameters

Heavy metals– trace elements

SS (mg l−1)

97

64

Enterococcus (Kob ml−1) Coliform bacteria (Kob ml−1) Fecal coliform (EMS ml−1) E. coli (Kob 100 ml−1) BOD (mg l−1)

–

–

1.1 × 103

1.5 × 103

1100