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Applied Water Science

, Volume 7, Issue 5, pp 2385–2396 | Cite as

The assessment of treated wastewater quality and the effects of mid-term irrigation on soil physical and chemical properties (case study: Bandargaz-treated wastewater)

Open Access
Original Article

Abstract

This study was conducted to investigate the characteristics of inflow and outflow wastewater of the Bandargaz wastewater treatment plant on the basis of the data collection of operation period and the samples taken during the study. Also the effects of mid-term use of the wastewater for irrigation (from 2005 to 2013) on soil physical and chemical characteristics were studied. For this purpose, 4 samples were taken from the inflow and outflow wastewater and 25 quality parameters were measured. Also, the four soil samples from a depth of 0–30 cm of two rice field irrigated with wastewater in the beginning and middle of the planting season and two samples from one adjacent rice field irrigated with fresh water were collected and their chemical and physical characteristics were determined. Average of electrical conductivity, total dissolved solids, sodium adsorption ratio, chemical oxygen demand and 5 days biochemical oxygen demand in treated wastewater were 1.35 dS/m, 707 ppm, 0.93, 80 ppm and 40 ppm, respectively. Results showed that although some restrictions exist about chlorine and bicarbonate, the treated wastewater is suitable for irrigation based on national and international standards and criteria. In comparison with fresh water, the mid-term use of wastewater caused a little increase of soil salinity. However, it did not lead to increase of soil salinity beyond rice salinity threshold. Also, there were no restrictions on soil in the aspect of salinity and sodium hazard on the basis of many irrigated soil classifications. In comparison with fresh water, the mid-term use of wastewater caused the increase of total N, absorbable P and absorbable K in soil due to high concentration of those elements in treated wastewater.

Keywords

Bandargaz Irrigation Soil Treatment Wastewater 

Introduction

Today, due to the constraint in availability of the freshwater for irrigation, wastewater especially sewage water is being used for irrigation of agriculture fields (Singh et al. 2012). Specially, in arid and semi-arid regions, irrigation water shortage turns treated wastewater into an attractive source of water for irrigated agriculture (Pescod 1992). Hamilton et al. (2007) reported that globally around 20 million ha of land were irrigated with reclaimed wastewater, and the amount would increase markedly during the next few decades as water stress intensifies (after Chen et al. 2013c). However, Chen et al. (2015a) reported in spite of poor general public’s knowledge on water resources, their awareness on reclaimed water reuse was high. Moreover, some of the stakeholders had concerns about the potential risks from reclaimed wastewater reuse.

Several studies have been done to investigate the possibility of using treated wastewater for irrigation. For example, Torabian and Motallebi (2003) in addition to evaluating the wastewater quality of EKBATAN treatment plant presented the plan of wastewater reuse management. Ghasemi and Danesh (2012) studied the wastewater samples from Mashhad treatment plant and stated that according to Ayers and Westcot Guide (1985), wastewater can be used for irrigation of agricultural land. Results of Hasanli and Javan (2006) and Salehi et al. (2008) showed that the application of treated wastewater for irrigation of green and afforestation species is possible.

As an irrigation water resource, reclaimed water from sewage treatment plants can provide soils with the nutrients and organic matter, ameliorating health conditions (biodegradable organic matter and beneficial microorganisms), soil biological activities and thus promote soil quality and sustainability. However, reclaimed water also contains nonessential toxic elements and most noticeably salts, which may lead to soil salt levels intolerable to most landscape plants or crops, especially in heavy soil (Chen et al. 2013a, b, 2015b; Lyu and Chen 2016). Moreover, the greatest health concern in using reclaimed wastewater for irrigation is directed to pathogens (Chen et al. 2013a). Wang et al. (2013) reported that concentration of some aroma chemical components (HHCB and AHTN) can be significantly increased in reclaimed wastewater-irrigated soils, although it would take 243 and 666 years for their accumulation in soils to reach the levels that harm the ecosystem and soil biota such as germinating plants and earthworms.

Assouline and Narkis (2011) stated that treated wastewater application will differently affect different zones in the soil profile, depending on irrigation management parameters and plant uptake characteristics. Results of Singh and Agrawal (2012) showed that wastewater irrigation led to beneficial changes in physico-chemical and biological properties of the soil. Generally, wastewater application for irrigation will lead to the reduction of soil porosity and consequently decrease in water retention (Aiello et al. 2007), decrease of saturated hydraulic conductivity (Aiello et al. 2007; Assouline and Narkis 2011), reduction of soil infiltration rate (Rohani Shahraki et al. 2006; Assouline and Narkis 2011), increase the soil contamination to heavy metals (Hoseinpoor et al. 2008; Singh and Agrawal 2012; Chen et al. 2013c), increase of soil salinity (Taghvaiian et al. 2008; Hoseinpoor et al. 2008; Chen et al. 2013b; Lyu and Chen 2016), increase of soil water retention (Taghvaiian et al. 2008), decrease of soil bulk density (Rohani Shahraki et al. 2006), increasing risks of nutrient imbalances and groundwater contamination of nitrate with irrational managements of reclaimed water (Candela et al. 2007) and increase of soil surface microbial contamination and concentrations of some pathogens like viruses and Giardia (Aiello et al. 2007; Levantesi et al. 2010). However, there is no consistency as reclaimed urban wastewater impacts were dependent on the quality of reclaimed water, irrigation rate and practices, irrigation period, soil properties, influent water characteristics, treatment process, crop characteristics and local climate conditions (Pereira et al. 2012; Chen et al. 2015b).

Irrigation water scarcity in the summer season in Bandargaz region, which coincides with the peak crop water requirement period, result in farmers interest to use treated wastewater as an unconventional water resource. Since a few years, farmers in the Bandargaz region used the treated wastewater for irrigation, this study was conducted to investigate the characteristics of inflow and outflow wastewater of the Bandargaz wastewater treatment plant and the effects of mid-term use of the wastewater for irrigation on soil physical and chemical characteristics.

Materials and methods

Bandargaz City with an area exceeding 239.3 km2 is located in the west at a distance of 40 km from the center of Golestan Province (Gorgan). The direct distance of Bandargaz wastewater treatment plant from the sea is about 1.7 km and the distance where the wastewater discharged into the sea from the Miankaleh protected area is 35 km (Fig. 1). Origin of the raw wastewater is domestic and municipal. Secondary treatment method in the Bandargaz plant is aerated lagoons. This plant with a capacity of 3,100 m3/day was launched in 2005 (however, quality and quantity data in wastewater plant were gathered from 2007). Wastewater using concrete pipe reached the natural earth channels and then emptied into the sea (Fig. 1). Within the last 9 years, farmers have removed the manhole doors and pumped the treated wastewater to agricultural lands.
Fig. 1

Location of Bandargaz wastewater plant related to sea and Miankaleh protected area

In the study area, rice cultivation is dominant and irrigation season is approximately 2.5–3 months (mid-May–mid-August) along with peak of irrigation water requirement within July. In other month of year, treated wastewater is discharged to the sea.

To evaluate influent and effluent quality characteristics of wastewater, some parameters that were measured in the Bandargaz plant laboratory (from 2007 until 2012) were obtained. These parameters include biological oxygen demand (BOD5), chemical oxygen demand (COD), settlement solids (SS) and discharge (Q). One sample in month was taken by wastewater treatment plant. Data normality was evaluated by one-sample Kolmogorov–Smirnov test (Smirnov 1948). Calculation of some descriptive statistics, data analyses of variance and means comparison (by least significant difference test at 5 % statistical level) were carried out using SPSS 16.0 package (Gomez and Gomez 1984).

Also, water samples were taken in two stages during month of July 2013 (an interval of 20 days) and 25 quality parameters including pH, total dissolved solids (TDS), electrical conductivity (EC), chloride, ammonia, nitrate, nitrite, phosphate, sulfate, total hardness (TH), total alkalinity, turbidity, potassium, calcium, magnesium, sodium, bicarbonate, carbonate, hydroxide alkalinity, BOD5, COD, total solids, total suspended solids (TSS), total coliform and fecal coliform were measured. To assess the feasibility of usage of wastewater for irrigation, wastewater effluent quality was compared with standards for irrigation water quality. Since farmers in the area surrounding the plant from the beginning of its operation (from 2005) were using treated wastewater for irrigation, the effects of its usage on soil characteristics were evaluated. For this reason, soil samples were collected before of summer crop season and its middle (May and July, respectively) from 0–30 cm depth. Two rice fields irrigated with wastewater and one adjacent field irrigated with fresh water were selected. Then, soil physical and chemical properties including EC, pH, calcium, magnesium, sodium, bicarbonate, carbonate, sodium adsorption ratio (SAR), residual sodium carbonate (RSC), exchangeable sodium percentage (ESP), organic carbon, total nitrogen, phosphorus, potassium and clay, silt and sand percentage of soil (soil texture) were measured. Soil infiltration was measured using double rings methods in three replications. Total wastewater and soil properties were measured based on APHA (2012) and Klute (1986), respectively.

Results and discussion

Assessment of influent and effluent wastewater

The results showed that all parameters were normal based on one-sample Kolmogorov–Smirnov test. Some descriptive statistics of BOD5, COD, SS and discharge (Q) of influent and effluent wastewater based on monthly and yearly average are shown in Tables 1 and 2, respectively. Based on design criteria of Bandargaz wastewater plant, BOD5 and SS of effluent wastewater should be less than or equal to 170 and 205 mg/l, respectively. Tables 1 and 2 showed that in all months and years, means of BOD5 and SS of effluent wastewater were less than design criteria. However, in all years and approximately in all months, wastewater discharge (Q) was greater than plant capacity (3,100 m3/day). It was due to the entrance of surface runoff to the wastewater collection network and street washing that led to chemical dilution of wastewater.
Table 1

Some descriptive statistics of influent and effluent wastewater based on monthly average

Month

Parameter

BODin

BODout

CODin

CODout

SSin

SSout

Q

1

Mean

119.5

23.0

233.0

48.1

150.1

21.1

4,091.3

SD

46.8

10.2

96.4

16.1

52.1

6.1

1,956.7

Std. error of mean

19.1

4.1

39.4

6.6

21.3

2.5

798.8

Minimum

45.0

15.0

57.0

25.0

55.0

15.5

600.0

Maximum

178.4

42.0

324.7

71.7

197.3

30.3

5,999.0

Range

133.4

27.0

267.7

46.7

142.3

14.8

5,399.0

Variance

2,189.6

103.1

9,294.6

259.1

2,713.5

37.8

3,828,630.7

% of total sum

7.4

8.2

7.8

8.4

7.5

10.4

9.6

2

Mean

118.1

21.6

230.5

44.8

148.7

16.1

3,733.3

SD

40.6

9.6

86.4

15.0

43.0

3.5

1,590.8

Std. error of mean

16.6

3.9

35.3

6.1

17.6

1.4

649.5

Minimum

65.0

13.5

85.0

23.0

75.0

11.0

650.0

Maximum

175.2

39.2

325.3

67.1

195.0

20.5

5,059.4

Range

110.2

25.7

240.3

44.1

120.0

9.5

4,409.4

Variance

1,646.1

91.8

7,468.6

225.9

1,848.8

12.4

2,530,749.2

% of total sum

7.3

7.7

7.7

7.8

7.4

7.9

8.8

3

Mean

132.8

23.6

232.0

46.7

140.5

15.9

3,206.1

SD

38.8

8.3

89.6

11.4

42.3

6.0

1,263.9

Std. error of mean

15.8

3.4

36.6

4.6

17.3

2.4

516.0

Minimum

66.0

13.8

82.0

35.0

75.0

8.5

700.0

Maximum

173.0

37.2

326.4

64.0

185.5

25.0

4,073.3

Range

107.0

23.4

244.4

29.0

110.5

16.5

3,373.3

Variance

1,506.1

68.8

8,019.8

129.3

1,792.8

36.0

1,597,529.4

% of total sum

8.2

8.4

7.8

8.1

7.0

7.9

7.5

4

Mean

138.7

20.6

238.7

43.7

151.7

20.6

2,948.6

SD

46.1

9.9

84.4

17.8

41.3

14.7

1,145.4

Std. error of mean

18.8

4.0

34.5

7.3

16.9

6.0

467.6

Minimum

60.0

10.0

90.0

13.0

75.0

10.9

700.0

Maximum

188.0

37.6

333.4

66.6

192.5

50.0

3,851.0

Range

128.0

27.6

243.4

53.6

117.5

39.2

3,151.0

Variance

2,122.4

97.7

7,123.2

317.5

1,707.8

217.0

1,312,043.8

% of total sum

8.6

7.3

8.0

7.6

7.6

10.2

6.9

5

Mean

144.2

22.6

250.7

50.1

143.0

13.4

2,879.5

SD

39.9

7.5

74.5

8.8

71.3

7.9

775.2

Std. error of mean

16.3

3.1

30.4

3.6

29.1

3.2

316.5

Minimum

76.5

14.4

123.5

37.6

1.1

0.0

1,626.0

Maximum

182.6

34.4

336.4

63.9

192.7

22.0

3,747.7

Range

106.1

20.0

212.9

26.3

191.6

22.0

2,121.7

Variance

1,591.2

56.1

5,543.1

77.3

5,090.3

62.0

600,977.4

% of total sum

8.9

8.0

8.4

8.7

7.1

6.6

6.8

6

Mean

145.7

24.1

245.3

49.1

141.4

14.5

2,864.4

SD

43.4

8.1

82.6

11.1

71.6

8.5

943.4

Std. error of mean

17.7

3.3

33.7

4.5

29.2

3.5

385.1

Minimum

78.0

12.8

95.0

30.0

1.5

0.0

1,445.0

Maximum

198.2

33.8

334.1

61.9

204.4

24.3

3,815.0

Range

120.2

21.0

239.1

31.9

202.9

24.3

2,370.0

Variance

1,886.9

64.9

6,830.6

122.5

5,126.9

71.5

889,983.2

% of total sum

9.0

8.6

8.2

8.6

7.1

7.2

6.7

7

Mean

143.6

23.6

247.5

46.2

139.4

13.5

3,169.9

SD

52.5

9.5

90.3

14.3

73.0

8.3

1,331.6

Std. error of mean

21.4

3.9

36.9

5.8

29.8

3.4

543.6

Minimum

63.0

14.0

89.0

19.0

0.3

0.0

1,186.0

Maximum

206.0

39.8

333.9

56.6

211.0

19.8

5,082.1

Range

143.0

25.8

244.9

37.6

210.7

19.8

3,896.1

Variance

2,751.6

90.2

8,162.1

204.5

5,335.3

68.7

1,773,072.9

% of total sum

8.9

8.4

8.3

8.0

7.0

6.7

7.4

8

Mean

152.0

27.8

258.4

49.2

315.3

13.1

3,498.5

SD

43.0

14.6

71.4

13.0

357.9

8.7

1,074.9

Std. error of mean

17.6

5.9

29.2

5.3

146.1

3.5

438.8

Minimum

80.5

11.4

136.3

26.0

135.5

0.0

2,009.0

Maximum

204.8

46.6

335.4

64.6

1,044.0

21.0

4,787.2

Range

124.3

35.2

199.2

38.6

908.5

21.0

2,778.2

Variance

1,848.9

212.2

5,100.8

168.3

128,125.3

75.3

1,155,468.6

% of total sum

9.4

9.9

8.7

8.6

15.7

6.5

8.2

9

Mean

141.7

27.3

254.8

49.7

164.5

17.9

4,107.7

SD

30.7

12.7

63.0

6.5

27.8

3.1

1,092.9

Std. error of mean

12.6

5.2

25.7

2.7

11.4

1.3

446.2

Minimum

87.4

14.2

174.3

39.0

130.8

14.8

3,150.8

Maximum

171.6

49.4

321.7

58.0

214.2

23.3

5,832.1

Range

84.2

35.2

147.5

19.0

83.4

8.5

2,681.3

Variance

945.3

161.9

3,968.7

42.2

773.6

9.5

1,194,324.6

% of total sum

8.7

9.7

8.5

8.7

8.2

8.8

9.6

10

Mean

127.4

24.9

266.6

47.7

162.9

16.9

3,740.1

SD

64.2

12.0

50.7

9.9

27.7

3.6

909.0

Std. error of mean

26.2

4.9

20.7

4.1

11.3

1.5

371.1

Minimum

16.0

12.6

180.6

33.8

141.0

12.9

2,432.0

Maximum

190.8

47.2

310.3

59.6

215.2

23.0

5,137.3

Range

174.8

34.6

129.7

25.8

74.2

10.1

2,705.3

Variance

4,120.3

143.1

2,569.6

98.8

766.8

12.7

826,254.1

% of total sum

7.9

8.9

8.9

8.3

8.1

8.4

8.8

11

Mean

131.4

22.4

264.7

48.6

172.5

21.0

4,002.9

SD

36.5

12.4

42.0

8.7

27.7

8.4

1,135.0

Std. error of mean

14.9

5.1

17.2

3.5

11.3

3.4

463.4

Minimum

73.0

11.3

193.2

37.8

135.0

10.5

2,500.0

Maximum

171.6

45.4

309.9

61.1

216.0

32.0

5,809.0

Range

98.6

34.1

116.7

23.3

81.0

21.5

3,309.0

Variance

1,329.0

154.9

1,766.3

75.0

769.0

71.1

1,288,308.8

% of total sum

8.1

8.0

8.9

8.5

8.6

10.4

9.4

12

Mean

126.1

19.5

259.8

50.4

172.8

18.6

4,384.1

SD

36.8

7.6

42.0

7.2

30.1

4.4

1,022.3

Std. error of mean

15.0

3.1

17.1

3.0

12.3

1.8

417.4

Minimum

60.3

10.7

204.3

44.4

133.5

13.2

3,483.8

Maximum

162.0

30.3

309.3

63.1

216.7

25.0

6,271.1

Range

101.7

19.6

105.0

18.7

83.2

11.8

2,787.3

Variance

1,354.1

58.3

1,760.1

52.5

906.7

19.5

1,045,178.4

% of total sum

7.8

6.9

8.7

8.8

8.6

9.2

10.3

Total

Mean

135.1

23.4

248.5

47.9

166.9

16.9

3,552.2

SD

41.8

9.9

70.1

11.4

114.4

7.6

1,238.7

Std. error of mean

4.9

1.2

8.3

1.3

13.5

0.9

146.0

Minimum

16.0

10.0

57.0

13.0

0.3

0.0

600.0

Maximum

206.0

49.4

336.4

71.7

1,044.0

50.0

6,271.1

Range

190.0

39.4

279.4

58.7

1,043.7

50.0

5,671.1

Variance

1,750.4

97.3

4,913.8

129.1

13,076.8

57.1

1,534,365.1

% of total sum

100.0

100.0

100.0

100.0

100.0

100.0

100.0

Unit of biological oxygen demand (BOD), chemical oxygen demand (COD) and settlement solids (SS) is mg/l and discharge (Q) is m3/day. Influent and effluent wastewaters are shown by in and out subscripts

Table 2

Some descriptive statistics of influent and effluent wastewater based on yearly average

Year

Parameter

BODin

BODout

CODin

CODout

SSin

SSout

Q

2007

Mean

77.4

14.7

125.8

30.3

155.6

18.6

1,749.5

SD

19.3

4.0

50.5

9.3

284.8

15.7

1,097.7

Std. error of mean

5.6

1.1

14.6

2.7

82.2

4.5

316.9

Minimum

45.0

10.0

57.0

13.0

0.3

0.0

600.0

Maximum

114.0

25.0

204.3

44.5

1,044.0

50.0

3,991.0

Range

69.0

15.0

147.3

31.5

1,043.7

50.0

3,391.0

Variance

370.8

15.8

2,551.9

86.2

81,122.1

245.4

1,204,982.3

% of total sum

9.5

10.5

8.4

10.6

15.5

18.4

8.2

2008

Mean

136.0

16.2

255.5

44.0

139.9

12.7

3,233.4

SD

15.5

2.5

36.3

6.8

9.1

4.7

767.0

Std. error of mean

4.5

0.7

10.5

2.0

2.6

1.4

221.4

Minimum

110.0

12.3

203.0

34.0

124.5

4.8

1,998.0

Maximum

152.4

20.4

294.8

54.5

151.1

19.3

4,409.0

Range

42.4

8.2

91.8

20.5

26.6

14.6

2,411.0

Variance

239.6

6.5

1,320.8

46.6

83.5

22.4

588,291.7

% of total sum

16.8

11.5

17.1

15.3

14.0

12.6

15.2

2009

Mean

158.9

33.1

301.8

53.4

165.5

15.6

3,741.4

SD

14.0

11.9

5.9

6.3

10.2

4.9

580.2

Std. error of mean

4.0

3.4

1.7

1.8

3.0

1.4

167.5

Minimum

123.4

18.4

293.0

44.6

152.0

8.5

2,967.0

Maximum

172.4

49.4

310.8

63.1

185.5

24.3

4,809.4

Range

49.0

31.0

17.8

18.5

33.5

15.8

1,842.4

Variance

195.1

142.7

34.4

39.3

104.6

23.7

336,670.8

% of total sum

19.6

23.5

20.2

18.6

16.5

15.4

17.6

2010

Mean

144.5

31.0

311.8

56.7

172.0

19.6

4,853.6

SD

58.6

11.0

39.2

11.5

10.6

3.9

969.5

Std. error of mean

16.9

3.2

11.3

3.3

3.1

1.1

279.9

Minimum

16.0

10.7

219.2

40.0

142.1

12.9

3,558.7

Maximum

179.4

44.2

336.4

71.7

186.5

30.3

6,271.1

Range

163.4

33.5

117.2

31.7

44.4

17.4

2,712.4

Variance

3,439.4

121.8

1,533.1

132.8

112.7

15.0

940,010.5

% of total sum

17.8

22.1

20.9

19.7

17.2

19.4

22.8

2011

Mean

162.6

19.8

241.9

48.8

170.0

15.9

3,668.2

SD

41.2

3.3

35.5

3.1

9.8

1.1

876.2

Std. error of mean

11.9

1.0

10.2

0.9

2.8

0.3

252.9

Minimum

86.2

14.8

182.2

45.2

164.8

14.6

2,970.4

Maximum

206.0

26.2

297.5

57.5

196.5

18.7

5,702.3

Range

119.8

11.4

115.3

12.4

31.7

4.1

2,731.9

Variance

1,698.8

11.2

1,258.3

9.7

95.8

1.1

767,799.1

% of total sum

20.1

14.1

16.2

17.0

17.0

15.7

17.2

2012

Mean

131.2

25.7

254.0

53.9

198.5

18.8

4,067.1

SD

12.6

2.6

31.5

2.7

28.6

4.8

468.3

Std. error of mean

3.6

0.7

9.1

0.8

8.3

1.4

135.2

Minimum

103.6

20.4

195.8

49.7

112.9

14.9

3,478.0

Maximum

147.0

28.8

287.3

58.0

216.7

32.0

4,998.4

Range

43.4

8.4

91.5

8.3

103.8

17.1

1,520.4

Variance

157.8

6.6

993.9

7.3

819.2

23.4

219,335.8

% of total sum

16.2

18.3

17.0

18.8

19.8

18.6

19.1

Total

Mean

135.1

23.4

248.5

47.9

166.9

16.9

3,552.2

SD

41.8

9.9

70.1

11.4

114.4

7.6

1,238.7

Std. error of mean

4.9

1.2

8.3

1.3

13.5

0.9

146.0

Minimum

16.0

10.0

57.0

13.0

0.3

0.0

600.0

Maximum

206.0

49.4

336.4

71.7

1,044.0

50.0

6,271.1

Range

190.0

39.4

279.4

58.7

1,043.7

50.0

5,671.1

Variance

1,750.4

97.3

4,913.8

129.1

13,076.8

57.1

1,534,365.1

% of total sum

100.0

100.0

100.0

100.0

100.0

100.0

100.0

Unit of biological oxygen demand (BOD), chemical oxygen demand (COD) and settlement solids (SS) is mg/l and discharge (Q) is m3/day. Influent and effluent wastewaters are shown by in and out subscripts

Assessment of influent and effluent wastewater based on analysis of variance of wastewater plant data is presented in Table 3. Month had significant effect on any parameters. In other words, means of all parameters had not significant differences in different months. However, year factor affected all parameters significantly, except influent and effluent SS. The results of yearly means comparison are presented in Table 4. Approximately, maximum values of all parameter were obtained in 2009–2010 and these values were increased since 2007–2010. This shows that there is probably poor performance of plant because of some operation difficulties.
Table 3

The results of analysis of variance for plant influent and effluent wastewater data

Source of variations

df

BODin

BODout

CODin

CODout

SSin

SSout

Q

Mean square

Sig.

Mean square

Sig.

Mean square

Sig.

Mean square

Sig.

Mean square

Sig.

Mean square

Sig.

Mean square

Sig.

Monthly

 Between

11

711

0.96

36

0.98

986

0.99

27.6

0.99

13,970

0.39

52.96

0.53

1,702,483

0.35

 Within

60

1941

109

5634

147.8

12,913

57.80

1,503,543

Yearly

 Between

5

11,432

0.00

712

0.00

52,853

0.00

1126

0.00

4,547

0.89

82.1

0.21

12,860,000

0.00

 Within

66

1017

51

1282

53.6

13,723

55.2

676,182

Unit of biological oxygen demand (BOD), chemical oxygen demand (COD) and settlement solids (SS) is mg/l and discharge (Q) is m3/day. Influent and effluent wastewaters are shown by in and out subscripts

Table 4

The results of yearly means comparison for plant influent and effluent wastewater data

Year

BODin

BODout

CODin

CODout

SSin

SSout

Q

2007

77.4d

14.7c

125.8c

30.3d

155.6a

18.6ab

1,749.5d

2008

136.0bc

16.2c

255.5b

44.0c

139.9a

12.7b

3,233.4c

2009

158.9ab

33.1a

301.8a

53.4ab

165.5a

15.6ab

3,741.4bc

2010

144.5abc

31.0ab

311.8a

56.7a

172.0a

19.6a

4,853.6a

2011

162.6a

19.8c

241.9b

48.8bc

170.0a

15.9ab

3,668.2bc

2012

131.2c

25.7b

254.0b

53.9ab

198.5a

18.8a

4,067.1b

In each column, means followed by at least one letter were not significantly different at the 5 % probability level (LSD test). Unit of biological oxygen demand (BOD), chemical oxygen demand (COD) and settlement solids (SS) is mg/l and discharge (Q) is m3/day. Influent and effluent wastewaters are shown by in and out subscripts

Quality parameters of four samples that were taken from the inflow and outflow wastewater are shown in Table 5. Comparing BOD5 values of influent and effluent samples (Table 5) with maximum and minimum values in July (Table 1) and total years (Table 2) showed that approximately sample values were located in the range of wastewater quality variations. However, COD values had some deviations from yearly and monthly ranges.
Table 5

Values of quality parameters of plant influent and effluent wastewater

No.

Parameter

Unit

Influent

Effluent

Sample 1

Sample 2

Average

Sample 1

Sample 2

Average

1

pH

7.25

7.24

7.25

7.69

7.77

7.73

2

TDS

ppm

671.5

629

650

664

749

707

3

EC

μs/cm

1,304

1,527

1,416

1,289

1,405

1,347

4

Cl

ppm

770

740

755

790

880

835

5

NH3

ppm

23

43

33.00

34.5

30

32.25

6

NO3

ppm

0.2

1.4

0.80

2.4

2.48

2.44

7

NO2

ppm

0.27

0.2

0.24

0.4

0.36

0.38

8

PO4

ppm

5.6

10.5

8.05

10.5

7

8.75

9

SO4

ppm

90

10

50

10

20

15

10

TH

ppm CaCO3

200

400

300

550

420

485

11

TA

ppm CaCO3

700

850

775

600

580

590

12

Turbidity

NTU

36

105

71

26

34

30

13

K

ppm

26

76.8

51.4

90

54

72.0

14

Ca

ppm

140

310

225.0

460

248

354.0

15

Mg

ppm

38.9

21.9

30.4

21.9

41.8

31.9

16

Na

ppm

85

63

74.0

71

42.1

56.6

17

CO3

ppm

420

510

465.0

360

353.8

356.9

18

HCO3

ppm

427

518.5

472.8

366

348

357.0

19

HA

ppm

150

300

225

300

160

230

20

COD

ppm

90

240

165

60

100

80

21

BOD5

ppm

49

132

91

33

55

44

22

TS

ppm

676

870

773

687

589

638

23

TSS

ppm

15.6

325.2

170.4

28.4

29.6

29.0

24

Total coliform

Count in 100 mL

More than 1100

More than 1100

More than 1100

More than 1100

210

Incomputable

25

Fecal coliform

Count in 100 mL

More than 1100

More than 1100

More than 1100

More than 1100

150

Incomputable

TDS total dissolved solids, EC electrical conductivity, TH total hardness, TA total alkalinity, HA hydroxide alkalinity, COD chemical oxygen demand, BOD 5 5 days biological oxygen demand, TS total solids, TSS total suspended solids

One of the major concerns regarding reclaimed water irrigation is on salinity (Chen et al. 2013b). Classification of Bandargaz-treated wastewater based on United State Salinity Laboratory (USSL) (Richards 1954; Wilcox 1955) was C3S1 that represents water with high salinity and without sodium hazard. However, it was C3 based on Richards (1954) that is suitable for salt-tolerant crop. The results showed that based on Ayers and Westcot Guide (1985), Bandargaz-treated wastewater is suitable for irrigation except for chlorine sensitive crops (Table 6).
Table 6

Assessment of effluent-treated wastewater based on Ayers and Westcot Guide (1985)

Category

Parameter

Unit

Sample 1

Sample 2

Average

Restriction

1

EC

dS/m

1.289

1.405

1.347

Low to moderate

TDS

mg/l

664

749

706.5

Low to moderate

2

SAR

0.88

0.97

0.93

No limitation

3

Na (surface irrigation)

SAR

0.88

0.97

0.93

No limitation

Na (sprinkler irrigation)

meq/l

3.09

2.74

2.92

No limitation

Cl (surface irrigation)

meq/l

22.3

24.8

23.55

Severe

Cl (sprinkler irrigation)

meq/l

Severe

4

N–NO3

mg/l

2.4

2.48

2.44

Severe

HCO3

mg/l

366

348

357

Severe

pH

7.69

7.77

7.73

No limitation

Conclusion

Suitable for irrigation except sensitive crops to Cl

Soil texture is moderately fine (20–30 % clay) and annually precipitation is 650 mm in Bandargaz region. Based on Table 7, Manual of Indian Council of Agricultural Research (Minhas and Gupta 1992) indicated that 2.5, 4.5 and 8 dS/m water salinity can be used for irrigation of sensitive, semi-moderate and moderate crops, respectively. Then, Bandargaz-treated wastewater is suitable for total crop irrigation.
Table 7

Manual of Indian Council of Agricultural Research (1992)

Soil texture (clay %)

Maximum level of water salinity (dS/m)

Sensitive crops

Annually rain (mm)

Semi-tolerant crops

Annually rain (mm)

Tolerant crops

Annually rain (mm)

<350

350–550

550–750

<350

350–550

550–750

<350

350–550

550–750

Fine (more than 30)

1

1

1.5

1.5

2

3

2

3

4.5

Moderately Fine (20–30)

1.5

2

2.5

2

3

4.5

4

6

8

Moderately Coarse (10–20)

2

2.5

3

4

6

8

6

8

10

Coarse (less than 10)

3

3

3

6

7.5

9

8

10

12.5

Classification of Bandargaz-treated wastewater based on Iranian guide for Water Quality Classification (IRNCID 2002) indicated that water is low saline and its usage is possible for total crop irrigation. Also, based on similar classification presented by IRNCID (2002), Bandargaz-treated wastewater can be used in light- and medium-textured soils without limitations and provided with leaching and drainage in clay soils.

The results showed that based on handbook No. 535 Iranian Ministry of Energy (2010), almost all indices except the chlorine were located in the range of use of treated wastewater for irrigation (Table 8). However, effluent discharge into receiving surface water is not permitted due to high levels of chlorine, calcium, ammonium, phosphorus, BOD, COD and TDS. Comparing average values of BOD5 and COD of influent and effluent wastewater in July (Table 1) and their yearly averages (Table 2) with Iranian Ministry of Energy (2010) standard (Table 8) showed that raw wastewater (influent) was suitable neither irrigation nor discharging into resource receiving surface water. However, based on Tables 1 and 2, effluent wastewater was suitable for irrigation purposes and discharging into surface water receiving resources.
Table 8

Assessment of effluent-treated wastewater based on Iranian Ministry of Energy (2010) (✓ no have limitation, ✗ have limitation, – no limitation)

Parameter

Unit

Permissible limits

Sample

Conclusion

Discharge into surface receiving

Irrigation

1

2

Average

Discharge into surface receiving

Irrigation

Cl

mg/l

600

600

790

880

835

SO4

mg/l

400

500

10

20

15

Ca

mg/l

75

460

248

354

Mg

mg/l

100

100

21.9

41.8

31.85

NH4

mg/l

2.5

34.5

30

32.25

NO2

mg/l

10

0.4

0.36

0.38

NO3

mg/l

50

2.4

2.48

2.44

PO4

mg/l

6

10.5

7

8.75

BOD5

mg/l

30

100

33

55

44

COD

mg/l

60

200

60

100

80

TSS

mg/l

40

100

28.4

29.6

29

pH

6.5–8.5

6.0–8.5

7.69

7.77

7.73

Turbidity

NTU

50

50

26

34

30

Fecal coliform

Count in 100 mL

400

400

>1100

150

Incomputable

Total coliform

Count in 100 mL

1000

1000

>1100

210

Incomputable

Myers et al. (1999) presented Australian guideline for sustainable effluent-irrigated plantations. This standard and results of Bandargaz-treated wastewater assessment are given in Table 9. The results showed that almost all indices except the chlorine were located in the range of use of treated wastewater for irrigation. Based on the average value of BOD5 of influent and effluent wastewater in July (Table 1) and its yearly average (Table 2), raw (influent) and treated (effluent), wastewater had medium and low risk, respectively, for sustainable irrigated plantations (Table 9).
Table 9

Australian guideline and the results of Bandargaz-treated wastewater assessment

Parameter

Unit

Risk

Sample

Conclusion

Low

Medium

High

1

2

Average

BOD5

mg/l

<40

40–1000

>1000

33

55

44

Low–medium

Total N

mg/l

<30

30–100

>100

34.5

30

32.25

Low

Total P

mg/l

<10

10–20

>20

10.5

7

8.75

Low

CaCO3

mg/l

<200

200–500

>500

600

580

590

Medium–high

TDS

mg/l

<500

500–2000

>2000

664

749

706.5

Medium

SAR

mg/l

<3

3–9

>9

0.88

0.97

0.93

Low

Cl

mg/l

<150

150–350

>350

790

880

835

High

B

mg/l

<0.5

0.5–3

>3

pH

6.5–8.5

7.77

7.77

7.77

No limit

Assessment of effect of wastewater on soil

Soil physical and chemical parameters are shown in Table 10. The results show that the soil salinity in wastewater-irrigated area is little more than fresh water irrigated land. Similar results were reported by Taghvaiian et al. (2008), Hoseinpoor et al. (2008) and Chen et al. (2013b). Maas and Hoffmann (1977) and Ayers and Westcot (1985) presented yield loss (%) per unit increase of soil salinity excessive from soil salinity threshold value (ECe), where yield decrease starts (ranging from 1.5 dS/m for sensitive to 10 dS/m for salt-tolerant crops). For rice, these values are 3 dS/m and 12 %. Comparing these values with Table 10 shows that application of wastewater did not lead to increase of soil salinity beyond rice salinity threshold.
Table 10

Soil physical and chemical parameters based on saturation extract

Parameter

Unit

Wastewater-irrigated soil

Fresh water irrigated soil

Before seeding

Mid growth season

Before seeding

Mid growth season

Field 1

Field 2

Field 1

Field 2

Saturation percent

%

62.8

57.7

66

65.1

61

58

ECe

dS/m

3.0

2.3

3.0

2.5

2.1

2.0

pH

7.7

7.8

7.6

7.5

7.36

7.8

Ca + Mg

meq/l

19.8

16.4

17.2

15.4

13.1

14.0

Na

meq/l

15.2

9.8

15.2

11.9

10.1

12.6

HCO3

meq/l

7.0

8.2

6.8

8.4

5.0

6.6

CO3

meq/l

0

0

0

0

0

0

SAR

(meq/l)0.5

4.8

3.4

5.2

4.3

3.9

4.8

RSC

meq/l

0

0

0

0

0

0

ESP

%

5.5

3.6

6.0

4.8

3.4

5.4

Organic carbon

%

1.26

1.02

0.98

1.09

1.01

0.90

Total N

%

0.12

0.13

0.11

0.11

0.10

0.14

Absorbable P

mg/l

18.4

11.1

18.9

39.3

11.6

13.7

Absorbable K

mg/l

80

80

100

120

65

70

Clay

%

22

22

22

20

19

21

Silt

%

54

48

54

60

55

61

Sand

%

24

30

24

20

26

18

Soil texture

Silty loam

Soil infiltration

mm/h

18.5

19.2

16.3

15.1

17.2

17.4

Richards (1954) divided soils into five categories on the basis of effects of soil salinity on crop yield. On the basis of Richards method (1954), soil salinity is relatively low and it has not limitations for different crops. However, yield of salt sensitive crops may be reduced in this condition.

Shainberg and Oster (1978) presented crops sensitivity to sodium hazard based on soil ESP. Crops were divided into five categories including very sensitive, sensitive, semi-tolerant, tolerant and very tolerant. Soil chemical parameters (Table 10) showed that in comparison with fresh water, the mid-term use of wastewater results in little increase of ESP but it did not cause the restrictions on soil even for sensitive crops. Chen et al. (2015b) observed a slight soil alkalization under reclaimed water irrigation that was in accordance with these findings.

Based on the criteria of Rhodes et al. (1992), the soil salinity in wastewater-irrigated area creates restrictions only for sensitive crops and there are no limitations for other plants.

Comparison of soil properties with Iranian guide for the irrigated land classification (2002) indicated that soil has any restriction in the aspect of salinity and sodium hazard.

Table 10 shows that in comparison with fresh water, the mid-term use of wastewater caused the increasing total N, absorbable P and absorbable K of soil. It was due to the high concentration of those elements in treated wastewater that were 35.07, 8.75 and 72 ppm, respectively (Table 5). Significant increase of N, P and K in soil irrigated by wastewater was reported by Meli et al. (2002), Salehi et al. (2008) and Singh and Agrawal (2012). Chen et al. (2015b) showed that soil nutrient conditions were ameliorated by reclaimed water irrigation, as indicated by the increase of soil organic matter content, total nitrogen and available phosphorus.

The results showed that the wastewater application did not reduce soil infiltration and even in some cases, it increased soil infiltration rate as well. Slight increase of soil infiltration rate was reported by Taghvaiian et al. (2008) according to this result. It happened because of increased soil organic carbon and Ca + Mg concentration.

Conclusion

Results showed that the treated wastewater is suitable for irrigation based on standards and criteria of United State Salinity Laboratory (Richards 1954; Wilcox 1955), Ayers and Westcot Guide (1985), Manual of Indian Council of Agricultural Research (1992), Australian guideline (1999), Iranian guide for Water Quality Classification (IRNCID 2002) and handbook No. 535 Iranian Ministry of Energy (2010). In comparison with fresh water, the mid-term use of wastewater did not cause the restrictions on soil in the aspect of salinity and sodium rate on the basis of Richards (1954), Shainberg and Oster (1978), Rhodes et al. (1992), and Iranian guide for the irrigated land classification (2002).

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Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Authors and Affiliations

  1. 1.Department of Water Engineering, Gorgan BranchIslamic Azad UniversityGorganIran

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