Survey on removal efficiency of linear alkylbenzene sulfonate in Yazd stabilization pond
Asghar Ebrahimi1, Mohammad Hassan Ehrampoosh1, Mohammad Reza samaei2, Ebrahim Shahsavani3, Elham Hosseini4, Hassan Hashemi2, Parvaneh Talebi1, Seyed Vahid Ghelmani5, Majid Dehghan1, Atefe Honardoost1
1 Department of Environmental Health Engineering, School of Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran
2 Department of Environmental Health Engineering, School of Health, Shiraz University of Medical Sciences, Shiraz, Iran
3 Department of Environmental Health Engineering, School of Health, Jahrom University of Medical Sciences, Jahrom, Iran
4 Department of Electrical Engineering, Azad University of Najaf Abad, Isfahan, Iran
5 Wastewater Treatment Plant, Yazd, Iran
|Date of Web Publication||08-Apr-2015|
Prof. Mohammad Hassan Ehrampoosh
Department of Environmental Health Engineering, School of Health, Shahid Sadoughi University of Medical Sciences, Yazd
Source of Support: None, Conflict of Interest: None
Aims: In this study, removal efficiency of linear alkylbenzene sulfonate (LAS) in Stabilization pond plant was investigated.
Materials and Methods: In this study, 64 samples were taken for 1-year in stabilization pond plant of Yazd city, central of Iran, in 2010. The samples were analyzed according to the standard methods. Methylene blue active substances were used to determine the amount of anionic surfactants.
Results: The most removal efficiency of anionic surfactants occurred in secondary facultative stabilization pond in summer and the least removal efficiency of anionic surfactant in anaerobic stabilization pond in the autumn was obtained.
Conclusion: According to the environmental standards for discharge of treated wastewater to the surface water, agricultural water usage and discharge to absorbent wells with P < 0.5 have significant difference values are more than standards.
Keywords: Facultative pond, linear alkyl benzene sulfonate, stabilization pond, Yazd city
|How to cite this article:|
Ebrahimi A, Ehrampoosh MH, samaei MR, Shahsavani E, Hosseini E, Hashemi H, Talebi P, Ghelmani SV, Dehghan M, Honardoost A. Survey on removal efficiency of linear alkylbenzene sulfonate in Yazd stabilization pond. Int J Env Health Eng 2015;4:10
|How to cite this URL:|
Ebrahimi A, Ehrampoosh MH, samaei MR, Shahsavani E, Hosseini E, Hashemi H, Talebi P, Ghelmani SV, Dehghan M, Honardoost A. Survey on removal efficiency of linear alkylbenzene sulfonate in Yazd stabilization pond. Int J Env Health Eng [serial online] 2015 [cited 2019 Dec 11];4:10. Available from: http://www.ijehe.org/text.asp?2015/4/1/10/153995
| Introduction|| |
Wastewater stabilization pond is a simple, cost-effective and easy maintenance for urban wastewater treatment, even in tropical areas. It generally consists of a series of anaerobic, facultative and maturation ponds. In this system, the pollutants are removed from wastewater streams through sedimentation or conversion in biological and chemical processes.  Schematic of Yazd wastewater stabilization pond is shown in [Figure 1] and its specifications are presented in [Table 1]. Wastewater is one of the main sources of water pollution in developing countries. Detergents used in household and industrial has enhanced these compounds in urban and industrial wastewater.  surfactants have a high solubility in water. That can cause foam formation in wastewater treatment plants and receive water. , Biodegradation capabilities of surfactants are relatively low, and they are often highly toxic. Major concern surfactants are lower the surface tension of water, also reduce the amount of oxygen transfer. , These compounds can cause taste and odor changes. Growth of aquatic plants and algae consume the oxygen dissolved in the water and leads to fish death. Degradation and destruction of ecosystems, eutrophication phenomenon due to phosphates increase, lack of appropriate degradation and causing physiological reactions in consumers of contaminated water are other negative effects of surfactants. Detergents in destroying viruses and bacteria affect the metabolism of stopping. Detergents cause microorganisms' membrane rupture and enzyme loss; also, they slow and disrupt enzymes activity affecting the bacteria respiration.  Linear alkylbenzene sulfonate (LAS) is the largest anionic surfactant group, which can be decomposed about 90-97% by bacteria and its amount in domestic wastewater is 3-21 mg/L. LAS structural formula is shown in [Figure 2].  The data indicate very similar toxicity levels of LAS to fish, with LC 50 values range from about 3 to 6 mg/L. data on the toxicity for algae, with EC 50 value in a range from 29 to 170 mg/L. Several aspects of mammalian toxicity are evaluated. Acute testing provides information on gross effects, such as mortality, from exposure to high doses. The data indicate minimal to moderate toxicity, with LD 50 values ranging from 500 to 2000 mg/kg body weight.  Ebrahimi et al. studies showed that aeration tanks with fixed beds and conventional activated sludge system achieved LAS removal efficiencies of 96% and 94% for an influent LAS concentration of 5 mg/L. At LAS concentrations higher than 5 mg/L the conventional activated sludge system did not have the required efficiency and its effluent did not meet the environmental discharge standards. In contrast, aeration tanks with fixed bed achieved a removal efficiency of 97% at higher concentrations (15 and 20 mg/L) and were capable of reducing the amount of effluent LAS concentration. 
Environmental Protection Agency, in 1989 recommended maximum secondary concentration of foaming agents to be 0.5 mg/L and in 1984 WHO indicated that no foaming agents should exist in raw water. The maximum amount of surfactant in drinking water is mentioned 0.2 mg/L. LAS over other detergents are manufactured, approximately 18% of all surfactants. In 1996, The Institute of Standards and Industrial Research of Iran determined the maximum permissible detergents in drinking water to be 0.2 mg/L. ,, The objective of this study determined removal efficiency of LAS in Yazd stabilization pond.
| Materials and Methods|| |
The scientific study was experimentally and aimed community is incoming wastewater to stabilization pond in Yazd city. Composite sampling was done. Samples were taken during four consecutive seasons. Sampling locations included:
- Treatment plant input,
- Anaerobic output,
- Primary facultative output, and
- secondary facultative output.
Parameters of pH, dissolved oxygen (DO), electrical conductivity (EC), and temperature were measured at the site and then samples were transported to the laboratory of Department of Health in University of Medical Sciences of Yazd adjacent to ice container. Methylene blue active substances were used to determine the amount of anionic surfactants by spectrophotometer in 605 nm wavelength. All sampling and testing conditions conducted based on guidelines in the standard methods book.  A t-test statistical test was conducted to compare the results with standard values using SPSS software version 11.5.
| Results|| |
Average results of tests on 1-year period of 16 samples from each pond are presented in [Table 2]. These data suggest that, ambient temperature was in the range of 20-26°C and DO concentration at the plant input and anaerobic output was zero and its value increased at primary facultative output to 4.8 mg/L and at secondary facultative output to 6.52 mg/L. EC increased in effluent compared to input wastewater, and its value was equal to 2396 μs/cm and the pH parameter was equal to 8-8.5. The annual average of LAS concentration at the plant input was 8.21 mg/L and reached 3.61 mg/L at secondary facultative pond output. Concentration fluctuations of surfactant at different sampling locations at four consecutive seasons are shown in [Figure 3]. The highest concentration of anionic surfactants is dedicated to winter and lowest in the mentioned areas except the secondary facultative output to autumn. The maximum concentration of anionic surfactant at input equals to 10.85 mg/L in winter and at output equals to 3.02 mg/L in summer. Anionic surfactant concentration changes in different sampling locations show an early uptrend in its value and then a downtrend. As observed in [Figure 4], in all seasons, the surfactant concentration increased in anaerobic pond output and then reduced in the output of primary and secondary facultative ponds. Average increase percentage in anaerobic pond output was 9.7% the maximum of which was 14 % in winter, and the minimum was 5.2% in autumn. As shown in [Table 3], the anionic surfactant removal efficiency in spring, summer, autumn, and winter, was 60.9, 67, 27, and 35.5, respectively. Maximum anionic surfactants removal efficiency in these ponds was in the summer and the minimum in autumn. Annual average removal percentage equals to 50%. Comparison of LAS average in different seasons with the environmental standards of Iran is presented in [Figure 4]. The results show that the output amount of anionic surfactants, in spring, summer and autumn are about twice the amount authorized for discharge to surface water and about 6 times the amount authorized for agricultural use and discharge into adsorbent wells. In the winter, the output value reached more than double that of other seasons and with the same ratio it exceeded the standard level. The results of the statistical tests of the present study show that there are significant differences between the average anionic surfactant in the effluent from stabilization ponds in Yazd and environmental standards for discharge to surface water (1.5 mg/L), agricultural irrigation (0.5 mg/L) and discharge into adsorbent wells (0.5 mg/L) (P < 0.05).
|Figure 3: Seasonal variation of anionic surfactants in different sampling locations|
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|Figure 4: Comparison of linear alkyl benzene sulfonate in seasons with environmental standards of Iran|
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|Table 2: Average LAS, specifications and characteristics of wastewater samples during 1-year|
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|Table 3: Comparison of LAS average concentration at input wastewater and effluent and removal efficiency in different seasons in mg/L|
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| Discussion|| |
Linear alkyl benzene sulfonate concentrations at ponds input different in seasons. In the winter, it reaches its maximum and in autumn it is at minimum. Factors such as weather conditions changes, customs and traditions of the people, industrial wastewater discharges, LAS biodegradation in the transmission path to wastewater treatment plant, and wastewater flow fluctuations are the most important factors influencing concentration variations of wastewater entering stabilization ponds. The results show that the amount of anionic surfactant in all seasons in anaerobic ponds output is more than in wastewater input, and this increase in winter is higher than other seasons. As number of sunny days and temperature are important parameters affecting the removal efficiency in stabilization ponds, they can be stated as the reason for low efficiency in winter, on the other hand, the activity of microorganisms and decomposition and conversion of substances because of enzymes interference will lead to the production of organic and nonorganic acids and CO 2 that eventually will reduce the pH. pH reduction affects dissolving and release of LAS. , Results from Peng et al. study on phosphorus removal by stabilization ponds show that the pH of ponds' content is effective on the phosphorus amount so that in pH of 7-8, the highest rate of phosphorus removal occurs.  The results indicate that EC in effluent is enhanced because the wastewater entering the ponds spends a long time to leave them, and high evaporation rate in the city of Yazd leads to water evaporation and salts retention, as a result, the EC increases. Comparison of DO and anionic surfactants in [Table 1] shows an inverse relation between the amount of anionic surfactants and DO in aerobic conditions in primary and secondary facultative ponds. Hence that the more anionic surfactants in the ponds, the less DO will be, because these substances can remain on water surface and prevent oxygen exchange between ponds and atmosphere, and the more surfactants are removed from ponds, the more amount of DO increase. Martin and Johannes studies showed that the surfactant can reduce aerate rate to <55% and oxygen transfer rate to <20%.  Ebrahimi et al. studies showed that when LAS increase 1 mg/L the concentration of chemical oxygen demand 2.5 mg/L is higher.  Comparing seasonal analysis of the results with national environmental standards shows that anionic surfactant concentration in stabilization Ponds' effluent is higher than environmental standards of Iran and it is recommended to take special considerations in reuse or discharge of the effluent. 
| Conclusion|| |
Surfactant concentration in the wastewater entering the treatment plant varies in different seasons. The concentration of LAS in anaerobic ponds system output increases compared to its input, and in winter this increase will be more than other seasons. The EC increases due to high evaporation in the system output compared with its input; moreover surfactant concentration and DO are inversely related.
| Acknowledgments|| |
The authors want to appreciate cooperation of Mr. Akrami and Salehi from Water and Sewage Company of Yazd, also would like to give special thanks to Ms. Talebi, Head of Chemistry Laboratory of Yazd Health Department.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3]