Print this page Email this page
Users Online: 800
Home About us Editorial board Search Browse articles Submit article Instructions Subscribe Contacts Login 

Previous article Browse articles Next article 
Int J Env Health Eng 2013,  2:24

Coliforms removal by an integrated activated sludge-maturation pond system

1 Department of Environmental Health Engineering, Faculty of Health, Kashan University of Medical Sciences, Kashan, Iran
2 Department of Environmental Health, Faculty of Health, Esfahan University of Medical Sciences, Isfahan, Iran

Date of Web Publication10-Jun-2013

Correspondence Address:
Mohammad Bagher Miranzadeh
Department of Environmental Health Engineering, Faculty of Health, Kashan University of Medical Sciences, Kashan
Login to access the Email id

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/2277-9183.113213

Rights and Permissions

Aims: This study assesses the removal of fecal indicators (i.e., total coliforms, fecal coliforms) in a full-scale activated sludge and maturation pond system with primary screening facility that is operating in center of Iran.
Materials and Methods: A total of 54 grab samples for microbiological test were collected from the inlet and outlet of activated sludge (AS) and maturation pond (MP) during the winter and summer 2010 (3 sample per month in 3 locations). Collected samples were sent to laboratory and were analyzed for total coliformbacteria (TCB) and fecal coliform bacteria (FCB) according to Standard Methods. Results: The results of this study show that the maximum TCB removal in AS (92.2%) and MP (99.2%) were occurred in summer. Also, for FCB, the highest removal rate (99.7%) was recorded during the summer. The mean winter TCB numbers for AS and MP effluents were 2.7 × 10 7 and 2.3 × 10 6 (MPN per 100 ml), respectively. However, the effluent still contained a significant number of coliforms, which was greater than the permissible limit for unrestricted irrigation as prescribed by Iranian and WHO guidelines.
Conclusion: Removal efficiencies of fecal indicator bacteria were maximum during summer and minimum during winter. Statistical analysis indicated that TCB and FCB removal in MP is significantly affected by ambient temperature, whereas there was weak correlation between ambient temperature and coliform removal in AS system.

Keywords: Activated sludge, coliform removal, maturation pond, wastewater treatment

How to cite this article:
Miranzadeh MB, Dehghani R, Bigdeli M, Tehrani AM, Heidari M. Coliforms removal by an integrated activated sludge-maturation pond system. Int J Env Health Eng 2013;2:24

How to cite this URL:
Miranzadeh MB, Dehghani R, Bigdeli M, Tehrani AM, Heidari M. Coliforms removal by an integrated activated sludge-maturation pond system. Int J Env Health Eng [serial online] 2013 [cited 2022 Jan 22];2:24. Available from:

  Introduction Top

The most appropriate wastewater treatment is that which will produce an effluent, meeting the recommended microbiological quality guidelines both at low cost and with minimal operational and maintenance requirements. Different system are used worldwide for wastewater treatment such as activated sludge, trickling filter, and waste stabilization pond or a combination of them in series. [1],[2] In Iran, because of water shortage, main usage of treated wastewater is for unrestricted irrigation. [3]

The potential presence of pathogens in treated effluent is assessed using indirect measures such as coliform bacteria, which is indicator of the safety of effluent. World health organization (WHO) has recognized total coliform bacteria (TCB) and fecal coliform bacteria (FCB) as the key fecal indicator. These indicators provide a total spectrum of waterborne disease. Total coliform indicate the presence of bacterial pathogens while FCB indicates the presence of bacterial pathogens as well as the presence of enteric viruses through vogue their relationship being with coliphages. [4],[5] Coliform removal efficiencies in WTP are utilized as indicators of the ability of the process to affectively remove pathogenic viruses and bacteria. Thus, the effectiveness of wastewater treatment systems with respect to the elimination of microbial pollution is often measured by determining the numbers of TCB and FCB in effluent of WTP. [2],[5]

The process responsible for the reduction of coliform and pathogen population in WTP systems are known to be controlled by a combination of physical, chemical, and biological factors. [2],[6],[7],[8] Viruses may be adsorbed by soil, the treatment media and organic litter, or deactivated due to lack of an appropriate host. On the other hand, in natural wastewater treatment processes such as waste stabilization pond (WSP), the bacteria are mainly removed by sedimentation, high retention time, exposure to sunlight, alkaline condition, natural die-off, and predation by zooplankton. Efficiency analysis for WTP must take into account local climatological conditions, especially ambient temperature and sunlight. [2],[5],[9],[10],[11]

Worldwide studies on various wastewater treatment plants were revealed that activated sludge process can remove indicator microorganisms up to 99% and for WSP system in the case of proper design and operation, this values can reach up to 99.999%. Also, efficiency removal of fecal bacteria in natural wastewater treatment process were higher in warm seasons rather than in cold seasons. [8],[12],[13]

Kashan is a tropical city in center of Iran with an estimated population of over 200,000 residents and is located at 930 m above the sea level. In this city, the university of medical sciences has commissioned since 1986 and at now, has over 3000 students in the field of medicine and health. The water consumption in this university is supplied by a deep water well. A wastewater treatment plant (WTP) consisting of an activated sludge system (extended aeration) and a maturation pond is now in operation in series. The wastewater is mainly domestic, and mean daily flow rate is 300 cubic meter per day. Because of economical and technical problems, the chlorination system was the out of service, and instead a maturation pond with rock baffle was constructed in series to activated sludge system. Final effluent from this WTP is used for irrigation of lawn and a variety of trees in surrounding of university under on surface drip irrigation system. Hence, quality control of the treated effluent, particularly its microbiological quality, is of considerable concern because of public health and environment protection. [3]

The main objective of the current research was the evaluation of the TCB and FCB bacteria removal efficiency in a full-scale integrated activated sludge - maturation pond wastewater treatment system in Kashan university of medical sciences.

  Materials and Methods Top

The experimental work on the performance evaluation of Kashan university of medical sciences wastewater treatment plant (Kaums-WTP) for pathogen removal was based on the use of indicator organisms, specifically TCB and FCB bacteria.

Wastewater treatment plant

The Kashan university of medical sciences wastewater treatment plant comprises of lift station, bar screen, two aeration tank in parallel with surface aerator, secondary clarifier, chlorination system (out of service), and a maturation pond with rock baffle [Figure 1]. Details of each unit in the system are shown in [Table 1]. The system was designed to remove biochemical oxygen demand (BOD), total suspended solid (TSS), and pathogenic microorganisms. Disinfection is not applied on AS effluent. The effluent of Kaums-WTP systemis used for lawn and plants watering in areas surrounding the university. [Table 2] presents the minimum, maximum, and average of ambient temperature for the region during the studied period. As it is reported in [Table 2], the daily average of ambient temperature was about 19.8°C in the studied region.
Table 1: Minimum, maximum, and average of ambient temperature in Kashan city for the monitoring period

Click here to view
Table 2: Dimensions and hydraulic retention time of each unit in kashans‑.WTP

Click here to view
Figure 1: Schematic of kashan university of medical sciences wastewater treatment plant

Click here to view

Wastewater sampling

Raw and treated wastewater samples were simultaneously collected three times per month during the winter and summer 2010 at three different locations including influent (raw sewage), outlet of AS, and MP system. Grab sampling procedure was adopted for microbiological analysis as per the methods prescribed in standard methods. [14] Wastewater samples for microbiological test were collected from inlet and outlet units of treatment plants in non-reactive sterilized borosilicate glass bottle of 250 ml capacity. Sample collection dates were randomly chosen, and all collections were done between 08:00-10:00 am. The collected samples were brought in an insulated container during transport. The samples were analyzed in water and wastewater laboratory, faculty of health, Kashan university of medical sciences on the same day of sample collection.

Sample analysis

The number of total and fecal coliforms was determined using the most probable number (MPN) method. Total coliform and fecal coliform were enumerated by multiple tube fermentation technique as described in standard methods for the examination of water and wastewater, by using laurel tryptose broth incubated at 35°C (24-48 h) for TCB and medium incubated at 44°C (24-48 h) for FCB. [14] Statistical tables were used to interpret the results, which were expressed as number of organism in 100 ml of the sample.

  Results Top

The monthly variation in TCB and FCB bacteria for Kaums-WTP in the winter and summer of 2010 are shown in [Table 3] and [Table 4]. The number of TCB and FCB in raw sewage ranged between 8.3 × 10 7 to 2.1 × 10 8 and 9.1 × 10 6 to 9.1 × 10 7 during winter, while TCB and FCB varied from 8.6 × 10 7 to 1.9 × 10 8 and 1.8 × 10 7 to 4.1 × 10 7 (MPN per 100 ml) in summer, respectively. From [Table 3], the mean winter TCB numbers for AS and MP effluents were 2.7 × 10 7 and 2.3 × 10 6 , respectively, and from [Table 4], the corresponding summer values were 1.03 × 10 7 and 6.67 × 10 4 MPN/100 ml, respectively. The mean FCB numbers for AS and MP effluent in winter were 4.5 × 10 6 and 3.04 × 10 5 , and in summer were 2.17 × 10 6 and 5.6 × 10 3 MPN/100 ml, respectively.
Table 3: Total and fecal coliform number for Kaums‑.WTP during winter 2010

Click here to view
Table 4: Total and fecal coliform number for Kaums‑.WTP during summer 2010

Click here to view

Total and fecal coliforms monthly average removal efficiencies for Kaums-WTP are shown in [Figure 2] and [Figure 3]. As shown in [Figure 2] for winter, TCB and FCB removal rates were 78.4% (February) to 81.2 (July) and 74.5% (February) to 83% (March) in AS system and for MP were 82.95% (March) to 94.7% (February) and 86.2% (March) to 97.4% (February) as respectively. Also, seasonally average removal of TCB and FCB in Kaums-WTP were shown in [Figure 4]. The overall average removal of TCB and FCB by AS system were found to be 86% and 94.2%, respectively. The corresponding values for MP system were 95.5% and 96.5%, respectively. The TCB and FCB removal in total system (AS-MP) were 99.16% and 99.86% during studied period.
Figure 2: Monthly average removal of TCB and FCB in AS system

Click here to view
Figure 3: Monthly average removal of TCB and FCB in MP system

Click here to view
Figure 4: Seasonally average removal of TCB and FCB in Kaums ‑WTP

Click here to view

  Discussion Top

The number of the two pathogen indicators in the raw sewage is quite different for the two season with an increase during the winter. Because of low water consumption in winter, the numbers of TCB and FCB in raw sewage were greater in winter respect to in summer. [12],[13] Based on obtained results, we concluded that in AS system, a considerable number of microbes were left in the effluent and could not be removed by AS process; therefore, an additional treatment step is required to remove microbes more effectively. The results show that, the minimum number of the indicator bacteria were recorded in the warmer month, which might be attributed the rapid die-off with increasing of solar radiation and higher temperature. Exposure to sunlight (UV radiation) is the main mechanism of bacterial die-off. Also, high pH values produced during algal photosynthesis is an important parameter for bacterial death in stabilization pond. [9],[12],[15]

The maximum TCB removal in AS system (92.2%) and MP (99.2%) were occurred during summer 2010. For FCB, the highest removal rates were recorded during summer 2010 (92.9% in AS system and 99.7% in MP). The results are in coherence with the findings of earlier studies that stated 90-98% reduction of bacteria in AS process. [6],[12],[16],[17] Study by Barjenbrach and Erler showed that removal rate of TCB and FCB reaching to 99.99% in maturation pond is not in agreement with our study finding. This difference is due to lower retention time and higher depth (1.5 m) in MP in Kaums-WTP. Other research finding shows that shallow maturation ponds (0.4 m) were more efficient as microbiological disinfection than deeper ones. Coliform die-off in pond decreases with an increase in pond depth. [17],[18],[19],[20],[21]

Coliform removal efficiencies in wastewater treatment plants are utilized as indicators of the ability of the process to effectively remove pathogenic viruses and bacteria. [7],[11],[22] Based on the data reported in [Table 3] and [Table 4], it was observed that the treated effluent in Kaums-WTP still contained significant numbers of TCB (6.1 × 10 4 - 2.07 × 10 6 MPN/100 ml) and FCB (5.2 × 10 3 -2.3 × 10 5 MPN/100 ml) during the period studied. These numbers are greater than the permissible limit specified by Iranian (TCB ≤ 1000 and FCB ≤ 400 MPN/100 ml) and WHO (FCB ≤ 1000 MPN/100 ml) guidelines for unrestricted irrigation. This is probably due to insufficient hydraulic retention time in maturation pond because of an improper selection of design criteria. [4],[15],[20],[21],[23]

Based on another study, the overall removal of coliforms has been reported to be 90-95% and 90-98% in complete mix and extended aeration activated sludge system, respectively. Also, reported coliform removal in conventional activated sludge system was 98%. Earlier studies by kuivunen et al. on activated sludge plants have shown 90-99% enteric bacterial reductions, which is compatible nearly with our study findings. [5],[12],[22],[24]

Statistical analysis for Kaums-WTP shows no significant variation in coliform removal in AS system during all the months of studied period ( P = 0.08) because AS process performance is not strongly affected by ambient temperature. [12],[13] In contrast, in MP, a significant variation for coliform removal is found during winter and summer ( P = 0.02) because stabilization pond performance is directly affected by ambient temperature. This means that sunlight exposure is considered to be the most important causes of natural disinfection in the waste stabilization pond (WSP) and hence, indicator microorganisms die off is highly affected by ambient temperature. [10],[16],[19],[25] Thus, we investigated the effect of ambient temperature on inactivation of indicator bacteria as an exposure to sunlight, which is the main factor for disinfection in WSP system. [6],[16],[17],[20],[24] Among the climatological parameters, temperature and light intensity plays an important role in removal or inactivation of pathogens in WSP system. Based on findings of other study, it is observed that the fecal coliform mortality rate constantly increases with increasing pH and temperature. High level of dissolved oxygen (DO) due to algal photosynthesis (which is affected by ambient temperature) and high visible light are rapidly fatal to coliforms bacteria. [16],[17],[21] Pond depthis a critical limiting factor. In addition, the algae population and degree ofmixing are factors affecting penetration of solar radiation into the pond water. [8],[13],[21],[23],[25]

  Conclusions Top

Although overall reduction of TCB and FCB in Kaums-WTP has been found to be significant, still final treated effluent exceeds Iranian and WHO guidelines for unrestricted irrigation. Thus, hydraulic retention time in maturation pond must be increased to more than 10 days or another MP must be constructed in series with existing pond. Removal efficiency of TCB and FCB was maximum during summer (99.7%) and minimum during winter (79.95%); this emphasizes the role of climatological condition on wastewater treatment process. The effect of ambient temperature on removal efficiency of TCB and FCB on activated sludge system was not significant, but a significance correlation between coliform removal and ambient temperature was found in maturation pond. Coliforms removal by an integrated activated sludge- maturation pond system.

  Acknowledgment Top

The authors thank manager of water and wastewater laboratory, faculty of health, Kashan University of Medical Science for technical assistances.

  References Top

1.Campos C, Guerrero A, Cardenas M. Removal of bacterial and viral faecal indicator organisms in a WSP in choconta, Colombia. Water Sci Technol 2002;45:61-6.  Back to cited text no. 1
2.Antunes S, Dionisio L, Silva, MC, SValente M, JBorrego J. Coliforms as indicator of wastewater treatment plants. Greece: Energy, Environment, Ecosystems and Sustainable Development; 2007.  Back to cited text no. 2
3.Miranzadeh MB. Removal of pathogenic organisms from the effluent of a activated sludge system using maturation pond. J Biol Sci 2005;5:230-2.  Back to cited text no. 3
4.WHO. Guidelines for the safe use of wastewater in agriculture 2 nd ed. Geneva: SwitzerlandWorld Health Organization;. 2005.  Back to cited text no. 4
5.Kazmi AA, Tyagi VK, Trivedi RC, Kumar A. Coliforms removal in full-scale activated sludge plants in India, J Environ Manage 2008;87:415-9.  Back to cited text no. 5
6.Macedo SL, Aravjo AL, Pearson HW. Thermo-tolerant coliform bacteria decay rates in a full scale WSP in northeast Brazil. Water Sci Technol 2011;63:1321-6.  Back to cited text no. 6
7.Mburu N, Thumbi GM, Mayabi AO. Removal of bacterial pathogens from domestic wastewater in a tropical subsurface horizontal flow constructed wetland. Proceedings of Taal 2007: The 12 th World Lake Conference, 2008: 1010-1015.  Back to cited text no. 7
8.Tyagi VK, Kazmi AA, Chopra AK. Removal of indicators and pathogens in a waste stabilizations pond system treating municipal wastewater in India. Water Enviro Res 2008;80:2111-7.  Back to cited text no. 8
9.Curtis TP, Mara D. The effect of sunlight on mechanism for the die-off of fecal coliform bacteria in waste stabilization ponds. Research monograph in tropical public health engineering; No.1, 1994;1:4-17.  Back to cited text no. 9
10.Katachote D, Dangtago K, Siriwong C. Treatment efficiency in wastewater treatment plant of Hat Hai municipality by quantitative removal of microbial indicators. Available from:   Back to cited text no. 10
11.Hany M, Yehia Z, Shawky Z, Sabae J. Microbial pollution of water in el-salam canal. Vol 11. Egypt: IDOSI Publications; 2011. p. 305-9.  Back to cited text no. 11
12.Tchobanoglous G, Burton F, Stensel H. Wastewater enginering and reuse. New Dehli: Metcalf and Eddy inc mc-Graw Hill; 2003. p. 555-730.  Back to cited text no. 12
13.Arceivala SJ. Wastewater treatment for pollution control. New Delhi: Mc Graw-Hill; 2004. p. 106-49.  Back to cited text no. 13
14.Clesceri LS, Greenberg AE, Eaton AD. Standard methods for the examination of water and wastewater. 21 th ed. Washington D.C, USA: APHA, AWWA, and WPCF; 2005.  Back to cited text no. 14
15.Mara D. Design manual for waste stabilization pond in india. Leeds, Egland: Lagoon Technology International Ltd; 1997.  Back to cited text no. 15
16.Tadesse L, Green FB, Puhakka JA. Seasonal and diurnal variations of temprature, pH and dissolved oxygen in advanced integrated wastewater pond system treating tannery effluent. Water Res 2004;38:645-54.  Back to cited text no. 16
17.Oragui J, Cawley L, Arridge H, Mara D, Person H, Silva S. Pathogen removal kinetics in a tropical experimental waste stabikization pond in relation to organic loading, retention time and pond geometry. Joao pessoa, paraiba, Brazil: 3 rd lAWQ international Conference on Stabilization Ponds Technology and Applications; 1995.  Back to cited text no. 17
18.Hathaway JM, Hunt WF, Jadlocki S. Indicator bacteria removal in storm-water best management practices in charlotte, north carolina. J Environ Eng (New York) 2009;10:1943-7870.  Back to cited text no. 18
19.Racault Y, Boutin C. Waste stabilization ponds in France: State of the art and recent trends. Water Sci Technol 2005;51:1-9.  Back to cited text no. 19
20.Barjenbrach M, Erler C. A performance review of small German WSPs identifying improvement options. Water Sci Technol 2005;51:43-9.  Back to cited text no. 20
21.Sinton LW, Hall CH, Lynch PA, Davies-Colley RJ. Sunlight inactivation of fecal indicator bacteria and bacteriophages from waste stabilization pond effluent in fresh and saline waters. Appl Environ Microbiol 2002;65:1122-31.  Back to cited text no. 21
22.Oakey SM, Pocasangre A, Flores M, Monge J, Estrada M. Waste stabilization pond use in Central America: The experiences of El Salvador, Guatemala, Honduras and Nicaragua. Water Sci Technol 2000;42:51-8.  Back to cited text no. 22
23.Alcalde L, Oron G, Gillerman L, Salgot M, Manor Y. Removal of fecal coliforms, somatic coliphages and F- Specific bacteriophages in a stabilization pond and reservoir system in arid regions. Water Sci Technol 2003;3:177-84.  Back to cited text no. 23
24.Campos JR, Reali MAP, Rossetto R, Sampaio J. A wastewater treatment treatment plant composed of UASB reactor, activated sludge with DAF and UV disinfection, inseries. Water Pract Technol 2009;4:1-8.  Back to cited text no. 24
25.Suh CW, Lee JW, Hong YS, Shin HS. Sequential modeling of fecal coliform removals in a full-scale activated-sludge wastewater treatment plant using an evolutionary process model induction system. Water Res 2009;43:137-47.  Back to cited text no. 25


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1], [Table 2], [Table 3], [Table 4]

This article has been cited by
1 Coliforms removal efficiency of Wupa wastewater treatment plant, Abuja, Nigeria
Samson Balogun, T.C. Ogwueleka
Energy Nexus. 2021; 4: 100024
[Pubmed] | [DOI]
2 Predicting the concentration of total coliforms in treated rural domestic wastewater by multi-soil-layering (MSL) technology using artificial neural networks
Sofyan Sbahi,Naaila Ouazzani,Lahbib Latrach,Abdessamed Hejjaj,Laila Mandi
Ecotoxicology and Environmental Safety. 2020; 204: 111118
[Pubmed] | [DOI]
3 A global multinational survey of cefotaxime-resistant coliforms in urban wastewater treatment plants
Roberto B.M. Marano, Telma Fernandes, Célia M. Manaia, Olga Nunes, Donald Morrison, Thomas U. Berendonk, Norbert Kreuzinger, Tanel Tenson, Gianluca Corno, Despo Fatta-Kassinos, Christophe Merlin, Edward Topp, Edouard Jurkevitch, Leonie Henn, Andrew Scott, Stefanie Heß, Katarzyna Slipko, Mailis Laht, Veljo Kisand, Andrea Di Cesare, Popi Karaolia, Stella G. Michael, Alice L. Petre, Roberto Rosal, Amy Pruden, Virginia Riquelme, Ana Agüera, Belen Esteban, Aneta Luczkiewicz, Agnieszka Kalinowska, Anne Leonard, William H. Gaze, Anthony A. Adegoke, Thor A. Stenstrom, Alfieri Pollice, Carlo Salerno, Carsten U. Schwermer, Pawel Krzeminski, Hélène Guilloteau, Erica Donner, Barbara Drigo, Giovanni Libralato, Marco Guida, Helmut Bürgmann, Karin Beck, Hemda Garelick, Marta Tacão, Isabel Henriques, Isabel Martínez-Alcalá, Jose M. Guillén-Navarro, Magdalena Popowska, Marta Piotrowska, Marcos Quintela-Baluja, Joshua T. Bunce, Maria I. Polo-López, Samira Nahim–Granados, Marie-Noëlle Pons, Milena Milako
Environment International. 2020; 144: 106035
[Pubmed] | [DOI]
4 Appraisal of Suspended Growth Process for Treatment of Mixture of Simulated Petroleum, Textile, Domestic, Agriculture and Pharmaceutical Wastewater
Precious N. Egbuikwem,Iffat Naz,Devendra P. Saroj
Environmental Technology. 2019; : 1
[Pubmed] | [DOI]
5 Prevalence of aquatic entomofauna, the predators of mosquitoes, in the Zayandeh River of Central Iran
Shayeghi Mansoreh,Doosti Soghra,Bazrafkan Sara,Hosseini-Vasoukolaei Nasibeh,Vatandoost Hassan,Akhavan Amir Ahmad,Vatandoost Sajad,Arandian Mohamd Hossein
Asian Pacific Journal of Tropical Disease. 2014; 4: S240
[Pubmed] | [DOI]


Previous article  Next article
Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

  In this article
Materials and Me...
Article Figures
Article Tables

 Article Access Statistics
    PDF Downloaded354    
    Comments [Add]    
    Cited by others 5    

Recommend this journal