TROPICAL CONSTRUCTED WETLANDS FOR EFFLUENT TREATMENT OF MUNICIPAL UASB
REACTORS
By
NADEEM KHALIL Applied Mechanics Department
Submitted
in fulfillment of the requirements of the degree of Doctor of Philosophy
to the
INDIAN INSTITUTE OF TECHNOLOGY DELHI New Delhi India
July 2009
Y#i
62_8.54
KRA -T
Dedicated to any parents & family
Kunwer Khalil Ahmad Khan, Zeba Khalil (Parents) Mubashra, Fadila, Firaas and Omer
CERTIFICATE
This is to certify that the thesis entitled "Tropical Constructed Wetlands for Effluent Treatment of Municipal UASB Reactors" submitted by Nadeem Khalil to the Indian Institute of Technology Delhi, for the award of the Degree of Doctor of Philosophy, is a record of bonafide research work carried out by him under our supervision. The thesis work, in our opinion, has reached the standards fulfilling the requirements for the degree of Doctor of Philosophy.
This is further certified that the research report and results presented in this thesis have not been submitted in part or in full to any other university or institute for the award of any degree or diploma.
Supervisors:
- •
Dr. Atul Kumar Mittal Professor
Department of Civil Engineering Indian Institute of Technology Delhi New Delhi — 110016
India
Dr. Ashok Kumar Raghav Associate Professor
Department of Applied Mechanics Indian Institute of Technology Delhi New Delhi — 110016
India
Place: New Delhi
ACKNOWLEDGEMENTS
I would like to acknowledge and express my deepest gratitude to the following:
Professor Ashok Kumar Raghav and Professor Atul Kumar Mittal (my supervisors) for their guidance, support, freedom for ideas and confidence in me. They have been my true mentors all this while.
Aligarh Muslim University (AMU) Aligarh India for sponsoring and permit me to pursue the research under their faculty improvement programme.
PHED, Haryana (Public Health Engineering Department) for their permission to install my experimental system and using some of their utilities within the premises of 20 MLD sewage treatment plant at Faridabad, Haryana. Special thanks to Mr. A K Gupta, Chief Engineer, PHED Haryana.
AICTE (All India Council for Technical Education, New Delhi) for the award of National Doctoral Fellowship which supported this research.
Professor P K Sen, former Head of the Department (Applied Mechanics, IIT Delhi) for his prompt actions in providing grant for experimental set-up and other important aspects.
Professor Y Nath and Professor Suhail Ahmad, Applied Mechanics Department, ITT Delhi for their continuous motivation and encouragement. I would also like to specially acknowledge the recommendations of Prof. Y Nath, presently Head of the Applied Mechanics Department for my two weeks visit to Japan under JENESYS programme of the Government of Japan in December 2008.
Professor Wazahat Husain (Retired), Department of Botany AMU for his advise on macrophytes.
Sanjay, Maitri, Arun, Vijay and other lab staff for their help during sampling and analysis.
Saba, Saima (sisters), Arza (niece), Ahmad (nephew), Asim and Faisal (brothers) and Azeem Akbar and Rao Ghannam (brothers-in-law) for their continuous encouragement.
Saad, Sabeel, Arshi, Khalil (friends), Zia, Najam, Zaheer, (research colleagues) for their continuous motivation.
Mubashra (my wife) for her patience, understanding, trust, responsibility and caring children during my long absence from the home for this work.
My mother Zeba Khalil and father Kunwer Khalil Ahmad Khan for their blessings, care, concern and everlasting emotional courage.
(Nadeem Khalil)
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ACKNOWLEDGEMENTS
I would like to acknowledge and express my deepest gratitude to the following:
Professor Ashok Kumar Raghav and Professor Atul Kumar Mittal (my supervisors) for their guidance, support, freedom for ideas and confidence in me. They have been my true mentors all this while.
Aligarh Muslim University (AMU) Aligarh India for sponsoring and permit me to pursue the research under their faculty improvement programme.
PHED, Haryana (Public Health Engineering Department) for their permission to install my experimental system and using some of their utilities within the premises of 20 MLD sewage treatment plant at Faridabad, Haryana. Special thanks to Mr. A K Gupta, Chief Engineer, PHED Haryana.
AICTE (All India Council for Technical Education, New Delhi) for the award of National Doctoral Fellowship which supported this research.
Professor P K Sen, former Head of the Department (Applied Mechanics, IIT Delhi) for his prompt actions in providing grant for experimental set-up and other important aspects.
Professor Y Nath and Professor Suhail Ahmad, Applied Mechanics Department, ITT Delhi for their continuous motivation and encouragement. I would also like to specially acknowledge the recommendations of Prof. Y Nath, presently Head of the Applied Mechanics Department for my two weeks visit to Japan under JENESYS programme of the Government of Japan in December 2008.
Professor Wazahat Husain (Retired), Department of Botany AMU for his advise on macrophytes.
Sanjay, Maitri, Arun, Vijay and other lab staff for their help during sampling and analysis.
Saba, Saima (sisters), Arza (niece), Ahmad (nephew), Asim and Faisal (brothers) and Azeem Akbar and Rao Ghannam (brothers-in-law) for their continuous encouragement.
Saad, Sabeel, Arshi, Khalil (friends), Zia, Najam, Zaheer, (research colleagues) for their continuous motivation.
Mubashra (my wife) for her patience, understanding, trust, responsibility and caring children during my long absence from the home for this work.
My mother Zeba Khalil and father Kunwer Khalil Ahmad Khan for their blessings, care, concern and everlasting emotional courage.
(Nadeem Khalil)
ii
ABSTRACT
This research was started with questions about how constructed wetlands (CWs) could be used to improve the effluent quality of UASB (upflow anaerobic sludge blanket) reactors treating municipal sewage. It is hypothesized that role of local macrophytes (like Typha latifolia, Canna flaccida, Sagittaria lancifolia, and Ipomea aquatica), innovations in filter media, understanding of wastewater characteristics particularly toxicity from sulfides present in UASB effluent, and hydraulics can help in improving the performance of the constructed wetlands to treat the UASB effluent.
Field set-up consisted of five identical independent CWs beds/cells at pilot-scale level, installed at the full-scale 20,000 m3/d capacity UASB sewage treatment plant.
Macrophytes were planted in four beds and one bed was used as control. The performance of wetlands units was monitored for about two years at different hydraulic retention times (RT) simultaneously. These beds were initially operated as free-water surface (FWS) at 4 days retention time and then as sub-surface flow (SSF) conditions at 2, 4, and 8 days RT.
Beds planted with canna, typha and ipomea showed considerable reduction in organic matters, solids, turbidity and substantially removed nitrogen and coliforms. Study also revealed that sagittaria could not withstand with anaerobic effluent. However, typha and canna showed no detrimental effect.
Retention time has significant role in the removal process. Beds when operated at 4 and 8 days retention time produced better removal efficiency as compared to 2 days.
Data was verified by using ANOVA and t-tests. Characteristics of the effluent from UASB reactors (feed) varied widely, which affected the quality of effluent from CWs.
Overall BOD removal was 42% (typha), 37% (ipomea), 48.6% (canna) and 26%
(control) at 4 days HRT under FWS flow conditions. under SSF flow conditions at 4 days HRT, the BOD removal efficiency increased to 53% (typha), 45% (ipomea), 60% (canna) and 21% (control). The study also revealed that when HRT was increased from 4 days to 8 days, efficiency increased by 5 - 10 % in different beds.
Removal of Kjeldahl nitrogen (TKN) and ammonical nitrogen (NH3-N) are not very encouraging. Removal of TKN and NH3 averaged 35% and 52% for typha, 32% and 35% for ipomea, 56% and 51% for canna, 26% and 25% for control respectively. It is observed that during initial stages, removal of TKN and NH3 was better, but after few months of operations, efficiency decreased significantly in all the beds except canna.
Fate of sulphates and its conversion in UASB reactors was also studied. There is clear reduction of sulfides concentration in CWs. UASB effluent showed presence of sulfide concentration varying between 23 to 33 mg.L1which was reduced to less than 15 mg.E 1. In case of Canna, it was even reduced to less than 5 mg.L-1.
Tracer studies revealed that hydraulic behavior of the beds tends towards plug flow conditions. It has been determined from the data that actual hydraulic retention time (empty bed HRT) is less than half of the theoretical retention time in all the planted beds. Hydraulic efficiency was 60% for planted beds and 80% in unplanted bed.
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A model has been developed to predict performance of CWs for BOD removal. This model incorporates residence time and a constant depending upon the type of vegetation. The model was validated for 62 data-set which showed good correlation with the experimental observations with the maximum deviation of 5%. This validation is in agreement with Willmott Index. The proposed model can be used for design of CWs.
Present work establishes use of constructed wetlands for the treatment of UASB effluent as an integrated sustainable approach for sewage treatment in India and in countries of tropical climates where land is cheap and easily available.
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TABLE OF CONTENTS
CERTIFICATE
ACKNOWLEDGEMENTS II
ABSTRACT III
TABLE OF CONTENTS V
LIST OF TABLES X
NOMENCLATURE XII
CHAPTER 1 Introduction
1.1 GENERAL 1
1.2 FOCUS OF THIS RESEARCH AND ITS PRACTICAL
SIGNIFICANCE 4
1.3 ORGANIZATION OF THE THESIS 5
CHAPTER 2
Literature Review 7
2.1 GENERAL 7
2.2 CONSTRUCTED WETLANDS 8
2.2.1. TYPES OF CONSTRUCTED WETLANDS 9 2.3 REMOVAL MECHANISMS AND TRANSFORMATION
PROCESSES 13
2.4 VEGETATION 16
2.4.1. ROLE OF VEGETATION 16
2.4.2. VEGETATION MANAGEMENT 17
2.5 DESIGN AND OPERATIONS 19
2.5.1. SIZING OF THE BEDS 20
2.5.2. ASPECT RATIO 22
2.5.3. BED CLOGGING 22
2.5.4. MEDIA TYPE 23
2.5.5. BED DEPTH 24
2.5.6. PLANTING DENSITY 25
2.6 POST TREATMENT OPTIONS FOR ANAEROBIC
EFFLUENTS 25
2.6.1. POLISHING PONDS 26
2.6.2. OVERLAND FLOW SYSTEM 27
2.6.3. ACTIVATED SLUDGE 28
2.6.4. TRICKLING FILTERS 29
2.6.5. SUBMERGED AERATED BIO-FILTER 30 2.6.6. ROTATING BIOLOGICAL CONTACT (RBC) 32 2.7 PERFORMANCE OF THE CWS FOR WATER QUALITY 33
2.7.1. GENERAL PERFORMANCE 33
2.7.2. PERFORMANCE FOR ANAEROBIC EFFLUENTS (UASB
REACTORS) 34
2.8 MATHEMATICAL MODELS OF SSF CWS 37
2.9 HYDRAULICS OF THE CONSTRUCTED WETLANDS 41 2.9.1. WATER MOVEMENT IN THE HF CONSTRUCTED
WETLANDS 41
2.9.2. HYDRAULIC TRACER STUDIES 43
2.9.2.1 TYPES OF HYDRAULIC TRACERS 43
2.9.2.2 TRACER ANALYSIS 45
2.9.2.2.1 RESIDENCE TIME DISTRIBUTION
(RTD) CURVE 45
2.9.2.2.2 DISPERSION MODEL 46
2.9.3. HYDRAULIC EFFICIENCY OF CONSTRUCTED WETLANDS 50 2.10 SUMMARY OF REVIEW AND KNOWLEDGE GAPS 51 CHAPTER 3
Research Need, Objectives and Scope 55 3.1 NEED AND JUSTIFICATION OF THIS RESEARCH 55
3.2 AIMS, OBJECTIVES AND HYPOTHESES 61
3.3 SCOPE OF THE STUDY 62
3.4 APPROACH TOWARDS THIS STUDY 63
CHAPTER 4
Materials and Methods 65
4.1 GENERAL 65
4.2 MATERIALS 65
4.2.1. STUDY SITE AND UASB EFFLUENT SOURCE 65 4.3 DESIGN AND LAYOUT OF THE PILOT UNITS 66
4.4 CHOICE OF VEGETATION 72
4.5 FILTER MEDIA SELECTION 72
4.6 METHODS 75
4.6.1. START-UP AND ESTABLISHMENT OF MACROPHYTES 75
4.6.2. SYSTEMS OPERATIONAL STRATEGY 76
4.6.3. SAMPLING AND MONITORING 78
4.6.4. DATA ANALYSIS 79
4.6.5. SET-UP AND ANALYSIS FOR TRACER STUDY 80
4.7 CWS MAINTENANCE AND MANAGEMENT 82
CHAPTER 5
Constructed Wetlands for UASB Effluent Treatment 83
5.1 GENERAL 83
5.2 RESULTS AND DISCUSSIONS 84
5.2.1. GROWTH AND RESPONSE OF MACROPHYTES WITH
UASB EFFLUENT 84
5.2.2. TREATMENT PERFORMANCE 88
5.2.2.1 CHARACTERISTICS OF UASB EFFLUENT 88
5.2.2.2 ORGANIC MATTER 92
5.2.2.2.1 BOD REMOVAL 92
5.2.2.2.2 COD REMOVAL 101
5.2.2.3 SOLIDS AND TURBIDITY REMOVAL 107 5.2.2.4 NITROGEN AND AMMONIA-N REMOVAL 113 5.2.2.5 FEACAL COLIFORMS REMOVAL 119
5.2.3. FATE OF SULFIDES 122
5.3 APPLICABILITY OF UASB CWS COMBINATION 124 CHAPTER 6
Hydraulic Tracer Study of the Constructed Wetlands 127
6.1 GENERAL 127
6.2 COMPUTATION FOR DETERMINING HYDRAULIC
PARAMETERS 127
6.3 RESULTS AND DISCUSSIONS 131
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CHAPTER 7
Modelling CWs Performance 7.1 GENERAL
7.2 THEORETICAL CONSIDERATIONS AND MODEL DEVELOPMENT
7.3 MODEL VALIDATION CHAPTER 8
Conclusions and Recommendations CHAPTER 9
Suggestions for Future Work
135 135 137 142
145
149
REFERENCES 151 ANNEXURES
Annexure-III
Annexure-IV
Annexure-V
Preparation of Reagents and Procedure for Wastewater Analysis Summary of effluent after Final Polishing Ponds (existing post- treatment) at 20 MLD Sewage Treatment Plant at Faridabad, India measured during the study (n=36)
Evaluation of Life Cycle Cost for 20 MLD Capacity Sewage Treatment Plant based on different Treatment Options for two conditions, Urban Centres and Medium Sized Towns in India Cost comparison in between the two post-treatment methods (after UASB Reactors)
Compost pit for harvested biomass at the study site Annexure —I
Annexure-II
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