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DEVELOPMENT AND OPTIMIZATION OF CONSTRUCTED MANGROVE WETLAND
SYSTEMS FOR TREATMENT OF MUNICIPAL WASTEWATER
WU YAN
MASTER OF PHILOSOPHY
CITY UNIVERSITY OF HONG KONG
JANUARY 2008
CITY UNIVERSITY OF HONG KONG
香港城市大学
Development and optimization of constructed
mangrove wetland systems for treatment of
municipal wastewater
开发并优化红树林人工湿地作为生活污水的处
理系统
Submitted to
Department of Biology and Chemistry 生物及化学系
In Partial Fulfillment of the Requirements for the Degree of Master of Philosophy
哲学硕士学位
by
Wu Yan 伍彦
January 2008 二零零八年一月
Abstract i
Development and optimization of constructed mangrove wetland
systems for treatment of municipal wastewater
Submitted by Wu Yan
For the Degree of Master of Philosophy at City University of Hong Kong
(January, 2008)
Abstract
The discharge of untreated or partially treated municipal wastewater deteriorates
coastal and marine ecosystems. Conventional wastewater treatment methods are often
too complicated and too expensive for developing countries and small communities in
rural areas of developed countries. The constructed wetland treatment system with
annual plants has been employed as an alternative treatment method but it needs
frequent harvesting. The aim of this MPhil research is to develop and optimize a
subsurface flow constructed mangrove wetland system as a secondary municipal
wastewater process. A series of greenhouse studies using constructed mangrove
microcosms without tidal flushing were conducted under different hydraulic retention
times (HRT), mangrove plant species, salinities and the introduction of an idle period.
The study also evaluates the comparability between artificial wastewater and real
primary-settled municipal wastewater collected from a sewage treatment work in Hong
Kong SAR in treatment performance and outcome for wastewater-borne pollutants.
The results demonstrate that constructed mangrove tanks planted with Kandelia
Abstract ii
candel had significantly higher treatment efficiency than the unplanted tanks. The
removal percentages of dissolved organic carbon (DOC), ammonia-nitrogen (N),
inorganic-N, total Kjeldahl N and ortho-phosphate in the planted systems were
70.43-76.38%, 76.16-91.83%, 47.89-63.37%, 75.15-79.06% and 86.65-91.83%,
respectively. Plant growth as well as tissue N and phosphorus (P) concentrations and
uptake were enhanced by the addition of wastewater. The mass balance showed that
active nitrification and denitrification processes occurred in the mangrove system, with
25-30% N lost to atmosphere, while P was mainly accumulated in sediment. The
removal efficiency under 10-day HRT was better than that of 5-day but more land area
is needed for longer the HRT. The introduction of an idle period significantly enhanced
removal percentages of DOC and N as microbial activities in the soil were stimulated
after the idle period. The denitrification potential at the end of the second treatment
period was approximately 50-fold higher than that at the end of the first treatment
period.
Although the planted systems had better treatment performance than the unplanted
ones, no significant difference in removal efficiency was found among the three
mangrove species, namely Aegiceras corniculatum, Acanthus ilicifolius and Bruguiera
gymnorrhiza during the four-month wastewater treatment. All planted systems
effectively removed pollutants with 90% of DOC, 99% of ammonia-N, 78% of
inorganic N removal, and > 97% of TKN and inorganic P removed under 5-day HRT.
Abstract iii
The total amounts of N and P accumulated in the tissues of A. ilicifolius were
comparable to that of A. corniculatum and B. gymnorrhiza. However, the fate of
wastewater-borne pollutants and their distribution in different components of the
constructed mangrove wetland varied among the three mangrove species, indicating that
the root structure and oxygen released from roots of each mangrove species might be
different, which then altered the nutrient and transformation in the soil. The treatment
performance of mangrove microcosms planted with A. corniculatum was affected by
wastewater salinity, with a poorer rate of removal of DOC and N under high salinities
(15 and 30ppt, parts per thousands). Saline wastewater reduced the denitrification
potential. However, growth of A. corniculatum and tissue nutrient uptake was the
highest at 15ppt.
The removal percentages of DOC and P were different between artificial and real
municipal wastewater under the same treatment condition, probably due to the absence
of microorganisms, ions (particularly Fe3+ and Ca2+), trace elements and different forms
of organic matter and P in artificial wastewater, as these are difficult to simulate.
However, no significant difference in N removal was found between artificial and real
wastewater. This suggested that if the formula for preparing artificial wastewater is
further improved, it is possible to extrapolate data from artificial wastewater to real
wastewater situations.
Abstract iv
All effluent leaving the planted mangrove systems was able to meet the effluent
discharge standards of Water Control Zones set by the Environmental Protection
Department of Hong Kong SAR. The present research demonstrates the feasibility of
using constructed mangrove wetlands, without tidal flushing, as the secondary treatment
process for municipal wastewater, even for those with high salinity.
Table of Contents vii
Table of Contents
Abstract i
Acknowledgment v
Table of Contents vii
List of Tables xvii
List of Figures xxviii
Abbreviations xxxvi
Chapter 1 Introduction 1
1.1 General Introduction 1
1.2 Aims and objectives 3
1.3 Research plan 4
Chapter 2 Literature review 6
2.1 Problem of wastewater pollution 6
2.1.1 Sources and types of wastewater 6
2.1.2 Municipal wastewater 7
2.1.2.1 Quantities of municipal wastewater 7
2.1.2.2 Pollutants in municipal wastewater 9
2.1.2.3. Shortage of water and needs for water reuse 9
2.1.3 Nutrients and eutrophication problems 11
2.1.4 Toxic pollutant 11
2.2 Conventional technologies for municipal wastewater treatment 12
2.2.1 Physical methods 12
Table of Contents viii
2.2.2 Chemical methods 12
2.2.3 Biological methods 13
2.2.4 Wetland for wastewater treatment 15
2.3. Definition and distribution of wetland 15
2.3.1 Natural wetland ecosystems 15
2.3.2 Constructed wetlands 17
2.3.3 Significance of using wetlands for wastewater treatment 17
2.3.3.1 Wetland structure and function related to wastewater treatment 18
2.3.3.2 Examples of constructed wetlands for municipal wastewater
treatment
21
2.4 Mechanisms involved in wastewater treatment in constructed wetlands 21
2.4.1 Cycling of basic elements ( C, N, and P) in wetlands 21
2.4.1.1 Carbon 21
2.4.1.2 Nitrogen 24
2.4.1.3 Phosphorus 26
2.4.2 Removal of organic matter in wetlands 26
2.4.3 Removal of nutrients in wetland 27
2.4.3.1 Nitrogen removal 27
2.4.3.2 Phosphorus removal 29
2.4.3.3 Removal of bacteria and pathogens 30
2.4.3.4 Removal of suspended solids 30
2.4.3.5 Removal of toxic pollutants 31
2.5 Factors affecting wetland treatment efficiency 32
2.5.1 Flow patterns 32
2.5.2 Hydraulic retention time 35
2.5.3 Plant species and soil types 35
2.5.4 Salinity 36
2.5.5 Other factors 37
Table of Contents ix
2.6 Mangrove wetland for wastewater treatment 40
2.6.1 General features of mangrove wetland 40
2.6.2 Advantages of using mangrove wetland for wastewater treatment 41
2.6.3 Previous studies on mangrove wetland-wastewater treatment system 42
2.7 Limitation of using wetland for municipal wastewater treatment 44
2.7.1 Effects of wastewater on soils in wetland 44
2.7.2 Effects of wastewater on vegetations in wetland 45
2.7.3 Other limitations 46
Chapter 3 Effects of retention time on removal of nutrients and dissolved
organic carbon in primary settled municipal wastewater
48
3.1 Introduction 48
3.2 Materials and methods 49
3.2.1 Set-up of mangrove tide tanks 49
3.2.2 Collection of wastewater and soil sample 52
3.2.2.1 Sampling methods 52
3.2.2.2 Storage and preservation methods 52
3.2.3 Sample analyses 53
3.2.3.1 Analysis of soil sample 53
3.2.3.1.1 Soil porosity 53
3.2.3.1.2 Total organic carbon content 54
3.2.3.1.3 Inorganic nitrogen (ammonia-nitrogen and nitrate-nitrogen) 54
3.2.3.1.4 Inorganic phosphorus 55
3.2.3.1.5 Total P and total Kjeldahl N 55
3.2.3.1.6 Dehydrogenase activity 56
3.2.3.1.7 Denitrification potential 57
3.2.4 Measurement of water sample 58
Table of Contents x
3.2.4.1 Dissolved organic carbon, inorganic nitrogen and phosphorus 58
3.2.4.2 Total phosphorus and total Kjeldahl nitrogen 58
3.2.5 Plant determination 59
3.2.5.1 Plant growth 59
3.2.5.2 Nutrient concentrations (total phosphorus and total nitrogen) 59
3.2.6 Mass balance of nitrogen and phosphorous in mangrove tide tank
system
60
3.2.7 Determination of flow rate 61
3.2.8 Statistical analyses 61
3.3 Results 62
3.3.1 Wastewater treatment efficiencies 62
3.3.1.1 Removal of dissolved organic carbon 62
3.3.1.2 Removal of ammonia 63
3.3.1.3 Removal of nitrate 63
3.3.1.4 Removal of inorganic nitrogen 68
3.3.1.5 Removal of total Kjeldahl nitrogen 68
3.3.1.6 Removal of inorganic phosphorus 71
3.3.1.7 Removal of total phosphorus 71
3.3.2 Growth of mangrove plants 74
3.3.2.1 Initial properties of mangrove plants 74
3.3.2.2 Plant growth during wastewater treatment 74
3.3.2.3 Nutrient status of mangrove plants after wastewater irrigation 75
3.3.3 Characteristics of soils 79
3.3.3.1 Background properties of Sai Keng soils 79
3.3.3.2 Nutrients in the soil after wastewater treatment 79
3.3.3.2.1 Nitrogen 79
3.3.3.2.2 Phosphorus 84
3.3.3.3 Total organic matter 84
Table of Contents xi
3.3.3.4 Dehydrogenase activity 86
3.3.3.5 Denitrification potential 86
3.3.4 Mass balance of nutrients in constructed mangrove wetland
treatment systems
88
3.4 Discussion 94
3.4.1 Mangrove wetlands as a secondary wastewater treatment system 94
3.4.2 Mechanism of wastewater treatment in constructed mangrove
wetland
98
3.4.2.1 Role of mangrove plants 98
3.4.2.2 Roles of soil and microorganisms 100
3.4.3 Effects of HRT on treatment efficiencies 102
3.5 Conclusions 102
Chapter 4 Effects of using artificial wastewater on removal of nutrients
and dissolved organic carbon (DOC) in constructed mangrove
wetlands
104
4.1 Introduction 104
4.2 Materials and Methods 105
4.2.1 Experimental design and analyses 105
4.2.2 Preparation of artificial wastewater 106
4.2.3 Statistical analyses 106
4.3 Results 107
4.3.1 Wastewater treatment efficiencies 107
4.3.1.1 Removal of dissolved organic matter 107
4.3.1.2 Removal of nitrogen 108
Table of Contents xii
4.3.1.3 Removal of inorganic phosphorus (ortho-P) 116
4.3.2 Growth of mangrove plants under artificial and real wastewater
treatment
116
4.3.2.1 Plant growth 116
4.3.2.2 Nutrient status of mangrove plants after wastewater irrigation 118
4.3.3 Comparison of soil characteristic between discharge of artificial and
real municipal wastewater
122
4.3.3.1 Soil nutrient concentrations 122
4.3.3.2 Microbial activities in mangrove soil after wastewater treatment 127
4.3.4 Mass balance of nutrients in systems treated with artificial and real
wastewater
130
4.4 Discussion 135
4.5 Conclusions 136
Chapter 5 Effects of idle period on removal of nutrients and dissolved
organic carbon (DOC) in municipal wastewater
138
5.1 Introduction 138
5.2 Materials and Methods 139
5.2.1 Experimental design and analyses 139
5.2.2 Statistical analyses 140
5.3 Results 140
5.3.1 Effects of idle period on wastewater treatment efficiencies 140
5.3.1.1 Removal of dissolved organic carbon 140
5.3.1.2 Removal of nitrogen 141
5.3.1.3 Removal of inorganic phosphorus 145
5.3.2 Effects of idle period on growth of mangrove plants 150
5.3.2.1 Initial properties of mangrove plants 150
Table of Contents xiii
5.3.2.2 Plant growth after wastewater treatment 150
5.3.2.3 Nutrient status of mangrove plants after wastewater treatment 158
5.3.3 Effects of idle period on mangrove soil properties 161
5.3.3.1 Background properties 161
5.3.3.2 Chemical properties of soils after wastewater treatment 161
5.3.3.3 Microbial activities in mangrove soil after wastewater treatment 166
5.3.4 Mass balance of nutrients in systems during the first and second
wastewater treatment periods
170
5.4 Discussion 175
5.5 Conclusions 178
Chapter 6 Effects of three different mangrove species on constructed
mangrove wetlands for the treatment of artificial municipal
sewage
180
6.1 Introduction 180
6.2 Materials and Methods 181
6.2.1 Experimental design and analyses 181
6.2.2 Statistical analyses 182
6.3 Results 183
6.3.1 Wastewater treatment efficiencies 183
6.3.1.1 Removal of DOC 183
6.3.1.2 Removal of nitrogen 184
6.3.1.3 Removal of phosphorus 187
6.3.2 Plant growth 189
6.3.2.1 Initial properties of mangrove plants 189
6.3.2.2 Plant growth 192
6.3.2.3 Nutrient content of the three mangrove species after wastewater 195
Table of Contents xiv
treatment
6.3.3. Effects of different mangrove species on retention of
wastewater-borne pollutants in mangrove soil
197
6.3.3.1 Soil nutrients and total organic matter content before and after
wastewater treatment
197
6.3.3.1.1 Nitrogen 197
6.3.3.1.2 Phosphorus 200
6.3.3.1.3 Total organic matter 200
6.3.3.2 Microbial activities before and after wastewater treatment 203
6.3.3.2.1 Denitrification potential 203
6.3.3.2.2 Dehydrogenase activity 203
6.3.4 Mass balance before and after wastewater treatment 205
6.4 Discussion 210
6.4.1 Comparison of treatment efficiencies among different plant species 210
6.4.2 Fate of pollutants in wetlands planted with different mangrove
plants
211
6.4.3 Selection of mangrove plants 214
6.5 Conclusions 215
Chapter 7 Effects of salinity on treatment efficiencies of nutrients and
DOC by constructed mangrove wetland systems
216
7.1 Introduction 216
7.2 Materials and methods 218
7.2.1 Set-up of mangrove tanks 218
7.2.2 Statistical analysis 218
7.3 Results 219
Table of Contents xv
7.3.1 Wastewater treatment efficiencies 219
7.3.1.1 Removal of dissolved organic matter 219
7.3.1.2 Removal of nitrogen 219
7.3.1.3 Removal of inorganic phosphorus 222
7.3.2 Plant growth 225
7.3.2.1 Initial properties of mangrove plants 225
7.3.2.2 Plant growth 225
7.3.2.3 Nutrient status of A. corniculatum before and after the
four-month wastewater discharge
230
7.3.3 Effects of wastewater spiked with different salinities on nutrient
content of mangrove soil
230
7.3.3.1 Nitrogen 230
7.3.3.2 Phosphorus 234
7.3.3.3 Total organic matter (TOM) 234
7.3.3.4 Microbial activities 237
7.3.3.4.1 Denitrification potential 237
7.3.3.4.2 Dehydrogenase activity 237
7.3.4 Mass balance of nitrogen and phosphorus before and after
wastewater treatment
239
7.3.4.1 Nitrogen 239
7.3.4.2 Phosphorus 239
7.4 Discussions 244
7.4.1 Feasibility of using constructed mangrove wetlands for treating
wastewater with high salinity
244
7.4.2 Effects of salinity on treatment efficiency of mangrove wetland
systems
245
7.4.2.1 Effect on microbial activities in mangrove soil 245
7.4.2.2 Effects of salinity on the growth of A. corniculatum 247
Table of Contents xvi
7.5 Conclusions 248
Chapter 8 General discussion
250
8.1 Feasibility of using constructed mangrove wetland in treating primary
settled municipal wastewater
250
8.2 Optimization of mangrove constructed wetland treatment systems 253
8.3 Fate of wastewater-borne pollutants in constructed wetland treatment
systems
256
8.4 Contributions to original knowledge 257
8.5 Limitations of the present study and future research 259
8.6 Conclusions 262
References 265
Conferences and Publications 319
List of Tables xvii
List of Tables
Table 2-1 Examples of sources of wastewater in different places
8
Table 2-2 Composition of municipal wastewater (Units in mg L-1
except for pH)
10
Table 2-3 The major roles of macrophytes in constructed wetland
treatment systems
20
Table 2-4 Examples of using constructed wetlands for municipal
wastewater treatment
22
Table 2-5 Effects of recirculation on removal of total nitrogen (TN)
and ammonia (NH4+-N)
39
Table 2-6 Previous studies on wastewater treatment efficiencies by
mangrove
43
Table 3-1 Experimental design to examine effects of hydraulic
retention time (HRT) and mangrove plants
50
Table 3-2 Preservation methods of water samples
53
Table 3-3 Effects of plant and hydraulic retention time on wastewater
removal efficiency (in % except nitrate) during the 6-month
treatment of primary settled municipal sewage
65
Table 3-4 Two-way ANCOVA results (F-value) showing effects of 65
List of Tables xviii
hydraulic retention time (HRT) and plants on the
concentration of DOC, NH3-N, NO3--N, inorganic-N,
inorganic-P, TKN and TP in effluent
Table 3-5 Growth and biomass of K. candel before and after
wastewater irrigation
76
Table 3-6 Nutrient status of K. candel before and after wastewater
irrigation
77
Table 3-7 Background properties of Sai Keng mangrove soil
80
Table 3-8 Variations of initial background nutrient concentrations in
soil from different treatments
80
Table 3-9 Changes of concentration of nutrients and TOM in soil after
wastewater treatment
83
Table 3-10 Two-way ANOVA results showing effects of hydraulic
retention time (HRT) and plant on the percentages of
changes of nitrogen elements (NH4+, NO3
-, Inorganic N and
TKN) to the initial concentration in soil in tanks after
6-month wastewater treatment
83
Table 3-11 Two-way ANOVA results showing effects of hydraulic
retention time (HRT) and plant on the percentages of
changes of phosphorus elements (PO43-, TP) to initial
concentration in soil in mangrove tanks after 6-month
84
List of Tables xix
wastewater treatment
Table 3-12 Two-way ANOVA results showing effects of hydraulic
retention time (HRT) and plant on the percentage of changes
of TOM to initial concentration, denitrification potential and
dehydrogenase activity in soil in mangrove tanks after the
6-month wastewater treatment
87
Table 3-13 Microbial activities (dehydrogenase activity and
denitrification potential) in mangrove soil at the end of
6-month wastewater treatment
88
Table 3-14 Amount of input nitrogen from wastewater, soil and plant
over the 6-month wastewater treatment
90
Table 3-15 Amount of output nitrogen from wastewater, soil and plant
over the 6-month wastewater treatment
90
Table 3-16 Mass balance of nitrogen (mg) and percentages of individual
part of nitrogen to total nitrogen (in bold) in wastewater, soil
and plant over the 6-month wastewater treatment
91
Table 3-17 Amount of input phosphorus from wastewater, soil and plant
over the 6-month wastewater treatment
92
Table 3-18 Amount of output phosphorus from wastewater, soil and
plant over the 6-month wastewater treatment
92
Table 3-19 Mass balance of phosphorus (mg) and percentages of 93
List of Tables xx
individual part of phosphorus to total phosphorus (in bold) in
wastewater, soil and plant over the 6-month wastewater
treatment
Table 3-20 Removal efficiencies of different constructed wetlands for
sewage treatment
96
Table 3-21 Percentages of effluents complied with discharge standards
at different water bodies in Hong Kong set by the
Government
97
Table 4-1 Experimental design to examine effects of using artificial
wastewater on treatment efficiency of mangrove wetland
with 5-day HRT
105
Table 4-2 Characteristics of the artificial wastewater simulating real
municipal wastewater
107
Table 4-3 Compositions of stock solution used for preparing artificial
wastewater
107
Table 4-4 Effects of wastewater types (real and artificial wastewater)
on removal efficiency (in % except nitrate) during the
6-month treatment
111
Table 4-5 Two-way ANCOVA results (F-value) on concentrations of
DOC, NH3-N, NO3--N, inorganic-N, ortho-P, and TKN in
effluent from microcosm with different types of wastewater,
111
List of Tables xxi
and with and without plants
Table 4-6 Growth and biomass of K. candel before and after
wastewater irrigation
120
Table 4-7 Nutrients status of K. candel before and after wastewater
irrigation
121
Table 4-8 Changes of soil nutrients concentration of nutrients and total
organic matter in soil after wastewater treatment
125
Table 4-9 Two-way ANOVA results showing effects of types of
wastewater and plant on the percentages of changes of
nitrogen elements (NH4+, NO3
-, Inorganic N and TKN) to the
initial concentration in soil in systems after the 6-month
wastewater treatment
125
Table 4-10 Two-way ANOVA results showing effects of types of
wastewater and plant on the percentages of changes of
phosphorus elements (PO43-, TP) to initial concentration in
soil in mangrove tanks after 6-month wastewater treatment
127
Table 4-11 Two-way ANOVA results showing effects of types of
wastewater and plant on the changes of total organic matter,
denitrification potential and dehydrogenase activity in soil in
mangrove tanks after 6-month wastewater treatment
129
Table 4-12 Microbial activities (dehydrogenase activity and 129
List of Tables xxii
denitrification potential) in mangrove soil at the end of the
6-month wastewater treatment
Table 4-13 Amount of input and output nitrogen from wastewater, soil
and plant over the 6-month wastewater treatment
131
Table 4-14 Mass balance of nitrogen (mg) and percentages of individual
part of nitrogen to total nitrogen (in bold) in wastewater, soil
and plant over the 6-month wastewater treatment
132
Table 4-15 Amount of input and output phosphorus from wastewater,
soil and plant over the 6-month wastewater treatment
133
Table 4-16 Mass balance of phosphorus (mg) and percentages of
individual part of phosphorus to total phosphorus (in bold) in
wastewater, soil and plant over the 6-month wastewater
treatment
134
Table 5-1 Experimental design to examine effects of idle period on
treatment efficiencies of mangrove wetland with 5-day HRT
139
Table 5-2 Effects of idle period on wastewater removal percentage (in
% except nitrate) during the two periods of wastewater
treatment
143
Table 5-3 Two-way ANCOVA results (F-value) on concentrations of
DOC, NH3-N, NO3--N, inorganic-N, inorganic-P, and TKN
in effluent from microcosms during the two treatment
143
List of Tables xxiii
periods
Table 5-4 Growth of A. corniculatum before and after the first and
second periods of wastewater treatment
151
Table 5-5 Percentage increase of biomass of A. corniculatum during
the first and second treatments
151
Table 5-6 Percentage increase of nitrogen concentration and uptake of
A. corniculatum during the first and second treatments
159
Table 5-7 Percentage increase of phosphorus concentration and uptake
of A. corniculatum during the first and second treatments
160
Table 5-8 Background properties of mangrove soil used in the first and
second treatment periods
162
Table 5-9 Changes in nutrients concentration per wastewater loadings
in soil after the first and the second wastewater treatment
periods
164
Table 5-10 Two-way ANOVA results showing effects of a period of idle
and plant on the percentages of changes in concentrations of
nitrogen elements (NH4+, NO3
-, Inorganic N and TKN) per
wastewater loading after the 6-month wastewater treatment
164
Table 5-11 Two-way ANOVA results showing effects of an idle period
and plant on the percentages of changes in concentrations of
168
List of Tables xxiv
phosphorus elements (PO43-, TP) per wastewater loadings
after the first and second wastewater treatment periods
Table 5-12 Two-way ANOVA results showing effects of idle and plant
on the percentages changes in concentration of total organic
matter per wastewater loadings, denitrification potential and
dehydrogenase activity in systems after the first and the
second wastewater treatment periods
169
Table 5-13 Microbial activities (dehydrogenase activity and
denitrification potential) in mangrove soil at the end of the
first and second treatment periods
169
Table 5-14 Amount of input and output nitrogen from wastewater, soil
and plant during the first and second wastewater treatment
171
Table 5-15 Mass balance of nitrogen (mg) and percentages of individual
part of nitrogen to total nitrogen (in bold) in wastewater, soil
and plant during the first and second wastewater treatment
periods
172
Table 5-16 Amount of input and output phosphorus from wastewater,
soil and plant during first and second wastewater treatment
periods
173
Table 5-17 Mass balance of phosphorus (mg) and percentages of
individual part of phosphorus to total phosphorus (in bold) in
wastewater, soil and plant during the first and second
174
List of Tables xxv
treatment periods
Table 5-18 Percentages of effluents fulfilling the different levels of
discharge standards in Hong Kong
177
Table 6-1 Average removal efficiencies (%) of dissolved organic
carbon (DOC) and nutrients from primary settled wastewater
184
Table 6-2 Nutrient content in three mangrove species at the beginning
191
Table 6-3 Nutrient content in three mangrove species in the end of the
experiment
196
Table 6-4 Changes of concentration of nutrients and total organic
matter in soil after wastewater treatment
199
Table 6-5 Amount of input nitrogen from wastewater, soil and plant
over the four-month wastewater treatment
206
Table 6-6 Amount of output nitrogen from wastewater, soil and plant
over the four-month wastewater treatment
206
Table 6-7 Mass balance of nitrogen (mg) and percentages of nitrogen
in each component (wastewater, soil and plant) to total
nitrogen (in bold) over the four-month wastewater treatment
207
Table 6-8 Amount of input phosphorus from wastewater, soil and plant
over the four-month wastewater treatment
208
List of Tables xxvi
Table 6-9 Amount of output phosphorus from wastewater, soil and
plant over the four-month wastewater treatment
208
Table 6-10 Mass balance of phosphorus (mg) and percentages of
phosphorus in each component (wastewater, soil and plant)
to total phosphorus (in bold) over the four-month wastewater
treatment
209
Table 6-11 Comparison of concentration of nitrogen and phosphorus
(mg g-1) in different plant tissues
213
Table 7-1 Removal efficiencies (%) using artificial saline municipal
wastewater
221
Table 7-2 Growth and biomass of A. corniculatum before and after
wastewater treatment
226
Table 7-3 Nutrient status in A. corniculatum before and after
wastewater treatment
229
Table 7-4 Changes of nutrients concentration in soil after wastewater
treatment
233
Table 7-5 Changes of concentration of TOM, denitrification potential
and dehydrogenase activity in soil after wastewater treatment
236
Table 7-6 Amount of input nitrogen from wastewater, soil and plant
over the four-month wastewater treatment
240
List of Tables xxvii
Table 7-7 Amount of output nitrogen from wastewater, soil and plant
over the 4-month wastewater treatment
240
Table 7-8 Mass balance of nitrogen (mg) and percentages of individual
part of nitrogen to total nitrogen (in bold) in wastewater, soil
and plant over four-month wastewater treatment
241
Table 7-9 Amount of input phosphorus from wastewater, soil and plant
over the four-month wastewater treatment
242
Table 7-10 Amount of output phosphorus from wastewater, soil and
plant over the four-month wastewater treatment
242
Table 7-11 Mass balance of nitrogen (mg) and percentages of individual
part of phosphorus to total phosphorus (in bold) in
wastewater, soil and plant over the four-month wastewater
treatment
243
Table 7-12 Percentages of effluents complied with discharge standards
at different water bodies in Hong Kong set by the
Government
246
List of Figures xxviii
List of Figures
Fig. 2-1 Free water surface flow system
34
Fig. 2-2 Subsurface flow system
34
Fig. 3-1
Schematic diagram of a constructed mangrove tank system
showing the inlet, treatment and outlet zones
51
Fig. 3-2 Concentrations of dissolved organic carbon (DOC) in
influent and effluent from different treatments during the
6-month wastewater application
64
Fig. 3-3 Concentrations of ammonia in influent and effluent from
different treatments during the 6-month wastewater
application
66
Fig. 3-4 Concentrations of nitrate in influent and effluent from
different treatments during the 6-month wastewater
application
67
Fig. 3-5 Concentrations of inorganic nitrogen in influent and effluent
from different treatments during the 6-month wastewater
application
69
Fig. 3-6 Concentrations of TKN in influent and effluent from
different treatments during the 6-month wastewater
application
70
List of Figures xxix
Fig. 3-7 Concentrations of inorganic phosphorus in influent and
effluent from different treatments during the 6-month
wastewater application
72
Fig. 3-8 Concentrations of TP in influent and effluent from different
treatments during the 6-month wastewater application
73
Fig. 3-9 Growth of mangrove plants during the 6-month wastewater
treatment (a) Stem height; (b) leaf number; (c) branch
number
78
Fig. 3-10 Nutrient concentrations in soil before (March) and after
(September) the 6-month experiment: (a)ammonium; (b)
nitrate; (c) inorganic nitrogen; (d) TKN
81
Fig. 3-11
Nutrient concentrations in soil before (March) and after
(September) experiments: (a) Inorganic P; (b) TP
85
Fig. 3-12
Two-way ANOVA results showing effects of hydraulic
retention time (HRT) and plant on the percentage of changes
of TOM to initial concentration, denitrification potential and
dehydrogenase activity in soil in mangrove tanks after the
6-month wastewater treatment
87
Fig. 4-1
Mean concentrations of DOC in effluent from different
systems during the 6-month wastewater treatment
110
List of Figures xxx
Fig. 4-2 Mean concentrations of ammonia-N in effluent from
different systems during the 6-month wastewater treatment
112
Fig. 4-3 Mean concentrations of nitrate-N in effluent from different
systems during the 6-month wastewater treatment
113
Fig. 4-4 Mean concentrations of inorganic N in effluent from
different systems during the 6-month wastewater treatment
114
Fig. 4-5 Mean concentrations of TKN in effluent from different
systems during the 6-month wastewater treatment
115
Fig. 4-6 Mean concentrations of inorganic P in effluent from different
systems during the 6-month wastewater treatment
117
Fig. 4-7 Growth of mangrove plants during 6-month wastewater
treatment (a) stem height; (b) branch number; (c) leaf
number
119
Fig. 4-8 Nitrogen concentrations in soil before (march) and after
(September) experiments: (a) ammonium; (b) nitrate; (c)
inorganic nitrogen; (d) TKN
124
Fig. 4-9 Phosphorus concentrations (inorganic P and TP) in soil
before (March) and after (September) wastewater treatment
126
Fig. 4-10 Total organic matter in soil before (March) and after
(September) wastewater treatment
128
List of Figures xxxi
Fig. 5-1 Mean concentrations of DOC in effluent from different
systems during the two periods of wastewater treatment
142
Fig. 5-2 Mean concentrations of ammonia in effluent from different
systems during the two periods of wastewater treatment
144
Fig. 5-3 Mean concentrations of nitrate in effluent from different
treatments during the two periods of wastewater treatment
146
Fig. 5-4 Mean concentrations of inorganic N in effluent from
different systems during the two periods of wastewater
treatment
147
Fig. 5-5 Mean concentrations of TKN in effluent from different
systems during the two periods of wastewater treatment
148
Fig. 5-6 Mean concentrations of inorganic P in effluent from different
systems during the two periods of wastewater treatment
149
Fig. 5-7 Plant biomass in terms of roots, stems and leaf before and
after wastewater treatment during the first and second
treatment periods
152
Fig. 5-8 N concentrations in terms of roots, stems and leaf before and
after wastewater treatment during the first and second
treatment periods
153
Fig. 5-9 P concentrations in terms of roots, stems and leaf before and 154
List of Figures xxxii
after wastewater treatment during the first and second
treatment periods
Fig. 5-10 N amount in terms of roots, stems and leaf before and after
wastewater treatment during the first and second treatment
periods
155
Fig. 5-11 P amount in terms of roots, stems and leaf before and after
wastewater treatment during the first and second treatment
periods
156
Fig. 5-12 Growth of mangrove plants over the first and second periods
of wastewater treatment (a) stem height; (b) leaf number; (c)
branch number
157
Fig. 5-13 Nutrient concentrations in soil in the beginning and end of
the first and second periods: (a) ammonium; (b) nitrate; (c)
inorganic nitrogen; (d) TKN
163
Fig. 5-14 Inorganic P and TP concentrations in soil in the beginning
and end of the first and second periods
167
Fig. 5-15 Total organic matter concentrations in soil in the beginning
and end of the first and second periods
168
Fig. 6-1 Mean concentrations of dissolved organic carbon (DOC) in
effluent from different systems during the four-month
wastewater treatment
183
List of Figures xxxiii
Fig. 6-2 Mean concentrations of ammonia in effluent from different
systems during the four-month wastewater treatment
185
Fig. 6-3 Mean concentrations of nitrate in effluent from different
systems during the four-month wastewater treatment
185
Fig. 6-4 Mean concentrations of inorganic N in effluent from
different systems during the four-month wastewater
treatment
186
Fig. 6-5 Mean concentrations of TKN in effluent from different
systems during the four-month wastewater treatment
187
Fig. 6-6 Mean concentrations of inorganic P in effluent from different
systems during the four-month wastewater treatment
188
Fig. 6-7 Initial dried biomass in terms of root, stem and leaf in A.
corniculatum, B. gymnorrhiza and A. ilicifolius
190
Fig. 6-8 Growth in terms of stem height, leaf number and branch
number of the three mangrove species during the four-month
wastewater treatment
193
Fig. 6-9 Dried biomass in the end of the experiment (root, stem and
leaf of A. corniculatum, B. gymnorrhiza and A. ilicifolius)
194
Fig. 6-10 Nitrogen content in four systems before (March) and after 198
List of Figures xxxiv
(July) wastewater treatment
Fig. 6-11 Phosphorus content in four systems before (March) and after
(July) wastewater treatment
201
Fig. 6-12 Content of TOM in the four systems before (March) and
after (July) wastewater treatment
202
Fig. 6-13 Denitrification potential before and after wastewater
treatment
204
Fig. 6-14 Dehydrogenase activity before and after wastewater
treatment
204
Fig. 7-1 Mean concentration of DOC in effluent in systems planted
with A. corniculatum at different salinities
220
Fig. 7-2 Mean concentration of ammonia in effluent in systems
planted with A. corniculatum at different salinities
221
Fig. 7-3 Mean concentration of nitrate in effluent in systems planted
with A. corniculatum at different salinities
223
Fig. 7-4 Mean concentration of inorganic nitrogen in effluent in
systems planted with A. corniculatum at different salinities
223
Fig. 7-5 Mean concentration of TKN in effluent in systems planted
with A. corniculatum at different salinities
224
List of Figures xxxv
Fig. 7-6 Mean concentration of inorganic P in effluent in systems
planted with A. corniculatum at different salinities
224
Fig. 7-7 Growth of A. corniculatum after the four-month treatment of
wastewater at different salinities (a) 0 ppt; (b) 15 ppt; (c) 30
ppt
227
Fig. 7-8 Growth of A. corniculatum during the four-month
wastewater treatment in terms of stem height, leaf number
and branch number
228
Fig. 7-9 Concentration of nitrogen elements in the beginning (March)
and end of (July) wastewater treatment (a) ammonium, (b)
nitrate, (c) inorganic nitrogen and (d) TKN
232
Fig. 7-10 Concentration of phosphorus elements in the beginning
(March) and end (July) of wastewater discharge (a) inorganic
phosphorus, (b) total phosphorus
235
Fig. 7-11 Content of total organic matter in the beginning (March) and
end (July) of wastewater treatment
236
Fig. 7-12 Microbial activities in the beginning (March) and end (July)
of wastewater treatment (a) denitrification potential (b)
dehydrogenase activity
238
Abbreviations xxxvi
Abbreviations
Ac Aegiceras corniculatum
Ai Acanthus ilicifolius
ANCOVA analysis of co-variance
ANOVA analysis of variance
AnSBR anaerobic sequencing bath reactor
APs alkylphenols
APEs alkylphenol ethoxylates
AW artificial wastewater
Bg Bruguiera gymnorrhiza
BOD biological oxygen demand
COD chemical oxygen demand
FCs faecal coliforms
FIA flow injector analyser
GC-ECD gas chromatograph-electron capture detector
HRT hydraulic retention time
INT 2-p-iodophenyl-3-(p-nitrophenyl)-5-pheny tetrazolium chloride
Kc Kandelia candel
RW real wastewater
SC somatic coliphage
SPSS statistical package for social science
TKN total Kjeldahl nitrogen
TN total nitrogen
TOM total organic matter
TP total phosphorous
TSS total suspended solid
UASB upflow anaerobic sludge blanket
UAF upflow anaerobic filter