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Home , Constructed wetland, Hong Kong Wetland Park, Reed bed

Constructed for Treatment Nora F. Y. Tam Chair Professor of Biology City University of

8 November 2016 (DSD Forum) 1 Water Resources and Management

• problem  Large volume from domestic / municipal sources → hypoxia and eutrophication  from industrial sources / landfill → toxic  Degrade freshwater, coastal and marine ecosystems • Water shortage problem  Lack of clean water has always been an issue of environmental concern all over the world, especially for developing countries  China is encountering a SEVERE water shortage, due to both a large population and  Nearly 400 cities suffer from inadequate water supply (Beijing, Shanghai: severe water shortage) • Purify storm / waste water for water reuse

2 vs Conventional Treatment

Conventional Systems Wetland Systems

Steel Wind Land

Chemicals Seeds Sun

Concrete Electricity Microbes Plants Microbes

• Conventional Treatment • Constructed Wetland  Involve large capital  Environmentally friendly and investment versatile  High operation costs  Low-cost systems and easy to  Higher technical know-how maintain  Small villages would not  Low energy requirements and afford such expensive low C foot-print system  Reuse as re-circulated water and maintain sustainable use of water resource Constructed Wetland (CW)

• Artificial wetland  create to mimic processes found in natural wetland ecosystems through engineering design  maximize removal of pollutants from storm water or wastewater  Create and restore wetland  Enhance aesthetic values and • Control parameters like to maximize removal efficiency:  Plant species  Soil properties  and flow pattern  Pollution loading rates  Retention time Constructed Wetland: application • An accepted technology worldwide, low cost, low energy consumption and low maintenance • Feasible under various climatic conditions • Widely applied in treating different types of wastewater  Domestic and municipal  Storm water and runoff  Agricultural runoff  Industrial wastewater   Landfill  Hospital wastewater  Golf Club, tourist spots, hotels, etc.  Migration and remediation Types of Constructed Wetland

• Free water or Surface flow wetland (SF) • Subsurface flow wetland (SSF), also called zone, vegetated bed, vegetated submerged bed: SF  Horizontal flow  Vertical flow (water often discharged at large dose but intermittently, so water gradually soaked into substrate) • Hybrid: SSF  a combination of different types of CW Mechanisms of CW

• Plant uptake, accumulation, assimilation and metabolism • Transformation and degradation by micro- organisms (e.g. and ):   Soil particles (bio-films) • Retention / immobilization in media / substrate / sediment / soil:  Adsorption and sorption, e.g. binding of P by Al, Fe, Ca- oxides, hydroxides and organic matter  Oxidation and reduction  Ion precipitation and exchange Plant-media (substrate)-microbe- toxicant interaction

Toxicants immobilize and degrade in Plant detects soil/sediment/substrate toxicant

Toxicant uptake by plants Root exudates stimulate Release microbial community to and formation mineralize/degrade of plaque toxicant Railway Station

Hong Kong Wetland Park

Yuen Long Bypass Engineered ConstructedWetland () in Hong Kong Hong Kong Wetland Park

• Area: 64 ha. EMA (Ecological Mitigation Area)

• Purposes -bed Filter ~1 ha. – Wetland Park: conservation, education and tourism facility – Reed-bed Filter: storm water runoff polishing Bypass Floodway Engineered Wetland

• March 2001 – December 2003 • An area of 7 ha • Improve quality of flood water Reed-bed (4)

Sedimentation Constructed Wetland at Lok Ma Chou Railway Station

• An area of 5 ha • Polishing treated sewage and storm-water runoff • Additional area for habitat diversity Current CW initiated by DSD

• DSD is now also conducting research on using CW to treat overflow wastewater coming out from adjacent pumping station • system to treat combined sewage from villages at Ping Yuen River  started in 2015  initial result is promising

13 DSD R&D Study – Treat Village Sewage at Ping Yuen River using reedbed CW

120m x 20m Constructed Wetland

• Constructed in May 2015 • Monitoring in Progress 14 Constructed Wetlands for Storm water, Village sewage or Wastewater Polishing

Project Name Development Other use(s) Dominant Area purpose Hong Kong Urban Education, ~1 ha Wetland Park development sightseeing and conservation Yuen Long Bypass Drainage Flood control Phragmites ~7 ha Floodway Lok Ma Chau Spur Transport Conservation Phragmites ~5 ha Line Ping Yuen River Village sewage Water Phragmites 2400 m2 purification

Only Phragmites (蘆葦) is used in constructed wetlands for in Hong Kong and no other species have been explored Guanlan, Shenzhen Mainland Honghu Park, Shenzhen

Cyperus (纸莎草) Canna (美人蕉)

Phragmites (芦苇) Canna (美人蕉)

Longgang, Shenzhen Wanning, Hainan

Canna (美人蕉) Arundo (花叶芦荻) Heliconia (彩虹鸟)

Cyperus (纸莎草) Constructed Wetland Plants

• Most CW use freshwater plants:  (cattails)香蒲  Canna 美人蕉  Acorus 菖蒲  Scripus (bulrush)藨草  Cyperus莎草  Iris 鸢尾  Eichhornia (water hyacinths水浮蓮)  Phragmites (common reeds 蘆葦)  Others Common wetland plants

Phragmites australis (Pa) 香蒲 蘆葦 Typha (cattails)

Canna indica (Ci) Acorus calamus (Ac) 美人蕉 菖蒲 Problems with commonly used wetland plants

• Herbaceous plants • Strongly recommend for annual harvests • Restrict to fresh wastewater, plants would die off rapidly under chronic salt stress • Not suitable for our system uses seawater for flushing

9 How to solve the problems of common wetland plants?

• Use plants do not require routine harvesting, e.g. perennial woody wetland plants • Wetland plants can tolerate and pollutants • : common in our coastal areas and robust, develop physiological adaptations to overcome stressed environment: anoxia, fluctuating salinity and frequent tidal inundation

Great potential in constructed wetlands for wastewater treatment What are mangroves? • Unique inter-tidal wetland found in sheltered:  Tropical and sub-tropical shores  Transit zone between land and ocean (open system) • Ecological functions  Provide diverse , feeding and breeding sites for coastal and marine animals  Prime nesting and migratory sites for hundreds of bird species and • Receive inputs from:  regular tidal flushing  freshwater streams and/or rivers 21 22

Significant ecological values

Mangroves offer diverse habitats to support high biodiversity of plants, animals and

ZhuHaowen 2009 Mangroves in Mai Po RAMSAR

Education, research, ecotourism

25 Socio-economic values

• Provide livelihood • Wood and fuel • Furniture and building materials • Chinese medicinal herbs • Animal feed and human food • Dye and other materials • Ecotourism • Education • Research

26 Convenient waste dumping grounds, toxic pollutants leak to sediment

Direct sewage discharge to river channel, contaminates mangrove sediment

27 Mangrove: Green kidney

• Nature’s kidney in coastal environments: perform kidney-like functions • Retain water on land, prevents flooding in wet years and drought in dry years • Store and assimilate nutrients and useful chemicals • Remove harmful materials from water, dilute and filter pollutants from industrial and agricultural discharges, contaminated soil/sediment • Transform contaminants or toxic pollutants to less harmful materials • Mangrove plants are tolerant

28 Why Mangroves can be used as CW? • Nutrients in wastewater stimulate plant growth:  Mangroves have very high productivity and require nutrients • Mangrove plants can tolerate toxic pollutants  e.g., , toxic persistent pollutants (POPs) such as polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs), oil, etc. • Stressed inter-tidal environments with special adaptations  Fluctuating salinity and oxygen  Unstable substratum

29 True Mangroves in Hong Kong

Kandelia obovata (Ko) Acanthus ilicifolius (Ai) Aegiceras corniculatum (Ac) Bruguiera gymnorrhiza (Bg)

Lumnitzera racemosa (Lr) Avicennia marina (Am) Excoecaria agallocha (Ea) Heritiera littoralis (Hl)

Tolerance of Mangrove to Heavy Metals (% survival, out of 12 plants)

A. ilicifolius A. marina A.corniculatum B. gymnorhiza Control 100 100 100 100

T1 50 100 100 100

T2 25 75 75 100

T3 0 75 50 75

T4 0 50 25 50

T1: 50, 50 and 100 mg/kg Cu, Pb and Zn, respectively; T2: 2 times of T1; T3: 4 times of T1; T4: 6 times of T1 Mangroves were more resistant to PAHs than Phragmites, Bg was most tolerant

3.0 a Control a Control Treatment 1 2.5 2.5 ab Treatment 1 a Treatment 2 a a Treatment 2 a Treatment 3 b a a ab Treatment 3 b Treatment 4 2.0 2.0 b a ab c Treatment 4 c b 1.5 1.5 c d

1.0 1.0

a a a b Dry biomassDry of (g) Dry biomassDry of leaves (g) b bc a b 0.5 c 0.5 c c b a c

0.0 0.0 K. obovata B. gymnorrhiza A. marina P. australis K. obovata B. gymnorrhiza A. marina P. australis Leaf biomass Root biomass Control no PAH; T1: 1 mg/g for each of Fl (fluorene), Phe (phenanthrene), Ant (anthracene), Fla (fluoranthene), Pyr (pyrene), Chr (chrysene), BaP (benzo[a]pyrene) and BkF (benzo[k]fluoranthrene); T2: 2xT1; T3: 12xT1; T4: 24xT1 All Phragmites died in T3 and T4, Am died in T4, while Ko and Bg survived all treatments How Mangrove Plants Tolerate Toxic Pollutants?

● Extensive root system and large root biomass ● Specialized root anatomy (arenchyma tissues for ventilation) ● Release of oxygen (ROL) from root to surrounding, provide aerobic pockets in anoxic sediment for oxidation and detoxification ● Formation of iron plaque to immobilize pollutants ● Root exudates (organic acids) and root surface support diverse groups of POP-resistant and POP- degrading microbes

34 Root of Acanthus ilicifolius: arenchyma tissue and thick outer layers with suberized walls ESEM SM

Cross-section Less ROL

ESEM SM

Cross-section

More ROL 35 • Fe plaque is a mixture of crystalline and amorphous ferric hydroxides goethite and lepidocrocite • More ROL around the rhizosphere may induce more Fe plaque formed on root surface to immobilize pollutants 36 Without Fe plaque on With Fe plaque on root surface root surface

37 FW 9 16 16 5SW 8 14 14 7 12 12 10SW root d.wt) -1 6 10 10 5 4 8 8 3 6 6 2 4 4 1 2 2 0 0 0

Fe plaqueFe g (mg 0 15 30 45 60 75 0 15 30 45 60 75 0 15 30 45 60 75 Period (d) Period (d) Period (d) B. gymnorrhiza E. agallocha A. ilicifolius

Fe plaque formed on root surface could be induced by pollutants but varied among mangrove species

FW: Fresh Water, 5SW: Medium Synthetic Wastewater, 10SW: Strong Synthetic Wastewater Zn 0.14 FW 0.12 5MW 10MW 0.10 Mn 0.08 Regression coefficient 0.06 Y = 0.010*X + 0.042 0.04 R2 = 0.797*** 0.16 0.02 Conc. in of plaque Zn Fe 0.14 0.00 0 2 4 6 8 10 0.12 Conc. of Fe plaque 0.10 0.08 0.06 Y = 0.016*X + 0.008 0.04 0.02 R2 = 0.862*** Conc. of Mn in plaque Fe Conc. of Mn 0.00 0 2 4 6 8 10 Conc. of Fe plaque

Relationship between concentration of Fe plaque (mg/g dw) on root surface of B. gymnorrhiza and Zn and Mn immobilized in Fe plaque Same for Cr, Ni, Pb, Cu and Cd, also for other mangrove plants 1.0 E. agallocha 1.0 1.0 K. obovata 0.8 0.8 0.8

0.6 0.6 0.6

0.4 0.4 0.4

0.2 0.2 0.2

Immobilization of pollutants Immobilization of pollutants 0.0 Immobilization of pollutants 0.0 0 1 2 3 4 5 6 0 1 2 3 4 5 6 0 1 2 3 4 5 6 Formation of Fe plaque Formation of Fe plaque Formation of Fe plaque

Phenanthrene Pyrene Benzo(a) pyrene

Relationship between the formation of Fe plaque on root surface and immobilization of PAHs in Fe plaque Positive relationships also found between Fe plaque and immobilization of PBDEs, e.g. BDE-47, -99, -100, -153, -154, -209 Potential of constructed mangrove wetland for wastewater treatment

41 Constructed Mangrove Wetlands (Futian, Shenzhen)

Sonneratia (海桑） Kandelia (秋茄） Aegiceras (桐花树） Growth of Kandelia obovata (left hand) and Aegiceras corniculatum (right hand belt) in 2010

Close-up showing vigorous growth of Aegiceras corniculatum and unplanted control in 2015 Average effluent conc (mg/L）and removal % in 10-year treatment in Futian

Species COD BOD5 TN NH3-N TP SP

Influent 119.03 53.02 16.17 13.53 1.61 1.26

S. caseolaris 43.35 13.38 8.56 6.87 0.65 0.45 64.9% 75.5% 53.6% 52.6% 65.0% 69.2% A. corniculatum 37.75 13.61 7.98 6.00 0.45 0.32 67.8% 74.1% 55.1% 58.4% 74.5% 76.9%

K. candel 41.98 13.75 8.25 7.27 0.64 0.47 62.8% 73.8% 50.0% 45.2% 62.2% 64.8%

• Treatment performance satisfactory • >70% of samples meeting the discharge standard for COD (60 mg/L), BOD (20 mg/L), TN and NH3 (15 mg/L), >40% for TP (<0.5 mg/L) Constructed Non-mangrove Wetlands World-wide

+ 3- Vegetation* DOC NH3 TKN PO4 TP References Lg 68.9 NR** NR NR NR Ran et al. 2004 Pm 43 55.1 NR 36.9 NR Okurut et al. 1999 Sl 74 90 87 99 95 Soto et al. 1999 Cp 63.3 39 NR 16.4 36.9 Okurut et al. 1999 Pm & Tl 58.5 24.2 NR NR NR Kaseva 2003 Tl & Sa NR 50 37 82 90 Cameron et al. 2003 Average 61.5 51.7 62.0 58.6 74.0

* Lg, Lemna gibba, Pm, Phragmites mauritianus, Tl, Typha latifolia, Sl, Scirpus lacustris Sa, Scirpus acutis, Cp, Cyperus papyrus **NR, Not reported Removal efficiencies are comparable between Mangrove and non-mangrove CWs Computerized Tide-tanks Artificial shrimp and livestock Effluent / industrial wastewater

40 L SW for tidal flushing 1.0(L)x0.5(W)x0.15(D) m3 (0-30 ppt)

Outlet for effluent collection Storage Tank Tide-tank

Schematic diagram of constructed mangrove microcosms with tidal cycle (HRT= 5days, daily loading = 5.1 L, 12:12 High: Low tides) Different tidal cycles: (i) without, (ii) every two weeks, (iii) every week and (iv) every day Removal of in municipal wastewater by Kandelia under different

Salinity Influent Effluent Removal efficiency (ppt) (mg L-1) (mg L-1) (%)

0 25.00 0.20±0.07 99.19±0.30

15 25.00 2.21±1.85 91.18±7.41

30 25.00 4.81±2.87 80.78±11.50 Removal Phosphorous by Kandelia

Influent Effluent Removal efficiency Salinity (mg L-1) (mg L-1) (%)

0 ppt 5.00 0.06±0.03 98.81±0.67

15 ppt 5.00 0.01±0.01 99.73±0.16

30 ppt 5.00 0.05±0.03 98.91±0.59 Removal percentages of shrimp pond effluent by Ko and Ac under different tidal regime at 20 ppt (no tidal, once a day, once a week and once every 2 weeks)

Treatment Mean Concentrations Removal Efficiencies (mg L-1) (%)

DOC 5.32 - 9.66 98.39 – 99.11

Ammonia 21.95 – 49.31 83.56 – 92.03

Inorganic nitrogen 45.72 – 60.09 79.53 – 84.99

Inorganic P 0.041 – 0.100 99.85 – 99.94

Ammonia removal was poorer with less formation if daily tidal flushing was provided, due to less supply of oxygen; BUT Tidal regime did not have any significant effect on inorganic N, P and DOC removal Mangroves are efficient in removing heavy metals from industrial wastewater

More than 99% were removed from strong Fe3+, Zn2+, Pb2+, Cr6+ industrial wastewater and concentrations in effluent all met discharge standard in HK

Cu2+, Cd2+ 100% were removed by the three mangrove species

51 Mangroves are also effective in removing PAHs from wastewater as well as contaminated sediment

MDL:0.278ppb Phenanthrene Phenanthrene

) 1.0 ) 1.4 -1 -1 TA

g L TA g L

 T1 T1  1.2 ( ~100% 0.8 ( ~100% T2 T2 TN TN Influent 1.0 0.6 Concentration: 0.8 henanthrene 1 mg L-1 (ppm) henanthrene 0.4 0.6 All effluent of Phe 0.4 0.2 were in <1 ppb 0.2 Concentration of p 0.0 Concentration of p 0.0 September November January September November January Month Month (Kandelia obovata) (Excoecaria agallocha) Benzo(a) pyrene (MDL: 0.218ppb) was not detected in effluent from all treatments

Pyrene MDL:0.340ppb Pyrene 1.2 0.8

) TA -1 ) TA T1 -1 1.0 T1 ~100% g L T2 g L ~100% T2   0.6 TN TN Influent 0.8

0.6 0.4 Concentration: 0.15 mg L-1 (ppm) 0.4

0.2 All effluent of Pyr 0.2 Concentration of pyrene ( of pyrene Concentration

Concentration of pyrene ( of pyrene Concentration were in <1 ppb

0.0 0.0 September November January September November January Month Month (Kandelia obovata) (Excoecaria agallocha) Concentrations of Polycyclic Aromatic Hydrocarbons in the effluent from Ko (left hand side) and Ea (right hand side) with different tidal flushing regimes PBDEs (Polybrominated Diphenyl Ethers)

BDE-47 BDE-47 16 12

) TA -1 ) TA 14 -1 T1 T1 ~100% 10 T2 g L T2

 12 ~100% Influent (mg L TN TN 8 Concentration: 10

-1 BDE-47 8 6 12.96 μg L

6 4 4

2 2 Concentration of Concentration of BDE-47 ( of BDE-47 Concentration

0 0 September November January September November January Month Month (Excoecaria agallocha) (Kandelia obovata) BDE-209 was not detected in effluent from all treatments BDE-99 BDE-99 8 12 TA

) TA ) -1 -1 T1 T1 T2 Influent 10 ~100% ~100% T2 6 TN Concentration: TN 8 17.56 μg L-1 4 6 ~100% All effluent had 4 2 BDE-47 and -99 in -1 2 Concentration of pyrene (ng L (ng of pyrene Concentration <10 ng L L (ng of BDE-99 Concentration

0 0 September November January September November January Month Month (Excoecaria agallocha) (Kandelia obovata) Concentrations of Polybrominated Diphenyl Ethers (BDE-47 and BDE-99 and BDE-209) in the effluent from Ea (left hand side) and Ko (right hand side) with different tidal regimes Is constructed mangrove wetland better in performance than traditional wetland?

Removal Efficiency: Mangrove VS. Non-mangrove using microcosms in greenhouse Greenhouse Study: Simulation Mangrove Wetland (Tide-tank)

Wastewater inlet Wastewater outlet Seawater inlet

66cm Mangrove Plants in Greenhouse

Unplanted 桐花树 (Aegiceras 木榄 (Bruguiera control corniculatum) Ac gymnorrhiza) Bg Greenhouse Study: Simulation Non- mangrove Wetland

Inlet Outlet

66cm Non-mangroves in Greenhouse

Phragmites australis (Pa) Acorus calamus (Ac) Canna indica (Ci) 蘆葦 菖蒲 美人蕉 Artificial wastewater: Simulate domestic + industrial wastewater Nutrient/ Organic Concentration Heavy Concentration (mgL-1) (mgL-1) metal

DOC 60 Zn 5 TKN 45 Mn 5

+ NH4 -N 25 Fe 30

- NO3 -N 0.5 Cu 2

3- PO4 -P 5 Pb 1 Phenanthrene 1 Ni 1 Pyrene 0.5 Cr 0.5

Benzo[a]pyrene 0.1 Cd 0.1 Phenol 10 Mangrove VS. Non-mangrove: Organic matter and nutrients

+ 3- Vegetation DOC NH3 TKN PO4 TP

Non-mangrove 61.5 51.7 62.0 58.6 74.0

Mangrove 73.4 84.0 90.6 97.5 94.6

Mangrove > Non-mangrove Mangrove VS. Non-mangrove: Heavy metals

• Mangroves > non-mangroves • Heavy metals in mangrove treated effluent mostly fulfill national and HK standards, but Zn, Mn and Cu in non-mangrove effluent sometimes exceed the standard • No significant differences among different mangrove species but for non-mangrove, Phragmites蘆葦> Canna美人蕉> Acorus菖蒲

• Possible to use mangroves for water and wastewater purification, as well as revitalization of river channels Fengtan River in Futian, Shenzhen

Before revitalization During revitalization

Start planting mangroves along river banks

62 Fengtan River after Revitalization

63 DSD: Potential Site for Further Study – Ma On Kong, Yuen Long

Black Water due to Domestic/ Livestock Waste

64 Tung Chung New Town Extension (West)

Sediment Zone

Surface Runoff

Constructed Wetland

Storage Pond

65 Yuen Long South Potential Development Area

Constructed Wetland

Sewage Treatment Works

Treated Effluent

Constructed 66 Wetland Take Home Messages • Constructed wetland: feasible technology for water purification and recreation of wetland habitats for wildlife • Selection of plant species: tolerant? Remember mangroves • Single or multiple species? Mixed plants with mangroves and non-mangroves • Harvesting or trimming of plants? Avoid or not? • Salinity of water / wastewater? • Media / substrate / sediment / soil? • Water flow pattern? • Hydraulic retention time (HRT)? • Retention and saturation? • Life span? • Removal mechanisms: – Roles of different components – Substrate-plant-microbes-water-pollutants Thank you

E-mail: [email protected]

68 CW (mangroves mixed with non- mangroves) in Long gang, Shenzhen Constructed wetland site