Tapping the Untapped Water‐Related Resources

Dan CW Tsang Civil and Environmental Engineering,

Hong Kong Polytechnic University

dan.tsang@polyu.edu.hk

http://www.cee.polyu.edu.hk/~dan_tsang

         

                                          

Stormwater Harvesting Blue‐Green Infrastructure in NDAs

Sustainable water management Flood retention lake

River park, etc Sustainable Urban Drainage Systems

at‐source, passive stormwater treatment facility

Bioswale (one of bioretention systems) attenuating runoff volume

improving coastal water quality

reclaiming water for non‐potable reuse

   

    

   

 

 

         

  

 

                

    

 

     

         

             

       

                                                                

Parameter Unit

Recommended water quality standards

(HK WSD, 2015)

SAMPLE 1 23‐AUG‐2013 14:00

SAMPLE 2 30‐AUG‐2013 09:20

SAMPLE 3 30‐AUG‐2013 09:35

SAMPLE 4 30‐AUG‐2013 09:50

SAMPLE 5 30‐AUG‐2013 10:05

SAMPLE 4 30‐AUG‐2013 09:50

E. coli cfu /100

mL Non detectable 60,000 27,000 35,000 78,000 37,000 78,000

Total residual chlorine

mg/L > 2 < 0.2 < 0.2 < 0.2 < 0.2 < 0.2 < 0.2

Dissolved oxygen mg/L ≥ 2 8.4 6.4 6.1 5.7 6.0 5.7

Suspended solids (SS)

mg/L ≤ 5 180 37 32 38 32 38

Colour Hazen unit ≤ 20 75.0 37.5 25.0 25.0 25.0 25.0

Turbidity NTU ≤ 5 66 10 6 6 8 6

pH pH Unit 6 – 9 7.3 7.1 7.1 7.1 6.9 7.1

Threshold Odour Number (TON)

TON ≤ 100 <1 1 1 1 1 1

Biochemical oxygen demand

mg/L ≤ 10 8 12 9 11 10 11

Ammonia as N mg/L as N ≤ 1 0.36 0.16 0.53 0.56 0.50 0.56

Total Surfactants mg/L ≤ 5 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 < 1.0

Surface Runoff Quality Stormwater Quality in Happy Valley

HK DSD. (2014). An integrated approach in flood prevention and water reclamation in a densely populated metropolitan: Will the innovation work? Paper presented at the DSD International Conference 2014, HK Drainage Services Department, Hong Kong.

      

      

 

      

    

    

                                            

Surface Runoff Quality Other priority pollutants

Pollutants Concentrations WHO Guidelines for

Drinking‐water Quality (WHO, 2011)

Zn 0.1 – 4.4 Pb 0.1 – 2.4 0.01

Metals Cu 0.08 – 0.9 2 (mg/L) Cd 0.01 – 0.8 0.003

Ni 0.01 – 0.5 0.07 Cr 0.01 – 0.1 0.05

2,4‐D 11.5 – 67 30 Herbicides

Isoproturon 0.05 – 0.2 9(µg/L)

MCPA 0.065 – 2.2 2 Sources: Fletcher et al. (2004); Lau et al. (2009); Gan et al. (2010); Lundy et al. (2012); MDA (2011); Zgheib et al. (2012); LeFevre et al. (2015)

                     

     

     

       

 

       

   

         

     

   

         

       

   

 

               

           

                         

                                

         

  

                                              

                    

                    

                

   Non‐potable Use Criteria Water Quality Criteria for Reuse of Treated Standards for Uncontrolled Irrigation, Water

Effluent for Flushing at Ngong Ping Features and Cooling Towers Parameter Limiting Standards

Colour ≦ 20 Hazen Unit

Ammonia Nitrogen ≦ 1 mg/l

Odour ≦ 100 TON

Dissolved Oxygen ≧ 2 mg/l

BOD5 ≦ 10 mg/l

Total Suspended Solids ≦ 10 mg/l

Turbidity ≦ 10 NTU

E.Coli ≦ 100 cfu/100ml

Total Residual chlorine ≧ 0.5 mg/l

Synthetic detergents ≦ 5 mg/l

Parameter Criteria

Turbidity

If Media Filtration is used, it shall not exceed: Average 2 NTU within a 24‐hour

period 5 NTU for 5% of the time within a 24‐

hour period 10 NTU at anytime If Membrane Filtration is used, it shall not exceed: 0.2 NTU for 5% of the time within a

24‐hour period 0.5 NTU at any time

Total Coliform

7‐day median not to exceed 2.2 MPN per 100 mL

Not to exceed 23 MPN per 100 mL in more than one sample in any 30‐day period.

Not to exceed 240 MPN per 100 mL in any sample

HK WSD. (2014). ACQWS Paper No. 14 – Treated Effluent Reuse at Ngong Ping.

                     

                          

Challenges Unsatisfactory nutrient removal in

typical bioretention systems Total phosphorus (TP): 80%

Total nitrogen (TN): 50%

NO3 ‐N leaching

Filter media for subtropical climate

High permeability ?

Medium to high surface area ?

Organic pollutants ?

Heavy metals ?

Bacteria ?

          

Bench‐Scale Bioretention Columns Column

Bacteria Removal (%) Bacteria Detached (%)

1st Infiltration 2nd Infiltration 1st Drainage 2nd Drainage

IOCS 58.3 12.8 1.4 2.9

PolyDADMAC‐IOCS 43.6 11.7 1.0 2.5

CTAB‐IOCS 49.1 25.8 1.5 2.7

Biochar 98.9 95.4 0.3 0.6

H2SO4 ‐biochar 99.8 97.9 0.2 0.6

H3PO4 ‐biochar 98.2 94.1 0.3 0.6

KOH‐biochar 99.7 92.8 0.1 4.5

Amino‐biochar 98.6 87.9 0.8 9.7

                             

                     

Rainfall in NDAs 3 Priority Areas: Anderson Road Quarry NDA, Hung Shui Kui NDA,

and Tung Chung New Town Extension

Acknowledgment: DSD colleagues, YK Ho (CE/LD), Richard Leung (SE/RD2), Tommy Ng (E/RD2)

Rainfall in NDAs

a No data available in 1996. b No data available in 1997. c No data available in 2015.

*No data available in 1996 at Hong Kong International Airport Station http://www.hko.gov.hk/cis/climat_e.htm

    

                    

   Pilot‐Scale Bioswale Tests

Design Manuals UK: SuDS Manual (2015) Australia: Bioretention Technical Design Guidelines (Ver 1.1) Singapore: ABC Waters Design Guidelines (Second Edition)

   Pilot‐Scale Bioswale Tests

                                      

             

          

        

                 

 

            

      

Way Forward Technical Guidelines for Bioswale Design in Hong Kong

Expected improvement in water quality

E. Coli, SS, DO, turbidity, colour, BOD5, NH3 ‐N, etc priority pollutants such as heavy metals and herbicides

Parameter Unit Recommended water quality standards E. coli cfu /100 mL Non detectable

Total residual chlorine mg/L ≥ 1 exiting treatment system;

≥ 0.2 at user end Dissolved oxygen in reclaimed water mg/L ≥ 2

Total suspended solids (TSS) mg/L ≤ 5 Colour Hazen unit ≤ 20 Turbidity NTU ≤ 5

pH 6 ‐ 9 Threshold odour number (TON) ≤ 100

5‐day Biochemical oxygen demand (BOD5) mg/L ≤ 10 Ammoniacal nitrogen mg/L as N ≤ 1 Synthetic detergents mg/L ≤ 5

              

   

           

     

     

     

         

Way Forward Technical Guidelines for Bioswale Design in Hong Kong

Design considerations

e.g., bioretention‐to‐catchment ratio, flow rate, water qualities

Engineered bioretention filter media

Maintenance requirement for bioswale

Service life of bioswale

Economic analysis and life cycle assessment

   Waterworks (Alum) Sludge

   

           

Waterworks (Alum) Sludge

Disposal of Special Waste at Landfills as of 2014

         

   

                     

Reusing Alum Sludge as Fill Materials

Process Flow Diagram

Acknowledgment: WSD colleagues, Thomas Chan (CE/CM), Irene Pang (SE/CM), Antonio Chan (E/CM)

      

 

   

                     

               

Performance Indicators Tests Standards (a) Site Formation (b) CLSM

Physical

Density BS EN 12390‐7, 2009 / 1.4‐ 2.1 g/cm3

Compressive strength BS EN 6717, 2001 >1 MPa / 0.35‐ 1 MPa 0.3‐ 2.1 MPa

Water absorption BS EN 772‐11, 2011 / /

Thickness swelling BS EN 772‐11, 2011 / /

Flowability ASTM D 6103, 2004 / > 200 mm

Stiffening time ASTM C403, 2008 / 3‐5 h

Chemical

TCLP EPA 1311, 1992 On‐site reuse On‐site reuse

SPLP EPA 1312, 1992 / /

Semi‐dynamic leaching ASTM C1308, 2008 / /

Analytical objects Instruments Chemical/ Spectroscopic Analysis

Mineralogy X‐ray Diffractometer Analysis (XRD) Crystallization enthalpy Thermogravimetric and Differential Scanning

Calorimetry (TGA/DSC) Hydration heat & rate Isothermal Conduction Calorimetry (ICC) Heavy metals Inductively Coupled Plasma‐Atomic Emission

Spectrometry (ICP‐AES) Microscopic Analyses

Interface morphology Scanning Electron Microscopy with Energy Dispersive X‐ray spectroscopy (SEM‐EDX)

Porous structure Mercury Intrusion Porosimetry (MIP)

        

         

                  

     Recycling as Fill Material Aggregate

(a) Optimizing Binder Formulation

OPC 90% AS

OPC+PFA(Class‐F) 90% AS

OPC+PFA(Class‐C) 90% AS

OPC+GGBS 90% AS

OPC+ISSA 90% AS

OPC+MOC 90% AS

MOC+PFA(Class‐F) 90% AS

MOC+GGBS 90% AS

MOC+SF 90% AS

MOC+ISSA 90% AS

(b) Optimizing Aggregate Formulation

OPClow 95‐97% AS

NAhigh 95‐97% AS (AS:NA=2:3) NAlow 95‐97% AS (AS:NA=3:2) RA 95‐97% AS (AS:RA=3:2) CBA 95‐97% AS (AS:CBA=3:2) CG 95‐97% AS (AS:CG=3:2)

               

   Recycling as CLSM CLSM with Various Sludge Content, Additives and Supplementary Materials

       

   Recycling as CLSM CLSM with Various Cementitious Materials

                

                                        

                                                                          

                           

                             

                         

         

Recycling as CLSM Binder Aggregate

(a) Recycling Alum Sludge as Substitute of Aggregate 0% AS OPC + PFA 80% NA

12.5% AS OPC + PFA 70% NA +10% AS 25% AS OPC + PFA 60% NA +20% AS 50% AS OPC + PFA 40% NA +40% AS

(b) Promoting Cement Hydration by Additive Incorporation Super‐P OPC + PFA 60% NA +20% AS NaHMP OPC + PFA 60% NA +20% AS NaOH OPC + PFA 60% NA +20% AS NaAlO2 OPC + PFA 60% NA +20% AS Na2SiO3 OPC + PFA 60% NA +20% AS CaCl2 OPC + PFA 60% NA +20% AS

Ca(NO3)2 OPC + PFA 60% NA +20% AS (c) Modifying Binder and Aggregate Formulation

GGBS OPC + GGBS 60% NA +20% AS SF OPC + SF 60% NA +20% AS

Binder x 2 OPC + PFA 45% NA +15% AS MOC MOC + PFA 60% NA +20% AS MgOCl MgOCl + PFA 60% NA +20% AS CSA CSA + PFA 60% NA +20% AS RA MOC + PFA 60% RA +20% AS CBA MgOCl + PFA 60% CBA +20% AS CG CSA + PFA 60% CG +20% AS

 Way Forward

23

Many Thanks for Your Time!