Development of Integrated Filtration System for Water Treatment and Wastewater Reclamation in Developing Countries

Transcription

1 Development of Integrated Filtration System for Water Treatment and Wastewater Reclamation in Developing Countries C. Chiemchaisri Department of Environmental Engineering Faculty of Engineering, Kasetsart University, Bangkok 19, Thailand

2 Introduction - Bangkok, like other mega cities in developing countries, is suffering from the shortage of water resources due to the deterioration of natural water qualities. - To overcome these problems, efficient water treatment systems for producing good quality water supply and treated wastewater for reuse are needed. - Integrated filtration system employing floating media filter coupled with conventional sand/ zeolite filter or membrane filtration was developed for water treatment and wastewater reclamation purposes.

3 Integrated Filtration System - Filtration is an essential unit for solid separation in conventional water treatment and tertiary wastewater treatment processes. - Its applications include direct filtration of low turbidity water or filtration of coagulated water for high turbidity water. - In this study, floating media filtration system coupled with coarse c sand filter/ zeolite bed/ microfiltration membrane was applied d to the treatment of surface water and secondary effluent. - The advantages of system include smaller footprint comparing to conventional water treatment processes, high treatment efficiency and low operating cost.

4 Floating media filter coupled with coarse sand filter or zeolite bed for surface water treatment and wastewater reclamation

5 Floating media filter coupled with microfiltration membrane for surface water treatment

6 Polypropylene bead Laboratory scale experimental unit Hollow fiber membrane module

7 Pilot scale testing at Bangkhen water treatment plant Floating media filter Microfiltration membrane unit

8 Research series on Integrated Filtration System 1. Floating media/coarse sand filter for surface water treatment (lab scale) - turbidity removal 2. Floating media filter coupled/zeolite bed for wastewater reclamation (lab scale) - turbidity, N, P removals 3. Floating media filter/mf membrane for surface water treatment (lab scale) - turbidity, NOM, microorganism removals 4. Floating media filter/mf membrane for surface water treatment (pilot scale) - turbidity, NOM removals

9 Floating media filter/coarse sand filter for surface water treatment - Coagulants - Filtration rates - Media depth Alum, FeCl 3, PACl, polymer 5,8,12 m 3 /m 2.h 6:2, 5:3, 4:4, 3:5, 2:6 cm and 1.5 m of floating media filter alone Key findings Appropriate filtration rate of the system was found to be 5 m 3 /m 2.h, It was limited by the particle retention capacity of floating media filter and headloss development in coarse sand filter When only floating media filter of 1.5 m was used, the filtration rate of 15 and 1 m 3 /m 2.h could be maintained to obtain satisfied effluent turbidity level in long term operation.

10 Turbidity removal and headloss development: Effect of filtration rate Turbidity (DFF) (NTU) m/h 8m/h 12m/h Turbidity (DFF+CSF) (NTU) m/h 8 m/h 12 m/h Filtration time (h) Filtration time (h) Headloss (DFF) (cm) m/h 8m/h 12m/h Headloss (DFF+CSF) (cm) m/h 8 m/h 12 m/h Filtration time (h) Filtration time (h)

11 Turbidity removal and headloss development: Effect of bed depth Turbidity (DFF) (NTU) :2 5:3 4:4 3:5 2:6 Turbidity (DFF+CSF) (NTU) :2 5:3 4:4 3:5 2: Filtration time (h) Filtration time (h) Headloss (DFF) (cm) :2 5:3 4:4 3:5 2:6 Headloss (DFF+CSF) (cm) :2 5:3 4:4 3:5 2: Filtration time (h) Filtration time (h)

12 Relationship between L/d and turbidity removal in plastic media pre-filter Turbidity removal (%) mm 6 mm 8 mm bed depth:media size(l/d)

13 Floating media filter/ zeolite bed for wastewater reclamation - Direction filtration of secondary effluent from sewage treatment plant (particle removal) - Chemical precipitation (for P removal) using FeCl 3 and zeolite bed (for N removal) Key findings - Filtration rates - Media depth 1,3,5 m 3 /m 2.h 4:4 cm A filtration rate of 5 m 3 /m 2.h was proposed for direct filtration mode (only turbidity removal) whereas 1 m 3 /m 2.h was recommended for N, P removal from secondary effluent.

14 Treated water qualities for N, P removal and breakthrough period Parameters Std. Limit 1(m 3 /m 2.h) 3 (m 3 /m 2.h) 5 (m 3 /m 2.h) Eff. Hours Eff. Hours Eff. Hours SS (mg/l) < 5.4 > Turbidity (NTU) < 5.2 > NH 4 + (mg N/l) <5.9 > PO 4 3- (mg P/l) <.5.2 > Effluent Parameters Influent Range Average % Removal ph SS (mg/l) Turbidity (NTU)- DFF Turbidity (NTU)- Overall BOD (mg/l) NH + 4 (mg N/l) PO 3-4 (mg P/l)

15 Floating media filter/mf membrane for Surface water treatment Floating Media Filter - Acrylic column of 1 cm. diameter and 18 cm. long - Plastic media: Polypropylene (PP) bead of 3.6 mm diameter 1 m. bed depth Microfiltration Membrane Unit - Hollow filter membrane module with.1 μm m pore size and.2 m 2 surface area Filtration rate 5, 1, 15 m 3 /m 2.h Coagulant Polyaluminum chloride (PACl) at 25%, 5% and 1% of jar test Key findings Floating media filter was effective in promoting flocculation and a removing solid particles from raw water Low filtration rate (5 m 3 /m 2.h) was preferred to prevent breakthrough and reduce the solid particle loading to MF membrane

16 Particle removal in floating media filter (RW turbidity 8 NTU) Turbidity (NTU) PACl 8 mg/l PACl 4 mg/l PACl 2 mg/l Time(min) V = 5 m/hr Opt. dose 1% Opt. dose 5% Breakthrough of particles Turbidity(NTU) PACl 8 mg/l PACl 4 mg/l PACl 2 mg/l Time(min) V = 1 m/hr Turbidity(NTU) PACl 8 mg/l PACl 4 mg/l PACl 2 mg/l Time(min) V = 15 m/hr

17 SS(mg/l) min 24 min 36 min Depth(m) V = 5 m/hr PACl 8 mg/l Floc Size(um) min 24 min 36 min Release of small particles from floating filter Depth(m) V = 5 m/hr PACl 8 mg/l SS(m g/l) 1 8 Accumulation of solid particles In floating media filter min 24 min 36 min Depth(m) V = 1 m/hr 4 PACl 4 mg/l Floc Size(um) 3 2 Deeper accumulation In the filter bed 1 12 min 24 min 36 min Depth(m) V = 1 m/hr PACl 4 mg/l

18 Effect of turbidity and particle size on transmembrane pressure development of MF membrane Transmembrane Pressure(kPa) NTU V=.6 m/d V=1. m/d V=1.4 m/d V=5 m/hr V=1 m/hr DFF+MF MF Turbidity(NTU) Transmembrane Pressure(kPa) NTU V=.6 m/d V=1. m/d V=1.4 m/d V=5 m/hr V=1 m/hr MF DFF+MF Floc Size(um) MF membrane removed the remaining turbidity in water yielding constantc effluent turbidity. Transmembrane pressure development was low following the pretreatment by floating media filter

19 NOM removal in floating media filter/mf system Key findings High degree of NOM removal (>85%) was achieved in the system. Enhanced coagulation effect provided more than 8% of UV 254 removal in floating media filter. NOM removal results in significant reduction in chlorine demand and THM formation. Both turbidity and NOM concentration affected the fouling of membrane but TMP built up was mainly caused by particulate fouling

20 UV 254 removal during coagulation of river water UV removal (%) alum-medium turbidity 3 PACl-medium turbidity FeCl3-medium turbidity 2 alum-high turbidity 1 PACl-high turbidity FeCl3-high turbidity Coagulant dose (mg/l) PACl was found to be the most effective coagulant for NOM removal. Optimum dose was mg/l giving 75-9% UV 254 removal. 1 Relationship between turbidity and UV 254 removal in floating media filter UV removal (%) y =.8969x R 2 =.9578 y =.7213x R 2 = Turbidity removal (%)

21 Turbidity and NOM removal in floating media filter/mf system Condition Turbidity (NTU) UV 254 (cm -1 ) 1. PACl 1% 1.1 PP (7.5 m/h) MF (.3 m/d) 1.2 PP [11 m/h) MF (.45 m/d) 2. PACl 5% 2.1 PP (7.5 m/h) MF (.3 m/d) 2.2 PP (11 m/h) MF (.45 m/d) Avg. %Removal Avg. %Removal Parameters ph Turbidity (NTU) UV 254 (cm - 1 ) DOC (mg/l) Color (TCU) Range Value Avg

22 25 TMP (kpa) m/d-1%.3 m/d-1%.45 m/d-5%.3 m/d-5% Time (hours) TMP development in MF membrane unit Effect of raw water qualities (Turbidity and UV 254 ) on TMP development TMP increase (kpa) T.6 U.5 T1.3 U.3 T66 U.6 T16 U.16 T66 U.3 T16 U.3 Raw water qualities

23 Reduction in Cl 2 demand and THM formation.5 to 1. mg/l reduction in chlorine demand was achieved after removing NOM from the water. THM formation was reduced by 4-6% Sample Cl 2 dose (mg/l) CHLO ( g/l) DCBM ( g/l) DBCM ( g/l) Sum of THM ratio RW TW Sum of THM = C CHLO (WHO guideline) CHLO /GV CHLO CHLO + C DCBM DCBM /GV DCBM DCBM + C DBCM DBCM /GV DBCM DBCM + C BROMO BROMO /GV BROMO BROMO < 1

24 Water borne microorganism removal by floating media filter/mf membrane Key findings Freshwater algae was found partially removed by coagulation and entrapped in floating media filter but completely retained by MF membrane Total coliform and Fecal coliform was effectively removed by coagulation c and retained in floating media filter at low filtration rate (5 m/h) At higher filtration rate, total and fecal coliform removal efficiencies ficiencies were significantly reduced. Nevertheless, MF membrane helped removing the remaining TC and FC from water Coliphage was removed better in floating media filter operated at higher filtration rate but poorly retained by MF.

25 Microorganisms (MPN/1 ml, PFU/ml) Floating filter No coagulant: 5 m/h TC FC CP Microorganisms (x1 4 MPN/1ml, PFU/ml) Floating filter 14 (a) Turbidity (NTU) Microorganisms (MPN/1 ml, PFU/ml) with coagulant:5 m/h Operation Time (Hour) Improved FC removal improved CP removal No coagulant:15 m/h Microorganisms (MPN/1ml, PFU/ml) Operation Time (Hour) TC CP FC NTU penetration of CP Through MF (b) MF Turbidity (NTU) Operation Time (Hour)

26 Future research needs & possible collaboration - Investigation of trace pollutants (e.g. pesticide, pharmaceuticals) cals) contamination in surface water/treated wastewater in floating media and membrane filtration system - Enhancement of NOM removal by floating media bio-filtration or photo-oxidation oxidation associated with MF membrane for polluted water treatment - Detailed investigation of microorganism removal in floating media filter coupled with MF membrane treating actual river water. w - Implementation of full scale integrated filtration system at BangkokB waterworks and sewage treatment plants

27 Other research collaborations - Development of photosynthetic bacteria pond system for carbon recovery from industrial wastewater (with UT) - Investigation of reverse osmosis (RO) membrane fouling during reclamation of textile wastewater (WRPC & UT) - Application of membrane bioreactor (MBR) and RO system to solid waste leachate treatment (UT)

28 Full scale application of advanced leachate treatment system (1 m 3 /d) in Thailand

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