Chemical Process Engineering Water sector applications Microbubble applications

Chemical & Process Engineering Water sector applications: Microbubble applications: wastewater aeration, dispersed air flotation, ozone dosing, algal growth/carbon capture. Fluidic electricity generation Will Zimmerman Professor of Biochemical Dynamical Systems Chemical and Process Engineering, University of Sheffield ‘Engineering from Molecules’

Outline • Why microbubbles: mass transfer and flotation • Wastewater aeration • Potential for replacing dissolved air flotation • Algal growth / carbon capture / wastewater plant integration => target energy positive and CO 2 neutral • Ozone • Fluidic electricity generator Chemical & Process Engineering ‘Engineering from Molecules’

Why microbubbles? Steep mass transfer enhancement. • Faster mass transfer -- roughly proportional to the inverse of the diameter • Flotation separations -- small bubbles attach to particle / droplet and the whole floc rises Chemical & Process Engineering ‘Engineering from Molecules’

Fluidic oscillator makes microbubbles Concept for microbubble generation Fluidic oscillator Chemical & Process Engineering No moving parts switching 60 micron ‘Engineering from Molecules’ bubbles from 600 micron nozzle bank ‘Engineering from Molecules’ a microchip diffuser

Pilot scale: Experimental design Suprafilt layout for 30 m^3/h Chemical & Process Engineering Master-slave amplifier system for fluidic oscillator ‘Engineering from Molecules’

Energetics: Power consumption Oscillatory flow draws less power than steady flow at the same throughput! Chemical & Process Engineering ‘Engineering from Molecules’

Visualization study and Frequency analysis With Oscillator Chemical & Without Oscillator Process Engineering ‘Engineering from Molecules’ With Oscillator, Master (small) shut completely ‘Engineering from Molecules’

Frequency of oscillation depends on feedback loop and air throughput Chemical & Process Engineering ‘Engineering from Molecules’

Aeration: DO profiles, clear water Blow-up Chemical & Process Engineering ‘Engineering from Molecules’

Delay time and dosage Chemical & Process Engineering ‘Engineering from Molecules’

Summarized findings: 7 -1 -09 • Visualization study • Oscillation frequency • power consumption: with maximum value of 18% reduction at the best aeration configuration. • Clear water dissolved oxygen study: 3 -4 fold better dosage at 83% of the design volumetric flow rate. • Mixed liquor dissolved oxygen study which showed markedly higher dissolved oxygen levels achieved in highly oscillatory dynamics for the control over the best oscillatory flow configuration. Indeterminate without BOD / metabolic activity assessment. Chemical & Process Engineering ‘Engineering from Molecules’

Update / plan • Mixed liquor second set of pilot trials nearly ready to report • Second set of clear water trials reproduced 2008 results • Currently changed over to Aquaconsult strip diffusers / awaiting thaw • Planning sequencing batch reactor trials with Aecom Design Build • Planning continuous flow mixed liquor trials with YW / Aecom at Leeds South • YW funding for plans, Aecom knowledge transfer partnership “in the works” Stages of commercial projects envisaged 1. Retrofit above ground “plumbing” of blowers with oscillators – saves ~18% electricity immediately + tuning for taking advantage of faster mass transfer with existing diffusers and submillimetre bubbles. 2. PERMOX diffusers (180 micron pores and non-biofouling) could decrease bubble size by factor of five so ~80% electricity reduction possible by tuning operating conditions. 3. Microporous ceramic diffusers (20 microns) – potential for 98 -99% electricity cost removal, but mixing issue. Chemical & Process Engineering ‘Engineering from Molecules’

Potential for dissolved air flotation (DAF) plant • Potentially eliminate recycle flow and saturator load (90 -95% electricity cost) • Uses blowers not compressors/saturators (much lower capital) • Cheap materials for retrofit with fluidic oscillators introduced in the plumbing and manifolds to diffuser bank for dispersal. Chemical & Process Engineering ‘Engineering from Molecules’

Microporous diffusers • Original nickel-based microporous membrane ~£ 2 k /m 2 • Now works with microporous ceramic ~£ 200 -300 / m 2 Suprafilt and HP Technical Ceramics are collaborating with Uo. S on fabrication Chemical & Process Engineering ‘Engineering from Molecules’

Field trial campaign Microporous diffuser Growing algae with microbubbles • Agreed with Northern Ireland Water and AECOM Design Build (Brenda Franklin) to trial the technology in a single DAF cell at Carmoney WTW which is undergoing refurbishment • Trial to be conducted March – June 2010. • 12 m 2 of surface area available for microporous diffuser insertion for retrofit. Unit instrumented to measure performance and to be outfitted with visualization equipment. • Tune performance in operating parameters – chiefly air throughput rates, water flow rate (~cm/s) and oscillation frequencies. • Model data from performance studies for engineering design parameters (number of plate diffusers, placement, flow rates). • Gain operational experience – identify potential problems, risks, failure modes -- to plan maintenance regime. Chemical & Process ‘Engineering from Molecules’ Engineering • Assess CAPEX and OPEX requirements

Ozone plasma microreactors: A proposition for commercial development for water and waste water treatment. • How ozone disinfects in water solutions. • The ozone plasma microreactor in the lab – Components – Achievements • How to get the ozone off the chip? Microbubbles! • Prototype conceptual design • Field trial campaign Chemical & Process Engineering ‘Engineering from Molecules’

Ozone Kills! Ozone dissolves in water to produce hydroxyl radicals One ozone molecule kills one bacterium in water! Chemical & Process Engineering Hydroxyl radical attacks bacterial cell wall, damages it by ionisation, lyses the cell (death) and finally mineralises the contents. ‘Engineering from Molecules’

Mass murder! Results Plasma needle: Comparison Autoclave treatment of E Coli: 2 bar @ 121°C for 20 min Some survive Plasma needle treatment: 1 bar @ 1000’s 0 C for few seconds No survivors Chemical & Process Engineering ‘Engineering from Molecules’

Ozone plasma microreactor in the lab. Upper plate Electrical connection Electrodes Fibre optics Chipholder construct Lower plate Chemical & Process Engineering ‘Engineering from Molecules’

Microfluidic onchip ozone generation Emission UV-Vis spectrum of exit gas with clear O 3 signature. Analysis suggests 30% conversion at temperature 350 K. Our new chip design and associated electronics produce ozone from O 2 with two key economic features: 1. Low power. Our estimates are a ten-fold reduction over conventional ozone generators. 2. High conversion. The selectivity is double that of conventional reactors (30% rather than 15% single pass). Additionally, it works at atmospheric pressure, at room temperature, and at low voltage (170 V, can be mains powered). Chemical & Process Engineering ‘Engineering from Molecules’

Modular integrated microchip concept for water treatment Essential electronics Schematic microchip Microfluidic device: Ozone plasma reactor + microbubble generator to be submerged (with shroud Protecting connections) Power source and matching network in printed circuit board above water. Two wires and one air feed line Connecting to microfluidic device. Note: conventional plasma sources cost ~£ 12000. Our low power, bespoke and tuned electronics cost about £ 100 in materials. Chemical & Process Engineering ‘Engineering from Molecules’

Plasma disks • 25 plasma reactors each with treble throughput over first microchip Chemical & Process Engineering ‘Engineering from Molecules’

Dosing lance assembly The top view of the lance (8 reactors above, 8 reactors below), separate oscillator branches Chemical & Process Engineering Axial view of the lance ‘Engineering from Molecules’

Corporation cock assembly Ball valve Chemical & Process Engineering External assembly. ‘Engineering from Molecules’ Valve control to toggle for flow/no flow ‘Engineering from Molecules’

WTW tests on raw water Raw water inlet Upstream sample point for benchmarking water quality and corporation cock to be fitted Chemical & Process Engineering Downstream sample point for turbidity measurements. Sufficient for water quality study. ‘Engineering from Molecules’

Potential markets • Water purification (municipal) • Waste water – organics removal • Waste water – disinfection before release • Sterilization (medical, biotech, pharmaceutical) • Distributed / remote / portable water purification • Ventilation system sterilization • Gas analysis (ozonolysis) and sensors Chemical & Process Engineering ‘Engineering from Molecules’

Air lift loop bioreactor design Schematic diagram of an internal ALB with draught tube configured with a tailor made grooved nozzle bank fed from the two outlets of the fluidic oscillator. The microbubble generator is expected to achieve nearly monodisperse, uniformly spaced, non-coalescent small bubbles of the scale of the drilled apertures. Chemical & Process Engineering • Journal article has won the 2009 IChem. E Moulton Medal for best publication in all their journals. • Designed for biofuels production • First use: microalgae growth • Current TSB / Corus / Suprafilt grant on carbon sequestration feasibility study on steel stack gas feed to produce ‘Engineering from Molecules’ ‘Engineeringmicroalgae. from Molecules’

Construction Top with lid Inner view: Heat transfer coils separating riser /downcomer. Folded perforated Plate m-bubble generator. Replaced by Suprafilt 9 inch diffuser Body / side view Chemical & Process Engineering ‘Engineering from Molecules’

ALB for algae growth Chemical & Process Engineering ‘Engineering from Molecules’

Results CHLOROPHYLL CONTENT (μg/ml) DAYS 1 2 3 4 5 7 Rapid p. H drop Potential licensee for carbon Sequestration organic chemistry 8 9 10 11 Best poster 6 th Annual bio. Process. UK Conference, Nov 2009, York. Chemical & Process Engineering With Fluidic Oscillator Without Fluidic Oscillator 0. 53 0. 86 0. 98 1. 36 1. 34 1. 90 2. 23 2. 80 3. 10 3. 43 0. 58 0. 61 0. 66 1. 45 1. 7 2. 33 2. 72 3. 04 2. 39 2. 83 30% higher relative growth rate with only 60 minutes per day dosing TSB / Corus / Suprafilt project for continurous dosing. ‘Engineering from Molecules’

Prospects for process integration / intensification for WWTW flowsheet redesign Key concept: Microbubble dosing will be cheap, but allow access to all process gases. Anaerobic digestor: CO 2 dosing and CO 2/CH 4 stripping Accelerates biochemistry CHP provides CO 2 for Anammox process algal growth Stage 1 Aerobic (air Result: Accelerate biochemistry dosing) of all processes by reactive extraction. Influence Stage 2 Anaerobic CO 2 production by nutrient dosing and CO 2/N 2 rate. Grow algae for biomass / stripping biofuel. Sequester CO 2. Chemical & Process ‘Engineering from Molecules’. ‘Engineering Provide O from Molecules’ Engineering 2

Remote fluidic electricity generator • Concept: Fluidic oscillator provides “AC” fluidic power. Piezoharvester converts to AC electricity. • Need: remote pipelines for parasitic electricity generation from flow energy. • No moving parts, fit and forget, power sensors and telemetry, potentially actuators. • German group published results in December 2008. Found 150 micro. Watts from flows rates typical of tap water. • We have a similar approach but with our key feature have been able to achieve 1. 5 m. W with same flow Chemical & rates and can apply standard approach for another Process ‘Engineering from Molecules’ Engineering factor of 5 -10 increase.

Potential microbubble markets • Dispersed air flotation for solids removal in water and wastewater (achieved target bubble size, 20 microns) • Wastewater aeration (partner YW, 18% energy reduction, 3 -fold higher dosing rates on retrofit) • Algal biomass / bioenergy production (partner Corus, >30% extra biomass from CO 2 microbubble dosing) • Wastewater treatment processes integration and intensification: aeration, digestion, de/nitrification, algal growth. Targets: smaller footprint; carbon and energy neutral! • Ozone dosing from a plasma microreactor dosing lance • Air lift loop bioreactor development for biofuels • Chemical Heterogeneous chemical and bioreactor engineering, gas& Process ‘Engineering from Molecules’ lift oil recovery, oil-water separations, heat transfer ‘Engineering from Molecules’ Engineering