1 Water sector applications: Microbubble applications: wastewater aeration, dispersed air flotation, ozone dosing, algal growth/carbon capture. Fluidic electricity generationWill ZimmermanProfessor of Biochemical Dynamical SystemsChemical and Process Engineering, University of Sheffield
2 Outline Why microbubbles: mass transfer and flotation Wastewater aerationPotential for replacing dissolved air flotationAlgal growth / carbon capture / wastewater plant integration => target energy positive and CO2 neutralOzoneFluidic electricity generator
3 Why microbubbles?Steep mass transferenhancement.Faster mass transfer -- roughly proportional to the inverse of the diameterFlotation separations small bubbles attach to particle / droplet and the whole floc rises
4 Fluidic oscillator makes microbubbles Concept for microbubble generationNo moving parts switchingFluidic oscillator60 micronbubbles froma microchip diffuser600 micron nozzle bank
5 Pilot scale: Experimental design Master-slave amplifier systemfor fluidic oscillatorSuprafilt layout for 30m^3/h
6 Energetics: Power consumption Oscillatory flow draws less power than steady flow at the same throughput!
11 Summarized findings: 7-1-09 Visualization studyOscillation frequencypower 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.
12 Update / planMixed liquor second set of pilot trials nearly ready to reportSecond set of clear water trials reproduced 2008 resultsCurrently changed over to Aquaconsult strip diffusers / awaiting thawPlanning sequencing batch reactor trials with Aecom Design BuildPlanning continuous flow mixed liquor trials with YW / Aecom at Leeds SouthYW funding for plans, Aecom knowledge transfer partnership “in the works”Stages of commercial projects envisagedRetrofit 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.PERMOX diffusers (180micron pores and non-biofouling) could decrease bubble size by factor of five so ~80% electricity reduction possible by tuning operating conditions.Microporous ceramic diffusers (20 microns) – potential for 98-99% electricity cost removal, but mixing issue.
13 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.
14 Microporous diffusers Original nickel-based microporous membrane ~£2k /m2Now works with microporous ceramic ~£ / m2Suprafilt and HP Technical Ceramics are collaborating with UoS on fabrication
15 Field trial campaignMicroporousdiffuserGrowing algaewith microbubblesAgreed 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 refurbishmentTrial to be conducted March – June 2010.12m2 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.Assess CAPEX and OPEX requirements
16 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 labComponentsAchievementsHow to get the ozone off the chip? Microbubbles!Prototype conceptual designField trial campaign
17 Ozone Kills! One ozone molecule kills one bacterium in water! Ozone dissolves inwater to producehydroxyl radicalsOne ozone molecule kills one bacterium in water!Hydroxyl radical attacks bacterial cell wall, damages it by ionisation, lyses the cell (death) and finally mineralises the contents.
18 Mass murder! Plasma needle treatment: 1 bar @ 1000’s 0C Results Plasma needle: ComparisonAutoclave treatment of E Coli:2 121°C for 20 minSome survivePlasma needle treatment:1 1000’s 0Cfor few secondsNo survivors
19 Ozone plasma microreactor in the lab. Upper plateElectrical connectionElectrodesFibre opticsChipholder constructLower plate
20 Microfluidic onchip ozone generation Emission UV-Vis spectrum of exit gas with clear O3 signature. Analysis suggests 30% conversion at temperature 350K.Our new chip design and associated electronics produce ozone from O2 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 (170V, can be mains powered).
21 Modular integrated microchip concept for water treatment Essential electronicsSchematic microchipMicrofluidic device:Ozone plasma reactor + microbubblegenerator to be submerged (with shroudProtecting connections)Power source and matching networkin printed circuit board above water.Two wires and one air feed lineConnecting to microfluidic device.Note: conventional plasma sources cost ~£12000.Our low power, bespoke and tuned electronics cost about £100 in materials.
22 Plasma disks25 plasma reactors each with treble throughput over first microchip
23 Dosing lance assemblyThe top view of the lance (8 reactors above, 8 reactors below), separate oscillator branchesAxial view of the lance
24 Corporation cock assembly Valve control to toggle for flow/no flowExternal assembly.Ball valve
25 WTW tests on raw water Raw water inlet Upstream sample point for benchmarking water qualityand corporation cock to be fittedDownstream sample point for turbidity measurements. Sufficient for water quality study.
26 Potential markets Water purification (municipal) Waste water – organics removalWaste water – disinfection before releaseSterilization (medical, biotech, pharmaceutical)Distributed / remote / portable water purificationVentilation system sterilizationGas analysis (ozonolysis) and sensors
27 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.Journal article has won the 2009 IChemE Moulton Medal for best publication in all their journals.Designed for biofuels productionFirst use: microalgae growthCurrent TSB / Corus / Suprafilt grant on carbon sequestration feasibility study on steel stack gas feed to produce microalgae.
28 Construction Top with lid Inner view: Heat transfer coils separating riser /downcomer.FoldedperforatedPlate m-bubblegenerator.Replaced bySuprafilt 9inch diffuserBody / side view
30 With Fluidic Oscillator Without Fluidic Oscillator ResultsCHLOROPHYLL CONTENT (μg/ml)DAYSWith Fluidic OscillatorWithout Fluidic Oscillator10.530.5820.860.6130.980.6641.361.4551.341.771.902.3382.232.7292.803.04103.102.39113.432.83Rapid pH dropPotential licensee for carbonSequestration organic chemistryBest poster 6th Annual bioProcessUKConference, Nov 2009, York.30% higher relative growth rate with only60 minutes per day dosingTSB / Corus / Suprafilt project for continurous dosing.
31 Prospects for process integration / intensification for WWTW flowsheet re-design Anaerobic digestor: CO2 dosing and CO2/CH4 stripping Accelerates biochemistry CHP provides CO2 for algal growthKey concept: Microbubble dosing will be cheap, but allow access to all process gases.Anammox process Stage 1 Aerobic (air dosing) Stage 2 Anaerobic CO2 dosing and CO2/N2 strippingResult: Accelerate biochemistry of all processes by reactive extraction. Influence production by nutrient dosing rate. Grow algae for biomass / biofuel. Sequester CO2. Provide O2.
32 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 Found 150microWatts from flows rates typical of tap water.We have a similar approach but with our key feature have been able to achieve 1.5mW with same flow rates and can apply standard approach for another factor of 5-10 increase.
33 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 CO2 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 lanceAir lift loop bioreactor development for biofuelsHeterogeneous chemical and bioreactor engineering, gas-lift oil recovery, oil-water separations, heat transfer