Elektrochemische Desinfektion und Wasseraufbereitung in Aquakultur- Kreislaufsystemen mittels Diamantelektroden. MSc.

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1 Elektrochemische Desinfektion und Wasseraufbereitung in - Kreislaufsystemen mittels Diamantelektroden MSc. Chris van Bussel

2 EVA (Elektrochemische Verfahren in der ) -EVA project is funded by: -Project members: & Dr. Thorsten Matthee Dr. Barbara Behrendt-Fryda Dr. Matthias Fryda Linda Heesch MSc. Chris van Bussel Dr. Jan Schroeder Prof. Dr. Carsten Schulz

3 Project aim EVA Explorations for possibilities to use Boron Doped Diamond (BDD) electrodes cells for water treatment & disinfection in RAS.

4 What are Boron Doped Diamonds? carrier material + diamond layer including an impurity -Electrical conductive -Workable/editable -Chemical inert -Thermal inert -Hardness -Electrical Isolator -Semiconductor Niobium Carbon Boron

5 BDD cathoded + BDD anode - Gesellschaft für What are BDD electrodes? Carrier 100 Carbon (CH 4 ) 1 Boron (BF 4 ) OH H + e - (BDD) H 2 O + -

6 Hydroxyl radical Strong oxidant gain e - OH Oxidant (radical) formation O or OH addition (oxidation) H abstraction (H 2 0 formation) Electron transfer (e.g. XFe 4- XFe 3- ) Total Residual Oxidant formation: In fresh water O 3 H 2 O 2 In marine water (BDDTRO Cl-O x Br-O x I-O x Oxidant Fluorine 3.06 Hydroxyl Radical 2.80 Ozone 2.07 Hydrogen Peroxide Oxidant potential (V) 1.77 Permanganate 1.67 Hypochlorous Acid 1.49 Chlorine 1.36 Bromine 1.07

7 BDD electrodes in RAS? TRO (total residual oxidants) Strong oxidators Strong disinfectants Very toxic to fish Relation electrical current ( OH doses) and TRO formation? Do TRO accumulate? Is disinfection possible? Oxidation of (in)-organics? Is it possible to affect water quality within TRO safety levels??

8 Experimental set up Flow trough experiments Short term RAS experiments Long term RAS experiments: 30 days 12 tanks (4 * 3 replicates) Control Ozone Electrocell treatment 1 Electrocell treatment 2 Constant TRO Restricted feeding What are the effects on: TRO formation? water quality? bacterial pressure? production performance? bacterial/parasitic diseases?

9 TRO formation and accumulation Flow trough system current (A) vs.tro linear Easy to set TRO safety limit RAS TRO does accumulate Accumulation reaches plateau TRO production = TRO consumption

10 Effect on disinfection Flow trough system >99.9 % disinfection!! TRO formation only 0.2 mg/l RAS TRO limits applied dose 0-50 % disinfection No effect on bacterial pressure TAKE HOME MESSAGE: BDD-electrodes are very efficient in disinfection, but in RAS water doses is limited by TRO accumulation

11 Effect on accumulating substances in RAS Condiapure Control Condiacell Condiapure O 3 Condiacell

12 Are BDD-electrodes beneficial in RAS? Water parameter Cl - / Br - TAN NO 2 - NO TOC colour TP/PO 4 - Bacteria Effect found TRO chlorate bromate removed oxidized oxidized removed removed inactivated Effect on fish If removed???

13 Where to use BDD-electrodes in RAS? Disinfection Oxidation 1. Fire-wall 2. End-of-the-pipeline treatement 3. Treatment of whole waterflow 4. Bypass-treatment

14 Future research Optimize water treatment! Define targets to be oxidized Change electrocell / system design according to target Oxidation of off-flavours? Oxidation of hormones/pheromones? TAKE HOME MESSAGE: Formation and accumulation of TRO limits applied dose of hydroxyl radicals but water quality can be influenced within safety levels!

15 Verbreitung, Fortführung, Perspektiven Thank you for your attention! Questions?

16 Reaction rates on BDD electrodes in RAS Reaction speed = rate constant * concentration Molecule Rate constant OH (M -1 s -1 ) OH 4.0 * O * Cl- 1.5 * ClO2 1.1 * 10-9 Br- 5.0 * 10-9 BrO- 4.4 * 10-9 TOC (sucrose) 2.4 * 10-9 NO * 10-9 Factor (1st order, 20 C, hpa) RAS water Concentration (g/l) Cl Br O TOC 0.01 TP 0.01 TAN NO TRO < Factor

17 TRO formation and accumulation Gesellschaft für -Flow trough system

18 TRO formation and accumulation Gesellschaft für -Flow trough system

19 RAS water model RAS water matrix dependent on: Waste production (feed load * feed quality * feed utilisation) Waste removal (volume * efficiency) Water volume Water renewal rate Nutrient in feed Concentration (g/kg) Waste product in RAS water Concentration (mg/l) C 250 N 80 P 10 Ca 10 Minerals Fe,Zn,Mn,Cu,Co,... 1 CO 2 5 TOC 10 TP 10 TAN 1 NO 2 -N 1 NO 3- N 80 Minerals 0.1

20 Nitrogen removal on BDD-electrodes N 2 TAN NO 2 NO 3 N 2 Reaction orders TAN N2 -third order = interference -high TRO requirment - NO2 can also be formed NO3 N2 -third order = interference - slow - TRO is byproduct - TAN and NO2 can also be formed Alternative for safe nitrification / denitrification bio-processes?