Ochre Pelletising and use for phosphate Removal from sewage effluent 2 nd February 2005 Jonathan Aumônier

Introduction Pelletising Process Lab results – phosphate removal Micrographs Windlestone trial Planned work

Requirements for Pellets Physical Strength – (Crush and handling) Resistance to degredation in water Resistance to degredation through biological activity Size Retained Reactivity of Ochre Retained Phosphate Capacity High Porosity No “Film” or “Matrix” Binder System No Leaching of metals

Extrusion Trial ‘Z’ Blade Mixer-Extruder Cutting Extruded Product Mixer Blades

Pan Pelletising

Θ Water & Liquid Binder Powder Feed Water & Liquid Binder Powder Feed Small Pellets Large Pellets Product Pan Angle Θ Rotational Speed ω

Pelletising Equipment Vibrating Hopper Variable Speed Helical Feed Screw Dust Extraction 70cm Diameter Pelletising Pan ASDA Washing-up Bowl

Ochre Sources and use Skinningrove - initial physical test Silwood - MScs - 1 st Nafferton Farm trial Acomb - Current lab work - 2/3 of Windlestone pellets - Some to Leitholm Polkemet - 1/3 of windlestone pellets - Leitholm Horden - 1/3 of Leitholm - ESL Nafferton Farm - Stock of pellets

Phosphate remover from solution with varying initial P – after 24 hours Initial P (mg/l) P removed (mg/l) Data from Lawrence Bowden

Rate of phosphate sorption Time (s) Phosphate load on pellets (mg_P/g) Data from Lawrence Bowden

Rapid P Sorption tests Residence time (s) Solution Concentration (mg/l P) Feed Concentration 1 mg/l P Data from Frances Brett

Phosphate removed from solution with varying ionic strength of KCl Molar strength of solution KCl % Removal 100% 80% Data from Lawrence Bowden

Ochre pellet before reaction with phosphate solution x100

Ochre pellet before reaction with phosphate solution x800

Ochre pellet after reaction with phosphate solution x65

Ochre pellet after reaction with phosphate solution x100

Windlestone trial details (Horizontal Flow) Feed taken from site final effluent Initial rate 2.7 m 3 /hr reduced to 0.75 m 3 /hr 0.96 m 3 of pellets Contact time 7½min increased to 24 min Sampled input and output every 25 hr

Windlestone trial details (Vertical Flow) Feed taken from site final effluent Flow Rate 0.75 m 3 /hr 0.88 m 3 of pellets Mean contact time 90 second (unsaturated flow) Mean contact time 25 minutes (fully saturated flow) Sampled input and output every 25 hr

Ochre pellet reaction vessel: Windlestone WWTW – Horizontal Flow Images: Jonathan Aumônier Slide: Kate Heal Inflow Outflow Effluent percolates through ochre Gravel

Final STW Sump at Windlestone Inlet for Trial Outlet from Trial

Mono – Progressive Cavity Pump

Results for Windlestone Trial (Horizontal Flow) Date Removal Fraction Feed Phosphate Mg/l P

Windlestone spot results Results from samples after maintenance to clear the overflow Input P (mg/l) Output P (mg/l) Flow rate (m 3 /hr) % Removal

Ochre pellet reaction vessel: Windlestone WWTW – Vertical Flow Inlet Pipe From Pump In-line Strainer Spray Bars Inlet Sample Line

Ochre pellet reaction vessel: Windlestone WWTW – Vertical Flow Inlet m3/hr 500mm Saturated Zone U Bend Outlet Spray Bar

Results for Windlestone Trial (Vertical Unsaturated Flow) Date Feed Phosphate Mg/l P Removal Fraction 0.75 m 3 /hr mean residence time 90 sec Mean Removal 26%

Planned Work Continue Windlestone trial with saturated flow More locations Laboratory tests on ochres and binders Laboratory continual flow trials

Flow Columns in the Lab

Ochre pellet after reaction with phosphate solution x65