Application of Lanthanum-modified bentonite and flocculant reduces eutrophication in a lake

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1 Application of Lanthanum-modified bentonite and flocculant reduces eutrophication in a lake Guido Waajen Miquel Lurling Jeroen de Klein June 16, 2010 Jokioinen, Finland

2 Eutrophication has has become become the the primary primary water quality water issue quality for most issue of for the most freshwater of the and freshwater coastal marine and coastal ecosystems marine the ecosystems world in the world Smith & Schindler 2009 TREE 24: Smith and Schindler 2009 TREE 24: Symptoms: Massive Blooms Symptoms: Massive Blooms

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6 Problem: Cyanotoxins: health risk for humans, cattle, wildlife Decline biodiversity (e.g. disappearance macrophytes) Bad smell Visually unattractive Risk of fish kills (anoxia) Result: WFD qualification insufficient Swimming bans Complaints Costs

7 Year 19.0 Number of hits on blauwalg(en) Average summer temperature ( o C)

8 Strong reduction/prevention input nutrients Waste water treatment plants Sewer overflow systems Agricultural/urban run-off Prohibition of feeding animals (waterfowl, fish) Strong reduction of internal loading Biomanipulation (fishing= harvesting nutrients) Chemical fixation of Phosphorus Dredging

9 Many lake restorations, but: The failures are generally linked to insufficient or no decrease at all in the autochthonous or in-lake nutrient loadings Gulati & Van Donk 2002 Hydrobiologia 478: One of reasons for the lack of long-term effects may be internal phosphorus loading from a mobile pool accumulated in the sediment. Søndergaard & Jepessen et al Journal of Applied Ecology 44:

10 Diagnosis: Hyperphosphatemia

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12 Extremely low solubility lanthanum orthophosphate (rhabdophane): Ksp = to mol 2 l- 2 at 25 C (Johanneson & Lyons 1994; Liu & Byrne 1997) La 3+ + PO 4 3- LaPO 4 (s) Clay La 3+ PO 4 3- La 3+ PO 4 3- Clay Treated Untreated Low TP in watercolumn Strongly reduced P-release sediment PO 3- PO 3-4 PO PO 3- PO 3-4 PO 3-4 4

13 Untreated Flock & Lock treatment Cyanobacteria soup Rapid precipitation of algae Phosphate binding PO 4 3- PO 4 3- PO 4 3- Sediment capping PO 3-4 PO4 3-

14 Flock & Lock method Low dose flocculants (Flock) + Lanthanum modified bentonite (Lock) Cyanobacteria directly to sediment Immediately clear water, no toxins in water Phosphate permanently fixed Tackling bloom + internal loading

15 Quantity flocculant: testing in beakers Quantity of Phoslock: phosphorus in upper 5 cm sediment (Psenner) phosphorus in water Immediate avialable Fe/Mn bounded-p reductive soluble organic-p base soluble P - metaloxide bounded organic-p (microorganisms, humic, detritus) apatite/carbonate-p acid labile organic-p refractory organic-p 0.6 Core 1 Core 2 Core 3 Core 4 Core mg P g -1 sediment I 0-2 cm I 2-4 cm I 4-6 cm I 6-8 cm I 8-10 cm II 0-2 cm II 2-4 cm II 4-6 cm II 6-8 cm II 8-10 cm III 0-2 cm III 2-4 cm III 4-6 cm III 6-8 cm III 8-10 cm IV 0-2 cm IV 2-4 cm IV 4-6 cm IV 6-8 cm IV 8-10 cm V 0-2 cm V 2-4 cm V 4-6 cm V 6-8 cm V 8-10 cm Core slices

16 18 May 2009 FeCl 3 40% (4 ton) 19 May 2009 Phoslock (10 ton) Surface application 20/21 may 2009 Phoslock (30 ton) Deep injection flocculation [PO 4 3- ] flocks + ballast [Algae] Injection in hypolimnion Sedimentation aggregates PO 3-4 PO 3- PO Capping sediment

17 Lake De Kuil 7 hectares Average depth 4 m Maximum depth 8 m No point sources Total phosphorus (summer mean) 0,05-0,10 mg/l Total nitrogen (summer mean) 1-2 mg/l Chlorofyl-a max 160 µg/l Blooms of Cyanobacteria

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26 Before After

27 0 Flock & Lock Ice cover /01/09 06/01/09 05/01/09 04/01/09 06/01/10 05/01/10 04/01/10 03/01/10 02/01/10 01/01/10 12/01/09 11/01/09 10/01/09 09/01/09 08/01/09 Secchi depth (m)

28 Total chlorophyll-a Total Chlorophyll-a (µg/l) Flock & Lock 0-1 Water depth (m) Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

29 Cyanobacteria chlorophyll-a Cyano Chlorofyl-a (µg/l) Flock & Lock Water depth (m) Cyanobacteria chlorophyll-a -8 Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

30 Total Lanthanum (µg/l) Flock & Lock Totaal lanthaan (µg/l) 0-1 Water depth (m) Mar Apr May Jun Jul Aug Sep Oct Nov Flock & Lock Filterable Lanthanum (µg/l) 0-1 Water depth (m) Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar

31 Total P (µg/l) Water depth (m) A) Flock & Lock Filterable P (µg/l) Phosphate (µg/l) Mar Apr May Jun Jul Aug Sep Oct Nov 0-1 B) Flock & Lock Water depth (m) Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar

32 Total Iron (µg/l) Flock & Lock Totaal lanthaan (µg/l) 0-1 Water depth (m) Mar Apr May Jun Jul Aug Sep Oct Nov Filterable Iron (µg/l) Flock & Lock Water depth (m) Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar

33 Oxygen Zuurstof concentratie (mg/l) Flock & Lock 0-1 Water depth (m) Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

34 ph ph Flock & Lock 0-1 Water depth (m) Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

35 Temperature Temperatuur (oc) Flock & Lock 0-1 Water depth (m) Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr

36 Observation: colonies Microcystis near surface (July, Sept. 2009, May 2010)

37 Observation: increase macrophytes (Chara, Elodea, Potamogeton)

38 WFD-innovation project: mitigating Cyanobacteria nuisance Enclosure study Flock&Lock Lake De Kuil Compartments Compartments Sponsored by: Ministry of Economic Affairs, Province Noord-Brabant, Water boards Aa & Maas, Brabantse Delta, De Dommel

39 Conclusions first year De Kuil : No cyanobloom in 2009, low Chl-a Strong P-reduction Increased Sd, but turnover reduced Sd Increased macrophytes No anoxia September 2009: in hypolimnion low O 2, max Chl-a, Fe, P No swimming ban in 2009

40 Thank you!