Removal of Positively Buoyant Planktothrix rubescens in Lake Restoration

The combination of a low-dose coagulant (polyaluminium chloride-'Floc') and a ballast able to bind phosphate (lanthanum modified bentonite, LMB-'Sink/Lock') have been used successfully to manage cyanobacterial blooms and eutrophication. In a recent 'Floc and Lock' intervention in Lake de Kuil (the Netherlands), cyanobacterial chlorophyll-a was reduced by 90% but, surprisingly, after one week elevated cyanobacterial concentrations were observed again that faded away during following weeks. Hence, to better understand why and how to avoid an increase in cyanobacterial concentration, experiments with collected cyanobacteria from Lakes De Kuil and Rauwbraken were performed. We showed that the Planktothrix rubescens from Lake de Kuil could initially be precipitated using a coagulant and ballast but, after one day, most of the filaments resurfaced again, even using a higher ballast dose. By contrast, the P. rubescens from Lake Rauwbraken remained precipitated after the Floc and Sink/Lock treatment. We highlight the need to test selected measures for each lake as the same technique with similar species (P. rubescens) yielded different results. Moreover, we show that damaging the cells first with hydrogen peroxide before adding the coagulant and ballast (a 'Kill, Floc and Lock/Sink' approach) could be promising to keep P. rubescens precipitated

The unfulfilled promise of urban Lake Kleine Melanen (The Netherlands): Diagnostics, experiment on reduction of sediment P-release and in-lake restoration

AbstractWaajen, G, Lürling M, van de Sande R. The unfulfilled promise of urban Lake Kleine Melanen (The Netherlands): diagnostics, experiment on reduction of sediment P-release and in-lake restoration. Lake Reserv Manage. 35:8–24.Lake Kleine Melanen (The Netherlands) experienced cyanobacterial blooms during the summertime, causing public health risks, turbid water, and lack of macrophytes. To improve the situation, we determined the underlying causes of the poor water quality. Our diagnosis included the water and phosphorus (P) budget of the lake and showed the need for the reduction of both the external and internal P loads. The external P load (7.5 mg P/m2/d) exceeded the transition between the clear water state and the turbid state by 44–121 mainly due to the discharges from the separated stormwater sewer system in the adjacent neighborhood. Due to political and financial considerations of the managing authorities, the restoration (2010–2012) was restricted to internal management. To reduce the high internal P load (3.8 mg P/m2/d), we tested 3 sediment capping options in an enclosure experiment, showing the best results when we combined sand capping with the P fixative Phoslock® and flocculant polyaluminumchloride. A 0.6–1.3 m thick layer of soft sediment was dredged from the lake. Thereafter, the sediment was capped with a 0.2 m thick layer of sand to which Phoslock® was added. Additional in-lake measures including fish removal and shoreline reconstruction were also conducted to support improvement. We compared water quality before (2008–2010) and after (2012–2014) interventions. Although the mean concentration of total P was reduced from 0.30 to 0.11 mg P/L, and cyanobacterial chlorophyll a from 52 to 6 μg/L, cyanobacterial blooms still occurred. For further water quality improvement, the reduction of the external P load caused by stormwater runoff is required

Application of Lanthanum-modi?ed bentonite and ?occulent reduces eutrophication in a lake

vokMTT, Viestintä ja informaatiopalvelut, 31600 Jokioine

Evaluation of several end-of-pipe measures proposed to control cyanobacteria

While reduction in nutrient loading is a prerequisite for mitigation of harmful cyanobacterial blooms in nutrient-enriched waters, in certain surface waters eutrophication control is not always feasible due to practical and economic constraints or might be effective only in the long run. Yet, the urgent need to control cyanobacteria in water for drinking, irrigation, aquaculture, industry and recreation has spurred the development of a plethora of alternative methods that claim to be fast acting. Here, we provide a critical overview of several of these end-of-pipe measures: effective microorganisms (EM®), golden algae (Ochromonas), plant/tree extracts, ultrasound and artificial mixing of non-stratifying waters. Most of the end-of the pipe measures claim to provide sustainable control of harmful cyanobacterial blooms, while at best only targeting symptom relief rather than eutrophication relief. Support for “effective” microorganisms, golden algae, plant extracts, ultrasound and artificial mixing of non-stratifying waters to diminish eutrophication problems such that the resulting water quality meets societal and legislation demands is limited, and several proposed underlying mechanisms are doubtful. None of these curative measures seem the desired wide applicable solution to cyanobacterial nuisance; they should not be considered Columbus’s egg. A critical evaluation of end-of pipe measures is crucial for water authorities in their choice for mitigating measures.</p

Effects of Dredging and Lanthanum-Modified Clay on Water Quality Variables in an Enclosure Study in a Hypertrophic Pond

An enclosure experiment was conducted between July and September 2009 to compare the effectiveness of a phosphate fixative, the lanthanum-modified bentonite clay Phoslock® (LMB), dredging, and their combination in controlling eutrophication in a hypertrophic urban pond in Heesch, The Netherlands. In total, 25 water quality variables were monitored. Multivariate analysis revealed that the combination LMB-treated and dredged enclosures deviated most from the pond (reference) and the controls, and showed the strongest eutrophication reduction. Overall, dredging significantly increased transparency, lowered turbidity, and improved the oxygen conditions in the enclosures compared to non-dredged ones. Nonetheless, one dredged enclosure deviated dramatically from the others, which might reflect methodological issues with dredging. The LMB treatment appeared to be less effective at mitigating eutrophication than dredging, and phosphate concentrations even increased during the experiment in the LMB-treated enclosures. Chemical equilibrium modeling suggested that humic substances could have formed complexes with lanthanum (La) from the LMB, rendering it unavailable for intercepting P over the course of the enclosure experiment. Residual lanthanum concentrations in combination dredging and LMB treatments exceeded the Dutch standard 10-fold. Total zooplankton abundance, and particularly Cladocera, increased in all enclosures over the course of the experiment. The limited effect of LMB in the enclosure experiment and the violation of the Dutch La standard when combined with dredging disqualify LMB as an intervention agent in the restoration of the pond

Effects of dredging and lanthanum-modified clay on water quality variables in an enclosure study in a hypertrophic pond

An enclosure experiment was conducted between July and September 2009 to compare the effectiveness of a phosphate fixative, the lanthanum-modified bentonite clay Phoslock® (LMB), dredging, and their combination in controlling eutrophication in a hypertrophic urban pond in Heesch, The Netherlands. In total, 25 water quality variables were monitored. Multivariate analysis revealed that the combination LMB-treated and dredged enclosures deviated most from the pond (reference) and the controls, and showed the strongest eutrophication reduction. Overall, dredging significantly increased transparency, lowered turbidity, and improved the oxygen conditions in the enclosures compared to non-dredged ones. Nonetheless, one dredged enclosure deviated dramatically from the others, which might reflect methodological issues with dredging. The LMB treatment appeared to be less effective at mitigating eutrophication than dredging, and phosphate concentrations even increased during the experiment in the LMB-treated enclosures. Chemical equilibrium modeling suggested that humic substances could have formed complexes with lanthanum (La) from the LMB, rendering it unavailable for intercepting P over the course of the enclosure experiment. Residual lanthanum concentrations in combination dredging and LMB treatments exceeded the Dutch standard 10-fold. Total zooplankton abundance, and particularly Cladocera, increased in all enclosures over the course of the experiment. The limited effect of LMB in the enclosure experiment and the violation of the Dutch La standard when combined with dredging disqualify LMB as an intervention agent in the restoration of the pond.</p

Notitie KIWK: maatregeleffectiviteit plasherstel : Algenrespons op mosselfilter in de Linievijver

Een van de doelen van de Kennisimpuls waterkwaliteit (KIWK) is het kwantificeren van de effectiviteit van lokale maatregelen in verschillende watertypen op verschillende organismengroepen. In dit document wordt de effectiviteit van een mosselfilter op de algenrespons in de Linievijver geanalyseerd. Op basis van de chlorofyl-α en nutriënten concentraties en het aandeel blauwalgen (Cyanophyta) in de fytoplanktonmonsters kan worden geconcludeerd dat er een tijdelijke vermindering in eutrofiering was tijdens de periode (2014-2016) waarin het mosselfilter werkzaam was. De analyse van de fytoplanktongemeenschap laat een verdeling in drie groepen over de tijd zien, waarbij er ook verschillen zijn tussen verschillende jaren dat het mosselfilter niet actief was. Door het verschil in de fytoplanktongemeenschap voor en nadat het mosselfilteractief, komt de verbetering niet goed naar voren in de trendanalyse met de Principal Response Curve methode. Fytoplankton heeft echter een zeer korte levensduur waardoor algenbloei zeer variabel kan zijn over tijd. Zeer frequente metingen van (blauwalgen) chlorofyl-α concentraties geven mogelijk efficiënter inzicht in de maat van algen bloeien en daarmee eutrofiëring over tijd dan moment opnames van de fytoplanktongemeenschap in plassen en meren. Een nadeel is echter dat met het gebruik van chlorofyl-α concentraties niet naar het effect van eutrofiëring op hogere planten, andere algen (benthisch) en dieren gekeken wordt. Deze andere organismen kunnen tevens als indicator dienen voor langere termijn processen, waarvoor fytoplankton minder geschikt is

Management of eutrophication in Lake De Kuil (The Netherlands) using combined flocculant – Lanthanum modified bentonite treatment

Abstract Eutrophication of Lake De Kuil (The Netherlands, 6.7 ha, maximum depth 9 m) has frequently caused cyanobacterial blooms resulting in swimming bans or the issue of water quality warnings during summer. The eutrophication was mainly driven by sediment phosphorus (P)-release. The external P-loading was in the range of the critical loading for phytoplankton blooms. Hence, the reduction of the internal P-loading provided a promising way to reduce cyanobacterial blooms. To mitigate the cyanobacterial blooms, the combination of a low dose flocculant (iron(III)chloride; Flock) and a solid phase phosphate fixative (lanthanum modified bentonite; Lock) was applied in May 2009. This combined approach both removed cyanobacterial biomass from the water column and also intercepted P released from the bottom sediments. Immediately after treatment, the Secchi depth increased from 1.5 m up to 5 m. Sediment P-release decreased from 5.2 mg P m−2 d−1 (2009) to 0.4 mg P m−2 d−1 (2010) but increased in later years. Mean summer concentrations of total P decreased from 0.05 mg L−1 (1992–2008) to 0.02 mg L−1 (2009–2014) and chlorophyll-a from 16 μg L−1 (1992–2008) to 6 μg L−1 (2009–2014). Mean summer Secchi depth increased from 2.31 m (1992–2008) to 3.12 m (2009–2014). The coverage of macrophytes tripled from 2009 to 2011. In the winter of 2010/2011 Planktothrix rubescens bloomed, but cyanobacterial biomass decreased during the summers after the Flock and Lock treatment in comparison to prior years. After the Flock & Lock the bathing water requirements have been fulfilled for six consecutive summers. As the sediment P-release has gradually increased in recent years, there is a risk of a reversion from the present mesotrophic state to a eutrophic state

Notitie KIWK: maatregeleffectiviteit plasherstel : Algenrespons op nutriënten-reductie in de Kleine Melanen

Een van de doelen van de Kennisimpuls waterkwaliteit (KIWK) is het kwantificeren van de effectiviteit van lokale maatregelen in verschillende watertypen op verschillende organismengroepen. In dit document wordt de effectiviteit van een pakket van nutriënt reducerende maatregelen op de algenrespons in de Kleine Melanen geanalyseerd. Er kan worden geconcludeerd dat zowel de eerste ingrepen (2010-2012) als ook de afronding van het volledige maatregelenpakket waarbij de bron is aangepakt (april 2018) tot een duidelijk zichtbare reductie van de P-concentratie en chlorofyl-α concentraties hebben geleid. Er is ook een reductie in de concentratie blauwalgencellen (Cyanophyta) en groenalgencellen (Chlorophyta) in 2019. Op basis van de relatieve abundantie van de fytoplanktongemeenschap lijkt voornamelijk een verdeling te ontstaan tussen de jaren vóór en ná het nemen van de eerste maatregelen. De verlaging van de tolerantie voor totaal P van de indicatoren in de monsters genomen na 2014 behalve 2016 duidt op een vermindering in de eutrofiering van de Kleine Melanen. De tweedeling van de clusters voor het nemen van de maatregelen komen echter niet goed naar voren in de trendanalyse met de Principal Response Curve methode. Fytoplankton heeft echter een zeer korte levensduur waardoor algenbloei zeer variabel kan zijn over tijd. Zeer frequente metingen van (blauwalgen) chlorofyl-α concentraties geven mogelijk efficiënter inzicht in de maat van algen bloeien en daarmee eutrofiëring over tijd dan moment opnames van de fytoplanktongemeenschap in plassen en meren. Een nadeel is echter dat met het gebruik van chlorofyl-α concentraties niet naar het effect van eutrofiëring op hogere planten, andere algen (benthisch) en dieren gekeken wordt. Deze andere organismen kunnen tevens als indicator dienen voor langere termijn processen, waarvoor fytoplankton minder geschikt is

Blauwalgen duurzaam verdwenen na watersysteemherstel in de Groote Melanen

Om blauwalgenoverlast te bestrijden is in de Groote Melanen bij Bergen op Zoom in 2015-2016 eensamenhangend pakket verbetermaatregelen uitgevoerd, gebaseerd op een watersysteemanalyse.De maatregelen richtten zich op het verminderen van de externe en interne nutriëntenbelasting enhet realiseren van helder water met waterplanten. Na uitvoering van het maatregelenpakket is dewaterkwaliteit sterk verbeterd en is blauwalgenoverlast duurzaam bestreden. Het ecosysteemontwikkelt zich in de gewenste richting. De resultaten tonen de kracht van deze aanpak op basis vaneen diagnose