Einfluß algenbürtiger organischer Substanzen auf Flockung und Filtration

Abstract

Summary:The treatment of water from eutrophic lakes is disturbed by extensive development of plankton, which is caused by particulate algogenic organic substances and frequently also by dissolved ones. They are released by excretion, diffusion, cell destruction, separation of cell wall substances and metabolic processes in the course of the cellular reproduction in dependence on the physiological state of the algae. At a sufficient dosage of metallic salts as a flocculant, the extracellular organic substance (EOS) may act as an anionic flocculation aid in the concentration range of 1 ... 2 mg/l C. There is decisive the mass ratio: Me (metal as flocculant)/EOS (as TOC).Below a mass ratio Fe : TOC=2 ... 3 the EOS disturbs the process of flocculation and filtration. l a c k u n g s h i l f s m i t t e l z u s a t z schwach k a t i o n i s c h k a t i o n i s c hFa hr weiseO F a n ? - -t C h l o r e l l a18 Acta Iiydrocllinl., Bd. Hieraus lassen sich folgende Schliisse ableiten :-Die EOS aus der hochmolekularen Fraktion stort den Flockungs-und FlockenabtrennprozeB starker als die EOS der niedermolekulnren Fraktion. -Bei den Grun-und Blaualgen stort der hochmolekolare Anteil der EOS mit zunehmendem Kulturalter starker.-Besonders aosgeprkgt sind storende Eigenschaften der EOS der spatstationaren Wachstumsphasen der Blaualge Psewlanabaena, der G r k a l g e Dicfyosphaerium sowie der Kieselalgen Xelosira und Achnnnthes.-Von den niedermolekularen Substmzen weist nur die EOS der logarithmischen Wachstumsphase der Kieselalge Fragilaria ein ebenso stark storendes Verhalten auf.-Ein Zusammenhang des Storeffektes der EOS mit den verschiedenen Algenklassen ist nicht vorhanden. Be.stimmung der Ladunqs~onzentrationDie Restinimiiiig der Ladungsdichte von Partikeln bzw. der Ladungskonzeiitratioii einer Wasserprobe erfolgt durch Zugabe eiiies entgegengesetzt geladenen Polymers oder Polyelektrolyten bis zur Ladungsneut ralisation. Zur Bestimmung der negativen Ladungskonzentration der im Wasser gelosteii EOS wird eiii kat,ionischer PolyActs hydrochiin. hydrobiol. 17 (1989) 3 251 Tiibellr fi. EC)S-Konxeiitr;ition~ri (rng/l TOC), die r.rfnrtlerlicth sind, uni cine St.ornng d e~ Plockungsprozcsws auszulijscn, dargrst.cllt durch die Erhohung der Kcsttriibung im Filt.rat (von en. 0,25 m-l n i i f 0.5 in -1 ) (Versurlie mit. der ,.kleinen" Flocb-nngstestapparstur) (1989) s t a t i o n a r e PhaseAbh. 9. Abhangigkeit des Zusntzes a n Pe-LII-

The impact of zeta potential changes on Ceratium hirundinella cell removal and the ability of cells to restore its natural surface charge during drinking water purification

“…However, the subsequent increasing Ca(OH) 2 concentrations showed an increasing ZP trend, but it remained below the proposed ZP range required for good coagulation conditions. Increased pH levels (>pH 9.70) were recorded for the lowest organic polymer concentration which can be an ascribed to the low constant Ca(OH) 2 ) treatment without low Ca(OH) 2 concentration (10 mg L À1 ) caused no pH adjustments, since pH levels remained similar to the control (Fig. 1a).…”

“…1a). When dosing Ca(OH) 2 in combination with SiO 2 , the lowest Ca(OH) 2 concentration of 60 mg L À1 caused the initial ZP to decrease ( Fig. 1b; from À13.38 mV to À16.71 mV).…”

“…1 2 organic polymer and organic polymer. The ZP range proposed by Sharp et al 28 required for good coagulation (À10 mV to +3 mV) is indicated by the dotted line in Fig.…”

“…The ZP analyser with a built-in calibrated pH meter was used to analyse the ZP and pH of the cells and the filtered source water. The coagulant concentration of 10 mg L À1 Ca(OH) 2 and 10 mg L À1 organic polymer achieved the best coagulation conditions as assessed against an operation ZP window of between À10 mV to +3 mV. This Ca(OH) 2 and organic polymer dosing concentration was used to purify water with increasing cell concentrations (2000 cells per mL to 7000 cells per mL, increments of 1000) applying settling times of 20 minutes, 120 minutes and 240 minutes.…”

“…31 This investigation focuses specically on the use of Ca(OH) 2 and a cationic organic polymer that will be dosed simultaneously and separately as part of the treatment options (as a primary coagulant or coagulant aid) to investigate the inuence of ZP on the coagulation conditions of the freshwater dinoagellate, C. hirundinella.…”