Martin Pivokonsky

The impact of algogenic organic matter on water treatment plant operation and water quality: A review

ABSTRACT The proliferation of algal and cyanobacterial blooms globally has led to renewed interest in understanding the impact of cell populations on water treatment plant (WTP) performance and the resultant water quality, particularly the role of algogenic organic matter (AOM). This review discusses current knowledge on the composition of AOM, how it interferes with water treatment process technologies applied for the treatment of algal blooms, and how it affects water quality. Specifically, it was shown that AOM can lead to increased coagulant demand, increased propensity of membrane fouling, and contribute to disinfection by-products (DBPs). Identified knowledge gaps included a need for further research on the impact of cellular organic matter (COM) after an algal bloom collapses and the impact of interactions between AOM and natural organic matter (NOM).

Adsorption of cellular peptides of Microcystis aeruginosa and two herbicides onto activated carbon: effect of surface charge and interactions.

In this research, the adsorption of two herbicides, alachlor (ALA) and terbuthylazine (TBA), on granular activated carbon (GAC) in the presence of well-characterized peptide fraction of cellular organic matter (COM) produced by cyanobacterium Microcystis aeruginosa was studied. Two commercially available GACs were characterized using nitrogen gas adsorption and surface charge titrations. The COM peptides of molecular weight (MW) < 10 kDa were isolated and characterized using MW fractionation technique and high-performance size exclusion chromatography (HPSEC). The effect of surface charge on the adsorption of COM peptides was studied by means of equilibrium adsorption experiments at pH 5 and pH 8.5. Electrostatic interactions and hydrogen bonding proved to be important mechanisms of COM peptides adsorption. The adsorption of ALA and TBA on granular activated carbon preloaded with COM peptides was influenced by solution pH. The reduction in adsorption was significantly greater at pH 5 compared to pH 8.5, which corresponded to the increased adsorption of COM peptides at pH 5. The majority of the competition between COM peptides and both herbicides was attributed to low molecular weight COM peptides with MW of 700, 900, 1300 and 1700 Da.

Optimized Reaction Conditions for Removal of Cellular Organic Matter of Microcystis aeruginosa During the Destabilization and Aggregation Process Using Ferric Sulfate in Water Purification

The efficiency of removal of cellular organic matter (COM) of cyanobacteria Microcystis aeruginosa from water with ferric sulfate is influenced primarily by coagulant dosage and reaction pH. Therefore, optimization of the reaction conditions is a prerequisite for efficient purification of surface waters. Because the isoelectric point of COM occurs at a low pH, the purification of waters containing this organic matter should take place in an acidic pH range. It was also found that proteins are removed more efficiently than other organic substances (mainly polysaccharides).

Optimization of NOM Removal during Water Treatment

Abstract The aim of this paper is to describe the removal efficiency of individual fractions of natural organic matter (NOM) and the aluminum transformation during treatment of two types of surface water with an increased concentration of NOM of various origins. The coagulation conditions (dose of destabilization reagent and reaction pH value) were optimized for the best NOM and aluminum removal. The results show that the NOM removal efficiency depends on the NOM character, using destabilizing reagents and reaction conditions. The optimized doses of destabilization reagents influence especially the removal of hydrophilic charged (CHA) and very hydrophobic acids (VHA) fractions during treatment of both types of raw water. In contrast to this, the removal of hydrophilic neutral (NEU) fraction is very low (ϕ NEU =0.13–0.22). The optimal destabilization reagent dosage is characterized by the lowest content of the total reactive aluminum concentration and relatively low concentration of dissolved organic aluminum.

The effect of global velocity gradient on the character and filterability of aggregates formed during the coagulation/flocculation process

This paper describes the influence of the global velocity gradient G on the properties of aggregates formed during the coagulation/flocculation process. The methods of image and fractal analysis were used to determine aggregate size and structure, respectively. The influence of these aggregate properties on separation using depth filtration is also described. Experiments were conducted in a pilot plant operation. The suspension was formed in a flow mixing tank with global velocity gradients ranging from 28.4–307.2 s−1 and ferric sulphate used as a coagulant. Filtration velocities were 3 and 6 m h−1. Predictably, it was shown that the aggregate size decreased with increasing global velocity gradient G. Furthermore it was demonstrated that, with increasing G, the aggregates became more compact and regular (the D2 fractal dimension increased) and the suspension became more homogeneous in size. The aggregates with the smallest diameter and highest D2 fractal dimension displayed the best filterability, i.e. penetrated throughout the full depth of the filter bed and generated a minimum pressure drop.

Occurrence of microplastics in raw and treated drinking water

The study investigates the content of microplastic particles in freshwater and drinking water. Specifically, three water treatment plants (WTPs) supplied by different kinds of water bodies were selected and their raw and treated water was analysed for microplastics (MPs). Microplastics were found in all water samples and their average abundance ranged from 1473 ± 34 to 3605 ± 497 particles L-1 in raw water and from 338 ± 76 to 628 ± 28 particles L-1 in treated water, depending on the WTP. This study is one of very few that determine microplastics down to the size of 1 μm, while MPs smaller than 10 μm were the most plentiful in both raw and treated water samples, accounting for up to 95%. Further, MPs were divided into three categories according to their shape. Fragments clearly prevailed at two of the WTPs and fibres together with fragments predominated at one case. Despite 12 different materials forming the microplastics being identified, the majority of the MPs (>70%) comprised of PET (polyethylene terephthalate), PP (polypropylene) and PE (polyethylene). This study contributes to fill the knowledge gap in the field of emerging microplastic pollution of drinking water and water sources, which is of concern due to the potential exposure of microplastics to humans.

Investigating the coagulation of non-proteinaceous algal organic matter: Optimizing coagulation performance and identification of removal mechanisms

The removal of algal organic matter (AOM) is a growing concern for the water treatment industry worldwide. The current study investigates coagulation of non-proteinaceous AOM (AOM after protein separation), which has been minimally explored compared with proteinaceous fractions. Jar tests with either aluminum sulphate (alum) or polyaluminium chloride (PACl) were performed at doses of 0.2-3.0 mg Al per 1 mg of dissolved organic carbon in the pH range 3.0-10.5. Additionally, non-proteinaceous matter was characterized in terms of charge, molecular weight and carbohydrate content to assess the treatability of its different fractions. Results showed that only up to 25% of non-proteinaceous AOM can be removed by coagulation under optimized conditions. The optimal coagulation pH (6.6-8.0 for alum and 7.5-9.0 for PACl) and low surface charge of the removed fraction indicated that the prevailing coagulation mechanism was adsorption of non-proteinaceous matter onto aluminum hydroxide precipitates. The lowest residual Al concentrations were achieved in very narrow pH ranges, especially in the case of PACl. High-molecular weight saccharide-like organics were amenable to coagulation compared to low-molecular weight (<3 kDa) substances. Their high content in non-proteinaceous matter (about 67%) was the reason for its low removal. Comparison with our previous studies implies that proteinaceous and non-proteinaceous matter is coagulated under different conditions due to the employment of diverse coagulation mechanisms. The study suggests that further research should focus on the removal of low-molecular weight AOM, reluctant to coagulate, with other treatment processes to minimize its detrimental effect on water safety.

Physicochemical approach to alkaline flocculation of Chlorella vulgaris induced by calcium phosphate precipitates

Alkaline flocculation has been studied due to its potential as a low-cost harvesting method for microalgae. However, surface properties (zeta potential, contact angles) as inputs into physicochemical interaction models have not yet been applied systematically. In this work, forced alkaline flocculation of the freshwater microalgae Chlorella vulgaris induced by calcium phosphate precipitates was studied as a model system. Response surface methodology was used to quantify the effect of independent variables (concentration of Ca2+ (0.5-0.5 mM) and PO43- (0.05-0.35 mM), pH (8-12) and ionic strength (1-19 mM)) on the zeta potential (ZP) of microalgae, and the turbidity (T) of inorganic precipitates. Flocculation tests and their modified versions were carried out. The flocculation efficiencies obtained were interpreted with respect to predictions of physicochemical interaction models. It was found that flocculation was possible under conditions where appropriate precipitates were formed in the presence of cells. Under these conditions, flocculation of negatively charged Chlorella vulgaris was induced not only by positively charged, but also by negatively charged calcium phosphate precipitates at an early phase of nucleation. The driving force for interactions between oppositely charged cells and precipitate particles was electrostatic attraction, while the attraction between equally charged entities may have resulted from a negative total balance of apolar (Lifsitz-van der Waals) and polar (acid-base) interactions. Medium components did not interfere with flocculation, while cellular organic matter decreased flocculation efficiency only to a very limited extent.

A fluidized layer of granular material used for the separation of particulate impurities in drinking water treatment

A fluidized layer of granular material used for the separation of particulate impurities in drinking water treatment This paper deals with the application of a fluidized layer of granular material (FLGM) for the direct separation of destabilized impurities during drinking water treatment. Further, it investigates the effect of operation parameters (fluidized layer grain size, technological arrangement, velocity gradient, retention time, dosage of destabilisation reagent and temperature) on the aggregation and separation efficiency of the layer. The tests were carried out in a pilot plant scale. Aluminium sulphate was used as the destabilisation reagent. The highest separation efficiencies were achieved, when the particles entered the fluidized layer immediately after the dosing of the destabilisation reagent, when they had the lowest degree of aggregation. The separation efficiency (φ) also increased with increasing velocity gradient and the maximal value was reached at the velocity gradient of about 250 s-1. The most efficient separation of aluminium was achieved at 5 °C, but the effect of temperature on the efficiency of organic matter separation (φTOC) was not very significant. The maximal efficiency of separation on the layer grains reached the values φAl = 0.81 at the optimal dosage DAl = 1.55 mg L-1 and φTOC = 0.31 at the optimal dosage DAl = 2.36 mg L-1. The indisputable advantage of using FLGM for the separation of impurities is that they are intercepted on the layer grains in a form of solid, water-free shell (or coat) with the density of 2450 kg m-3, and there is no need to deal with the sludge dewatering. Využití fluidní vrstvy zrnitého materiálu pro separaci nečistot při úpravě vody Příspěvek se zabývá využitím fluidní vrstvy zrnitého materiálu (FLGM) pro přímou separaci destabilizovaných nečistot při úpravě vody a vlivem provozních parametrů (velikost zrn náplně, technologické uspořádání, gradient rychlosti, doba zdržení, dávka destabilizačního činidla, teplota) na agregační a separační účinnost vrstvy. Testy byly prováděny na poloprovozním modelu fluidní vrstvy. Jako destabilizační činidlo byl použit síran hlinitý. Nejvyšší separační účinnosti byly dosahovány, pokud částice nečistot vstupovaly do fluidní vrstvy bezprostředně po nadávkování destabilizačního činidla, kdy byl jejich stupeň agregace nejnižší. Separační účinnost (φ) se také zvyšovala s narůstající hodnotou gradientu rychlosti ve fluidní vrstvě a maximální hodnoty dosáhla při gradientu kolem 250 s-1. Hliník byl nejúčinněji separován při nízké teplotě (5 °C), nicméně na účinnost separace organických látek (φTOC) teplota příliš velký vliv neměla. Maximální účinnost separace na zrnech fluidní vrstvy dosáhla hodnot φAl = 0,81 při optimální dávce DAl = 1,55 mg L-1 a φTOC = 0,31 při optimální dávce DAl = 2,36 mg L-1. Nespornou výhodou využití fluidní vrstvy jako separačního prvku je skutečnost, že nečistoty jsou na zrnech FLGM zachycovány ve formě pevné skořápky (hustota 2450 kg m-3), která neobsahuje kapalnou vodu, a kal tudíž nemusí být odvodňován.

A Method for Evaluation of Suspension Quality Easy Applicable To Practice: The Effect of Mixing on Floc Properties

A Method for Evaluation of Suspension Quality Easy Applicable To Practice: The Effect of Mixing on Floc Properties The paper introduces the test of aggregation as a simple, inexpensive method of evaluating suspension quality during drinking water treatment, suitable for use in both laboratory and operation conditions. The procedure and derivation of the aggregation test is described. The method is used for a demonstration of the influence of mean velocity gradient and mixing time on floc properties formed during the aggregation in a Couette reactor. It was proved that with increasing velocity gradient, the size of the aggregates present in the suspension decreases, and the suspension is substantially more homogeneous than with use of lower gradients. Further, it was confirmed that the size of aggregates reaches the steady state after a specific mixing time, which becomes shorter with increasing value of velocity gradient. Metoda Hodnocení Kvality Suspenze Snadno PouŽItelná V Praxi: VLIV Míchání NA Vlastnosti Vloček. Příspěvek představuje test agregace jako jednoduchou a levnou metodu stanovení kvality suspenze při úpravě vody vhodnou pro použití v laboratorních i provozních podmínkách. Je popsán metodický postup i odvození testu agregace. Metoda je použita pro hodnocení vlivu středního gradientu rychlosti a doby míchání na vlastnosti vytvářených agregátů (vloček) při agregaci v Couettově reaktoru. Bylo prokázáno, že se vzrůstajícím gradientem se snižuje velikost agregátů přítomných v suspenzi a suspenze je značně více homogenní než při použití nízkých gradientů rychlosti. Dále bylo potvrzeno, že velikost agregátů dosahuje po určité době míchání stabilní hodnoty. Čas pro dosažení tohoto ustáleného stavu se zkracuje s rostoucí hodnotou použitého gradientu.