Algal Organic Matter (AOM) is released into the water environment as extracellular organic matter (EOM) resulting from the metabolic processes of living algal/cyanobacterial cells, or as cellular organic matter (COM), which is a mixture of compounds originating from the lysis and decomposition of phytoplankton cells. AOM comprises a whole range of organic substances, primarily high-molecular weight biopolymers such as proteins and polysaccharides, but also peptides, amino-acids, oligosaccharides, fats, fatty acids, nucleic acids, amino-sugars, lipopolysaccharides, aldehydes and others. During water treatment, AOM are removed together with other impurities (e.g. humic matter, clay particles and algal/cyanobacterial cells) by the process of coagulation, which lies in the dosing of coagulants (most frequently aluminium or ferric salts) into raw water and their interaction with the mentioned impurities. A floc suspension is formed through mixing from the originally dissolved or colloidal substances and coagulants, which can be removed by sedimentation, flotation and/or filtration. Coagulation efficiency varies for different substances and it is influenced by the dose/type of coagulant and pH value. Coagulation efficiency can be increased by oxidation (using potassium permanganate, ozone, chlorine, UV radiation in combination with chlorine or hydrogen peroxide) preceding the coagulation itself (i.e. pre-oxidation). AOM poses a problem because it contains substances causing disagreeable odour, toxic substances (cyanobacterial toxins) and after water chlorination it can produce toxic disinfection by-products (DBPs). Therefore, there is a need for their maximum removal. AOM removal is more difficult than the removal of whole cells. It was found that unlike cells that can be removed with more than 90% efficiency, the removal efficiency of AOM-proteins by coagulation is 70 – 80 %, and non-protein AOM is removed from less than 25%. Therefore, our research is aimed at the optimization of coagulation and pre-oxidation processes to reach the maximum AOM removal and at the description of interaction mechanisms involved in coagulation and pre-oxidation of AOM.
- Characterisation of AOM (Algal Organic Matter) composition and structure and description of their properties significant from the perspective of coagulation (portion of proteins and polysaccharides, molecular weight analysis, surface charge characteristics, quantity of functional groups)
- Description of interaction mechanisms between AOM and coagulants
- Selection of conditions (dose and type of coagulant, pH value) suitable for reaching the maximum efficiency of AOM coagulation
- Influence of AOM oxidation with different oxidants (potassium permanganate, ozone, chlorine, UV-Cl, UV-Cl/H2O2) on the subsequent coagulation – selection of suitable oxidation conditions, oxidant selection, description of the effect of oxidation on AOM structure, evaluation of the oxidation effect on AOM toxicity
- Research on the effect of AOM on coagulation/flocculation of other impurities present in raw water (humic matter, clay particles, algal/cyanobacterial cells) and description of their mutual interaction mechanisms
- Study of the effect of AOM on properties of formed aggregates (flocs made of AOM and coagulant)
- Innovations of water treatment technology with respect to the character of AOM present in raw water