Occurrence and elimination of cyanobacterial toxins in drinking water treatment plants

Toxin-producing cyanobacteria (blue-green algae) are abundant in surface waters used as drinking water resources. The toxicity of one group of these toxins, the microcystins, and their presence in surface waters used for drinking water production has prompted the World Health Organization (WHO) to publish a provisional guideline value of 1.0 mug microcystin (MC)-LR/l drinking water. To verify the efficiency of two different water treatment systems with respect to reduction of cyanobacterial toxins, the concentrations of MC in water samples from surface waters and their associated water treatment plants in Switzerland and Germany were investigated. Toxin concentrations in samples from drinking water treatment plants ranged from below 1.0 microg MC-LR equiv./l to more than 8.0 microg/l in raw water and were distinctly below 1.0 microg/l after treatment. In addition, data to the worldwide occurrence of cyanobacteria in raw and final water of water works and the corresponding guidelines for cyanobacterial toxins in drinking water worldwide are summarized.     

Sustainable production of organic acids via ozonation of biomass derived 5-hydroxymethylfurfural and furfural

Extracting value-added chemicals from renewable resources has attracted much attention in facing the crises arising from fossil resources. This study elucidates a promising strategy of producing valuable organic acids, including maleic acid, formic acid and succinic acid, via a new ozonation process. 5-hydroxymethylfurfural (HMF) and furfural, two platform chemicals obtained from biomass hydrolysis, are used as the raw materials. Under alkaline reaction condition (25 °C, 10 mg/L O₃, and 90 min), improved yields of maleic acid, succinic acid and formic acid reached 25.3 wt%, 10.0 wt% and 41.1 wt% from HMF, as well as 17.6 wt%, 2.5 wt% and 79.5 wt% from furfural; respectively. This sustainable manufacturing technology exhibited significant advantages, including one simple process, room condition, avoiding of organic solvent and absence of metal catalysts. This work paves the ways from biomass to commercial organic acids via hydrolysis followed by ozonation.     

Control of bromate and THM precursors using ozonation combined system

Objective To investigate the feasibility of reducing THM precursors and controlling bromate taste and odor in drinking water taken from the Yellow River by an ozonation combined system. Methods The appropriate ozone dosage was determined, and then the changes of TOC, UV254 and THM formation potential (THMFP) in the combined system were evaluated. Results One mg/L ozone could effectively remove taste and odor and meet the maximum allowable bromate level in drinking water. The pre-ozonation increased THMFP, but the conventional treatment system could effectively reduce the odor. The bio-ceramic filter could partly reduce CHCl3FP, but sometimes might increase CHCl2BrFP and CHClBr2FP. The biological activated carbon (BAC) filter could effectively reduce CHCl3FP and CHCl2BrFP, but increase CHClBr2FP. Compared with other filters, the fresh activated carbon (FAC) filter performed better in reducing THMFP and even reduced CHClBr2FP. Conclusion The combined system can effectively reduce taste, odor, CHCl3FP, and CHCl2BrFP and also bring bromate under control.