Barriers against cyanotoxins in drinking water< zurück

Objectives:

TOXIC was subdivided in to 4 main sections, raw water quality (1), analysis (2), treatment strategies (3), and cost evaluation and exploitation (4).

(1): The objectives of raw water quality focus on the sampling and analysis of raw water used for drinking water treatment, contaminated with cyanobacteria and cyanotoxins. The collation and dissemination of the data form the basis for developing an early warning system for toxic cyanobacterial bloom.

(2): The section analysis focuses on: a) supplying the partners with purified microcystins, anatoxin-a and cylindrospermopsin, and extracts containing these cyanobacterial toxins b) writing and distributing standard operating procedures (SOPs) for toxin extraction, clean-up and analyses by chromatographic, immunological and enzymatic methods c) providing analytical training and consultation, and d) organising a two-phase intercalibration exercise concerning microcystin analysis in water samples by solid-phase extraction followed by high-performance liquid chromatography with diode-array detection.

(3): The treatment strategies focus on conventional treatment (flocculation/rapid filtration), polishing treatment (oxidative steps and activated carbon), final treatment (disinfection), and alternative trains (dissolved air flotation and membrane filtration).

Cost effective approaches based on computer simulation models of algal toxin removal are developed by lab-scale-, pilot scale as well as full scale experiments.

(4): An essential tool of exploitation is the practical guidance to water utilities. This guidance considers the following aspects: selection, design and operation of water treatment processes to achieve cost-effective removal of algae and cyanotoxins for particular situations, and the implementation of secure and cost-effective monitoring strategies for cyanotoxins for operational purposes.

Scientific achievements:

(1): Waterbody monitoring schedules were maintained by all partners. Sampling is carried out according to current standard operating procedures applied by all WP 2 partners, with additional molecular methods being used by University of Dundee. The data-reporting system and the database of all TOXIC partners are established and published under www.cyanobacteria-platform.com. The raw water monitoring techniques are assessed under the aspect of early warning. In conclusion a list of early warning techniques is designed.

(2): The analytical work of TOXIC-partners was supported by: a) preparation and delivery of several tens of milligrams of cyanotoxins to the partner laboratories b) generation of final SOPs c) organisation and reporting of several intercalibration exercises which show that different laboratories can reach excellent results if using the SOP´s. The output of sub-projects 1 and 2 was the Analytical Manual “Cyanobacterial Monitoring and Cyanotoxin Analysis”.

(3): Complex water treatment trains are considered in lab-, pilot- and full-scale. The treatment screening test is a tool for indication of induced toxin release The toxin threshold concentration is defined by Maximum Tolerable (MT)-values of cyanobacteria in raw waters.

The removal of dissolved cyanobacteria is examined by polishing (oxidative- and/or adsorptive) - and alternative treatment trains. The disinfection (chlorine, chlorine dioxide, chloramines, UV irradiation) of treated water is defined as final treatment.

A complete data set for describing the kinetics of the chemical oxidation of MC-LR, Anatoxin-a and Cylindrospermopsin with ozone, chlorine, chlorine dioxide, permanganate and chloramines has been produced.. The data set has been expanded to include impact of NOM dissolved in water.

The kinetic results obtained allow the establishment of operational conditions for waterworks to assess their optimum oxidation and disinfection regimes to deal with cyanobacterial pollution.

For optimization of activated carbon equilibrium and isotherm tests were used. Rapid Small Scale Column Tests (RSSCT) have also been used to obtain the design parameters of the large scale water treatment systems, i.e.: EBCT, filter dimension and GAC lifetime. Protocols for rapid GAC- test and BAC- filtration were designed.

The Laboratory work is accompanied by full scale monitoring in end-user waterworks. All results are summarizes in the ANNEX chapter of TOXIC.

Final models have been developed to simulate the performance of oxidants and granular activated carbon (GAC) for removal of algal toxins during water treatment. A detailed model has been developed for ozonation. A less complex model has been developed for other oxidants (chlorine, chloramine, chlorine dioxide and potassium permanganate),

(4) Practical advice will be provided through a Best Practice Guidance Manual, and stand-alone software packages for process selection, design and operation. The latter will allow a range of treatment schemes to be assessed and costs estimated, in order to identify cost-effective options for specific sites. The guidance manual is addressed to: RAW WATER MANAGEMENT AND MONITORING - WATER TREATMENT PROCESS DESIGN AND OPERATION FOR CYANOTOXIN REMOVAL - TREATMENT RISK MANAGEMENT AND MINIMIZATION - PROCESS SELECTION. The Manual “Best Practice Guidance for Management of Cyanotoxins in Water Supplies” is available in a final form.

A list of APPENDICES provide generic information for toxin analysis and monitoring under the aspects of early warning, water treatment technologies and a review of performance for cyanotoxin removal, and laboratory test procedures to assist in process selection, design and operation.

Socio-economic relevance and policy implications:

TOXIC includes: the development of tools for better water body control (drinking water reservoirs and recreational waters), the evaluation of analytical procedures for the target toxins, and the systematic optimization of the water treatment processes for cyanotoxin removal/ destruction. The TOXIC activities are of high interest to national agencies, water utilities, as well as transboundary operating water companies. The dissemination of TOXIC is based on intensive contacts to 10 water authorities, 9 water companies, several national environmental protection agencies and health authorities.

Conclusions:

The partners agreed that TOXIC was a very successful joint research project. The results of the project show, that removal of cyanobacteria toxins - cell bound and dissolved - in drinking water treatment trains is possible with high efficiency if the following aspects are considered:

- raw water management and early warning systems

- application of precise and optimized analytical techniques

- optimized treatment trains.

The results of TOXIC deliver all this information in the form of:

- Analytical Manual: “Cyanobacterial Monitoring and Cyanotoxin Analysis”

- Technical Manual: “Best Practice Guidance for Management of Cyanotoxins in Water Supplies” and

- Final Report of TOXIC including the ANNEX

An excellent basis for further research in the field of algal toxins is provided by TOXIC outputs.