FURTHER DEVELOPMENT AND OPTIMISATION OF A PILOT-SCALE STRAW BASED BANKSIDE FERMENTER FOR CONTROL OF ALGAL GROWTH
Report No FR0327

H A James

Oct 1992

SUMMARY

I BENEFITS

The growth of blue-green algae in raw water storage reservoirs may present problems in terms of drinking water supply and the recreational use of these water bodies. Methods of controlling algal growth (to minimise such problems) need to be investigated in order to ascertain their potential, and to establish the problems associated with their practical application.

II OBJECTIVES

III REASONS

It has previously been shown (FWR Report FR0285) that decomposing barley straw controls the growth of the blue-green alga Microcystis aeruginosa. However there is a need to establish an acceptable way of dosing larger water bodies, such as water storage reservoirs, with the algistatic factor produced by decomposing straw. A preliminary feasibility study demonstrated that a bankside fermenter could, in principle, provide a suitable dosing method.

IV CONCLUSIONS

A continuous circulation fermenter has been constructed and successfully used to control the growth of the blue-green alga Microcystis aeruginosa. However, several problems which suggest that it is not a good model for a field scale system have been identified. It is therefore essential to deploy a flow-through system in the field.

V RECOMMENDATIONS

A field based flow-through fermenter system needs to be set up so that its performance can be assessed.

VI RESUME OF CONTENTS

Laboratory scale experiments have demonstrated that the principle of a fermenter for dosing the algistatic agent produced by decomposing straw shows practical promise. The mechanism of the inhibition of growth in green algae appears to be different to that in blue-green algae, and that the two algal types are susceptible to different components of the straw liquor. Regular straw replacement seems to be necessary for continued blue-green algal control.

Approaches have been made to Thames Water, Yorkshire Water and British Waterways for possible sites to test a field scale fermenter. One site (Earlswood reservoir, south of Birmingham) owned by British Waterways appears promising and is currently under investigation.

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