BALTIC SEAENVIRONMENT PROCEEDINGS No. 59 - Helcom

without any great difficulty. Only when it is known from
the start where tanks of what size and arrangement will be
situated is it possible to plan the necessary safety
devices and reserve capacity which will later ensure
optimum purification under all operating conditions.
Experience in Schleswig-Holstein has shown that political
programmes for the expansion of treatment plants must be
clearly formulated, otherwise the financial and technical
questions cannot be solved. There is little point in
developing programmes that are doomed to fail because of
their high cost.
What is important is that the first step leads to as high
a degree of purification as possible. This can be done by
constructing a mechanical-biological wastewater treatment
plant or one combining mechanical treatment with chemical
precipitation stages. If sufficient precipitants can be
obtained, combining mechanical treatment with chemical
precipitation can clearly reduce the amount of pollutants
discharged significantly. Only when this stage has been
introduced in most treatment plants should construction
start on equipment for nitrogen removal and biological
phosphorus removal. Even biological wastewater treatment
in combination with chemical precipitation can drastically
reduce water pollution which of course benefits the Baltic
Sea.
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