372
I. Licsko et al.
The drinking water consumption has decreased significantly since the
beginning of the 1990s, parallel to the social-economic changes in Hungary. Due
to this, the wastewater flow entering the wastewater-treatment plants has also been
reduced. As the quantity of the pollutants in the domestic sewage has not changed,
the pollutant concentration of the sewage has increased. Consequently, at the
sewage treatment plants, which were already hydraulically overloaded previously,
a new problem arises: the difficulties of lower wastewater flows and higher
pollutant concentrations, while the pollutant loads have not changed significantly.
The answers to the questions raised by the new problem have not been found
successfully in many cases. At a few sewage treatment plants - where it was
possible - according to the wastewater flow decrease, the operators reduced the
volume of reactor basins, neglecting the changed pollutant concentrations. This
solution has certainly reduced the costs of operation; however, the efficiency of
pollutant removal has decreased. Therefore, optimization of the process
performance is needed to concur with the changed circumstances.
The existing Hungarian standard concerning the quality of discharged treated
sewage into surface recipient controls the plant nutrient (P and N) concentrations
in the case of lakes and reservoirs only. Considering that Hungary belongs to the
River Danube water catchment area, effective nutrient removal should be
performed in the near future.
At the beginning of the new century, Hungary faces several problems
concerning construction and operation of sewage-treatment plants. It is necessary
to find relatively low-cost solutions, because in Hungary the drinking water fee
and sewage charge are high, compared to the personal income. The most
important problems and tasks to be solved are as follows:
Upgrading the existing WWTPs and solving the operation problems caused by
sewage volume reduction while the pollutant loads have not changed.
Building new sewage-treatment plants with relatively high pollutant removal
efficiency at low capital and OMR costs.
Increasing the nutrient removal efficiency at the existing (mainly originally
high-loaded) sewage treatment plants to use cost-effective methods.
Chemical methods are used widely in drinking water treatment if the source is
surface water. Furthermore, the most effective method for phosphorus removal,
applied since the mid 1960s in sewage treatment, is chemical treatment.
Chemical treatment can be used in different ways in wastewater treatment: as
the only treatment process (primary precipitation or direct precipitation) or in
combination with biological treatment processes (pre-, simultaneous, or postprecipitation).
The aim of this chapter is to find a cost-effective method to be applied in
sewage treatment, which increases the organic and nutrient removal efficiency of
existing treatment plants.
Considering that a significant part of the organic pollutants in the sewage is
connected to suspended solids (including colloid particles), increasing their
removal efficiency in the primary settling tank results in low (organic) pollutant
load in the activated sludge processes. Based on these facts, the advantages of
chemical pretreatment of sewages at different wastewater-treatment plants are
I. Licsko et al.
The drinking water consumption has decreased significantly since the
beginning of the 1990s, parallel to the social-economic changes in Hungary. Due
to this, the wastewater flow entering the wastewater-treatment plants has also been
reduced. As the quantity of the pollutants in the domestic sewage has not changed,
the pollutant concentration of the sewage has increased. Consequently, at the
sewage treatment plants, which were already hydraulically overloaded previously,
a new problem arises: the difficulties of lower wastewater flows and higher
pollutant concentrations, while the pollutant loads have not changed significantly.
The answers to the questions raised by the new problem have not been found
successfully in many cases. At a few sewage treatment plants - where it was
possible - according to the wastewater flow decrease, the operators reduced the
volume of reactor basins, neglecting the changed pollutant concentrations. This
solution has certainly reduced the costs of operation; however, the efficiency of
pollutant removal has decreased. Therefore, optimization of the process
performance is needed to concur with the changed circumstances.
The existing Hungarian standard concerning the quality of discharged treated
sewage into surface recipient controls the plant nutrient (P and N) concentrations
in the case of lakes and reservoirs only. Considering that Hungary belongs to the
River Danube water catchment area, effective nutrient removal should be
performed in the near future.
At the beginning of the new century, Hungary faces several problems
concerning construction and operation of sewage-treatment plants. It is necessary
to find relatively low-cost solutions, because in Hungary the drinking water fee
and sewage charge are high, compared to the personal income. The most
important problems and tasks to be solved are as follows:
Upgrading the existing WWTPs and solving the operation problems caused by
sewage volume reduction while the pollutant loads have not changed.
Building new sewage-treatment plants with relatively high pollutant removal
efficiency at low capital and OMR costs.
Increasing the nutrient removal efficiency at the existing (mainly originally
high-loaded) sewage treatment plants to use cost-effective methods.
Chemical methods are used widely in drinking water treatment if the source is
surface water. Furthermore, the most effective method for phosphorus removal,
applied since the mid 1960s in sewage treatment, is chemical treatment.
Chemical treatment can be used in different ways in wastewater treatment: as
the only treatment process (primary precipitation or direct precipitation) or in
combination with biological treatment processes (pre-, simultaneous, or postprecipitation).
The aim of this chapter is to find a cost-effective method to be applied in
sewage treatment, which increases the organic and nutrient removal efficiency of
existing treatment plants.
Considering that a significant part of the organic pollutants in the sewage is
connected to suspended solids (including colloid particles), increasing their
removal efficiency in the primary settling tank results in low (organic) pollutant
load in the activated sludge processes. Based on these facts, the advantages of
chemical pretreatment of sewages at different wastewater-treatment plants are