Chemical Pre-Treatment of Sewage - A Cost-Benefit Method
373
being investigated in laboratory experiments; the findings are evaluated and
presented, not forgetting the possible disadvantages.
2
Treated Sewage Reuse in Hungary
Although a water shortage occurs frequently, primarily in the late summer and
early autumn period, in several regions of Hungary, the present reuse of treated
sewage is not significant.
In the 1960s, 1970s, and 1980s, the National Water Authority financed
different research works concerning the use of treated municipal sewage for
irrigation of industrial plants, or plants not for direct human or food industry uses.
In the Great Hungarian Plain, where water shortage occurs periodically, some of
the state farms and huge cooperatives sponsored field experiments. The health
authorities examined the effect of irrigation. The results demonstrated that the
plants contained no harmful matters that could originate from treated sewage.
The most remarkable practical application of wastewater reuse in Hungary is
the irrigation of a poplar plantation with pretreated (primary settling, sewage
pond, activated sludge) wastewater. The first plant of this type was built in Gyula
in 1969, receiving municipal sewage of the town mixed with biologically treated
sewage of food industry wastewater (Vermes 1985, 1996). Several other irrigation
plants have been constructed with capacities ranging from 40-10 000 m 3 dai l
(Marczisak et al. 2000); however, their application has been significantly reduced
in the last 10 years due to the lack of interest.
Plants operated with the above technologies have been studied at several places
in Hungary. The two main aspects during these surveys were the efficiency of
wastewater treatment (with special regard to nutrient removal) and the effect of
wastewater treatment on the quality of the soil and surface and groundwaters.
The measurements showed that the poplar irrigation resulted in efficient
nutrient removal from the wastewater and significant tree production (Vermes
1985, 1996; Marczisak et al. 2000). However, results have also demonstrated that
pretreatment was not sufficient, consequently pollution of the soil and
groundwater was possible at irrigation sites built without a drainage system.
The research works and field experiments basically finished at the beginning of
1990s, when social-economical change started in Hungary. At that period, the
different state-owned research funds had been reduced significantly, and a great
number of large state farms and cooperatives had collapsed. The small private
farms are not interested in irrigation; so treated sewage reuse is not applied in
Hungary.
Water shortage occurs in the northeast of the Great Hungarian Plain in the
southern part of the region situated between Rivers Danube and Tisza. Subsurface
water is used for water supply (deep confined aquifer) and irrigation of small
gardens (shallow groundwater). The treated sewage has been driven into different
subsurface recipients, so that finally the wastewaters of this region reach the Black
Sea. This means that the regional water sources are decreasing continuously. The
373
being investigated in laboratory experiments; the findings are evaluated and
presented, not forgetting the possible disadvantages.
2
Treated Sewage Reuse in Hungary
Although a water shortage occurs frequently, primarily in the late summer and
early autumn period, in several regions of Hungary, the present reuse of treated
sewage is not significant.
In the 1960s, 1970s, and 1980s, the National Water Authority financed
different research works concerning the use of treated municipal sewage for
irrigation of industrial plants, or plants not for direct human or food industry uses.
In the Great Hungarian Plain, where water shortage occurs periodically, some of
the state farms and huge cooperatives sponsored field experiments. The health
authorities examined the effect of irrigation. The results demonstrated that the
plants contained no harmful matters that could originate from treated sewage.
The most remarkable practical application of wastewater reuse in Hungary is
the irrigation of a poplar plantation with pretreated (primary settling, sewage
pond, activated sludge) wastewater. The first plant of this type was built in Gyula
in 1969, receiving municipal sewage of the town mixed with biologically treated
sewage of food industry wastewater (Vermes 1985, 1996). Several other irrigation
plants have been constructed with capacities ranging from 40-10 000 m 3 dai l
(Marczisak et al. 2000); however, their application has been significantly reduced
in the last 10 years due to the lack of interest.
Plants operated with the above technologies have been studied at several places
in Hungary. The two main aspects during these surveys were the efficiency of
wastewater treatment (with special regard to nutrient removal) and the effect of
wastewater treatment on the quality of the soil and surface and groundwaters.
The measurements showed that the poplar irrigation resulted in efficient
nutrient removal from the wastewater and significant tree production (Vermes
1985, 1996; Marczisak et al. 2000). However, results have also demonstrated that
pretreatment was not sufficient, consequently pollution of the soil and
groundwater was possible at irrigation sites built without a drainage system.
The research works and field experiments basically finished at the beginning of
1990s, when social-economical change started in Hungary. At that period, the
different state-owned research funds had been reduced significantly, and a great
number of large state farms and cooperatives had collapsed. The small private
farms are not interested in irrigation; so treated sewage reuse is not applied in
Hungary.
Water shortage occurs in the northeast of the Great Hungarian Plain in the
southern part of the region situated between Rivers Danube and Tisza. Subsurface
water is used for water supply (deep confined aquifer) and irrigation of small
gardens (shallow groundwater). The treated sewage has been driven into different
subsurface recipients, so that finally the wastewaters of this region reach the Black
Sea. This means that the regional water sources are decreasing continuously. The