374
1. Licsko et al.
reuse of treated sewage can be an effective method to slow this unfavorable
tendency.
The appropriate treatment of sewage needs more efficient pollutant removal
than simple reuse for irrigation. The treated sewage, recharged into the soil,
should not contain phosphorus and nitrogen compounds, while these were the
most important components of treated sewage for irrigation. Chemical
pretreatment, biological treatment - upgrading with nitrogen removal - sand
filtration and using the membrane technology (ultrafiltration or nanofiltration)
could provide an acceptable water quality for groundwater recharge.
The investment and operational and maintenance costs of this technology are
extremely high at this time in Hungary. At present, there are no organizations,
local governments, state-owned or private companies which would finance this
technology. The water shortage is not so serious; today only water management
presents problems. A very low level of treated sewage reuse is predicted in
Hungary for this decade.
3 Background
The very first experiments on chemical wastewater treatment were carried out
in 1740, in Paris. By 1890 there were more than 200 wastewater treatment plants
in England applying lime or different ferric salts for chemical treatment. Later,
these plants were converted to biological treatment plants (Morrissey and
Harleman 1990).
Morrissey and Harleman (1990) mentioned early initiations for chemical
pretreatment introduced by Rudolfs in 1929 where efficient settling of wastewater
was achieved on applying ferric chloride. By the 1930s, several plants were in
operation in the USA, where different chemicals were added into settling tanks to
improve the settleability of solids (Morrissey and Harleman 1990). However, this
method fell into disfavor when compared to biological treatment because the large
concentrations of metal salts produced large quantities of sludge (Morrissey and
Harleman 1992).
In the developed countries by the end of the 1960s different methods known
from the chemical industry (colloid destabilization, adsorption, stripping,
coagulation, etc.) began to be applied after biological wastewater treatment. These
methods gained the name tertiary treatment at the third IA WPRC conference in
1970, in San Francisco.
The application of physicochemical methods as tertiary treatment of wastewater
had been studied already in the late 1960s and 1970s. In spite of several trials,
tertiary treatment of wastewater has not spread on a broad scale in the past 30
years. Basically, only chemical phosphorus removal has been being applied
extensively. This is due to the fact that phosphorus precipitation by using different
chemicals satisfies real requirements, giving a high efficiency of phosphorus
removal at a reasonable cost.
1. Licsko et al.
reuse of treated sewage can be an effective method to slow this unfavorable
tendency.
The appropriate treatment of sewage needs more efficient pollutant removal
than simple reuse for irrigation. The treated sewage, recharged into the soil,
should not contain phosphorus and nitrogen compounds, while these were the
most important components of treated sewage for irrigation. Chemical
pretreatment, biological treatment - upgrading with nitrogen removal - sand
filtration and using the membrane technology (ultrafiltration or nanofiltration)
could provide an acceptable water quality for groundwater recharge.
The investment and operational and maintenance costs of this technology are
extremely high at this time in Hungary. At present, there are no organizations,
local governments, state-owned or private companies which would finance this
technology. The water shortage is not so serious; today only water management
presents problems. A very low level of treated sewage reuse is predicted in
Hungary for this decade.
3 Background
The very first experiments on chemical wastewater treatment were carried out
in 1740, in Paris. By 1890 there were more than 200 wastewater treatment plants
in England applying lime or different ferric salts for chemical treatment. Later,
these plants were converted to biological treatment plants (Morrissey and
Harleman 1990).
Morrissey and Harleman (1990) mentioned early initiations for chemical
pretreatment introduced by Rudolfs in 1929 where efficient settling of wastewater
was achieved on applying ferric chloride. By the 1930s, several plants were in
operation in the USA, where different chemicals were added into settling tanks to
improve the settleability of solids (Morrissey and Harleman 1990). However, this
method fell into disfavor when compared to biological treatment because the large
concentrations of metal salts produced large quantities of sludge (Morrissey and
Harleman 1992).
In the developed countries by the end of the 1960s different methods known
from the chemical industry (colloid destabilization, adsorption, stripping,
coagulation, etc.) began to be applied after biological wastewater treatment. These
methods gained the name tertiary treatment at the third IA WPRC conference in
1970, in San Francisco.
The application of physicochemical methods as tertiary treatment of wastewater
had been studied already in the late 1960s and 1970s. In spite of several trials,
tertiary treatment of wastewater has not spread on a broad scale in the past 30
years. Basically, only chemical phosphorus removal has been being applied
extensively. This is due to the fact that phosphorus precipitation by using different
chemicals satisfies real requirements, giving a high efficiency of phosphorus
removal at a reasonable cost.