TECHNICALLY SPEAKING
In addition, SMART Units can reach an aeration
Performance of Korean HYBACS plants during proving trials
efficiency of up to 7kg O2/kWh. Since they
remove up to 50% of the load from the Treatment works
Unit Flow rate Av. BOD Av. TN Av. TP
wastewater, they bring about a substantial power
Busan Mun Cess
m
3
/day 3412 - - -
saving for the downstream aeration. A further
influent mg/1
- 3059 589 99
power saving is made because less mechanical
effluent
mixing is needed in the smaller reactors, giving a
mg/1 - 27 8 2.0
reduction in the overall power consumption by
removal
% - 99.0 98.6 97.9
HYBACS of at least 40%.
GeumSung Mun
m
3
/day 200
The rotor speed can be automatically adjusted
influent
mg/1 - 171 26.3 1.3
to control the DO concentration of the liquor,
effluent
allowing performance to be manipulated
mg/1 - 6.0 2.8 0.3
depending on treatment need. When operated
removal
% - 96.4 88.3 55.2
at comparatively high DO concentrations,
TongBok Mun
m
3
/day 45000 - - -
ammonia removal and nitrogen removal are
influent
mg/1 - 145 39.8 5.1
favoured and, when operated at comparatively
low DO concentrations, phosphorus removal is
effluent
mg/1 - 8.1 10.5 0.9
favoured. Intermediate concentrations give
removal
% - 94.4 73.6 80.8
removal of all three nutrients.
Since SMART Units can be added to process can biologically remove a TP load of the 22 million customers that Aqualia serves
conventional AS plants, these can be converted equivalent to a minimum of 3% of the BOD in Spain and other countries.
to BNR, even when not nitrifying. load in the wastewater, which is sufficient to Ammonia and TN was removed at Coleshill
reduce the TP concentration of the treated during a 10-week run from June to August, when
South Korea effluent to less than the local standard of 2 mg/l the SMART Unit was operated at a comparatively
More than 20 plants operate in South Korea (expressed as a maximum). This performance is high DO concentration. For most of the time the
treating a wide range of wastewater types. Table achieved whilst achieving an appreciable TN ammonia removal was greater than 97%, and TN
1 lists average data obtained during proving trials removal, as indicated in the table (above). removal greater than 70%, peaking during the last
of generally three months at three of these week at an average value of 93%. Currently,
plants treating municipal sewage. Even though European pilot plants simultaneous removal of NH4-N, TN and TP is
HYBACS can treat raw or settled sewage, all three As part of the BwB initiative to expand HYBACS being optimised through proactive DO control,
plants treat unsettled wastewater, which is application beyond Korea, two major water and steady state performance will be attained in
common practice in South Korea, as is the companies, in the UK and Spain, are a few more weeks. Initial results at Avila, where
disposal of surplus sludge to landfill sites in the collaborating to demonstrate the process at pilot the system is being run to remove TP as well as
form of dewatered raw cake. scale. In the UK, Severn Trent Water (STW) NH4-N and TN, show that during the last
The quality standard in South Korea for treated commissioned a pilot plant in February at month of operation, ammonia removal averaged
effluents from plants treating municipal sewage Coleshill Wastewater Treatment Works (WwTW) 93%, TP removal averaged 79% and TN
from urban drainage systems is expressed in near Birmingham, to evaluate the potential whole removal averaged 65%, but performance
terms of maxima which, for BOD, TN and TP, are life cost benefits of this process for ammonia and continues to improve.
generally 10 mg/l, 20 mg/l and 2 mg/l nutrient removal. In Spain, Aqualia started up a The COD removals at both pilot plants are
respectively. The plants at GeumSung and second pilot plant in July at Avila WwTW, some averaging about 95%, and the SS concentrations
TongBok listed in Table 1 were designed to meet 100km north-west of Madrid. Many of Spain’s of the treated effluents are generally less than 15
this standard. natural waters have been designated as sensitive mg/l, a performance only limited by the small
The Busan Plant treats municipal cess (night in terms of EU nutrient classification, requiring a scale clarification tanks. In large scale plants
soil), brought to the plant in road tankers. The wide application of BNR, which will affect many treating municipal sewage, SS concentrations of
plant reduced average BOD by 99% from 3,000 treated effluents are generally less than 10 mg/l.
mg/l in the wastewater to less than 30 mg/l in
the treated effluent. Very high removals of TN Conclusions
and TP were also obtained with residuals of less Large scale experience in densely populated
than 10 mg TN/l and biological removal of Korea has shown that the HYBACS process
phosphorus close to 98%. allows a smaller footprint compared with the
The TongBok plant is the largest municipal equivalent activated sludge system, while
plant, treating an average flow of 45,000 simultaneously leading to a power consumption
m3/day. Average BOD was typical of dilute saving of at least 40%. The demonstration of its
sewage produced in South Korea, and was BNR capability to European Standards shows
reduced to less than 10 mg/l. The full scale data how it can upgrade existing aeration plants to
shows that the process works well even for dilute deliver BNR and water quality improvement even
wastewaters but exceptionally so for strong ones. on congested sites. Given these advantages, the
In general, operational experience in municipal new process has the potential to help some
sewage treatment plants in South Korea indicates countries in their discussions with the EC on the
very good settling of the mixed liquor. Another
Many of Spain’s natural waters are designated as
removal of nutrients from wastewater, and to do
common performance characteristic is that the sensitive in terms of nutrient classification more with less. ■■■
46 Water & Wastewater Treatment November 2009
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