Liquid purification or separation – Processes – Treatment by living organism
Patent
1996-07-19
1998-06-16
McCarthy, Neil
Liquid purification or separation
Processes
Treatment by living organism
210624, 210626, 210630, 210631, 210663, 210903, 210906, 210912, C02F 330, C02F 142
Patent
active
057664765
DESCRIPTION:
BRIEF SUMMARY
Our invention refers to a method for cleaning contaminated domestic and industrial effluent water streams with the active sludge method and by the introduction of innovative processes for treating the ammoniate and phosphate contents of such streams and for the promotion of the activation of biological culture. The methods achieves a high degree of purification at a rapid rate. It results in obtaining recycle water of a high purity, using low installation and operating cost equipment.
The activated sludge method for cleaning contaminated water has a very wide range of applications and is often simply referred to as the method for biological treatment of contaminated water. It employs a tank for primary settling, an aeration tank and a tank for secondary settling. In the course of its development, multi-stage systems have been introduced, where two- or three- stage aeration is conducted. The two- stage aeration method is combined with the development of conditions for the growth of bacteria only in the primary settling tank and for the growth of higher micro-organisms (such as protozoa and other) in the secondary settling tank. This has also required the adjustment of the residence times in the to tanks. Furthermore, multi-stage systems for the treatment of ammoniates and phosphates present in the contaminated water stream have been developed.
The process of biological treatment of contaminated water with the activated sludge method is characterised by the residence times in high rate processes and low rate processes. The high rate process, with a residence time of 2.5 hours appears to favour the growth of bacteria principally, whereas the low rate process favours the growth of a variety of micro-organisms where bacteria and protozoa are the principal constituents, depending on the residence times, usually being in the range of 4 to 6 hours. The high rate process has a small oxygen consumption and maintains a small concentration of a biological culture in the order of 500 kg./liter. It responds positively to a rise in temperature up to 45.degree. C., achieves high degrees of purification, up to 70%, and requires a small consumption of energy. The low rate process, however, does not benefit from rising the temperature above 20.degree. C., operates in an excess biological culture concentration of 3000 kg/ litter and has high operating costs associated with it.
It is also known that in warm-climate regions, the sewage or industrial waste end-up in aeration tanks where temperatures in excess of 30.degree. C. prevail. Thus, air solubility in such tanks is limited. The saturation oxygen content at 15 Celsius is 10.4 kg/lit, whereas this drops to 6.6 kg/lit at 35 Celsius. Thus, extended aeration installations tend to underperform in such regions.
It is derived from the analysis above that the method for contaminated water purification by the activated sludge method is not effectively studied nor optimised as yet. Among functionality problems associated with it, one could list: contaminated water stream rises. toxicity, in the form of organic toxic matter and heavy toxic metals, to a higher or lesser degree, the approach is rather of theoretical importance development of the biological culture and the rate of the biological treatment, thus leading to serious economic and environmental drawbacks.
Taking into account the above mentioned advantageous and disadvantageous aspects of the biological treatment of contaminated water with the activated sludge method, the inventors have invented, researched and operated pilot solutions which manage to handle all these aspects successfully and highly beneficially.
BRIEF DESCRIPTION OF THE DRAWING
A pilot plan diagram of the instant invention.
The inventors have proved that the process of biological treatment of contaminated water with the method of the activated sludge can be optimally operated in a two-stage aeration process in a process, where the first stage operates in a non-acidic environment with removal of nitrates and acting as a toxicity trap. According to this sol
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Valkanas George N.
Vlyssides Apostolos G.
Green Theodore M.
Innoval Management Limited
McCarthy Neil
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