200-100,000 m3/day INSTALLATIONS AND WORKS
For tertiary treatment of municipal sewage we have elaborated a new biochemical purification technology with simultaneous removal of carbon-nitrogen compounds (patent No. 2114070).
After mechanical treatment, the initial sewage is driven to first step purification CW mixing chamber 1. Impurities oxidation is done at maximum loads on the biomass and high speed of cellular synthesis. Permitted is residual impurity of the settled water after the CW, its BOD value between 30 and 70 mg/L. Further on, the water is directed to second step purification CW mixing chamber 2, i.e. the nitrifier.
In case of low initial concentrations of ammonium nitrogen, some part of the initial sewage may be driven to the CW2 mixing chamber, and biomass from CW1 to adjust the nitrifying sludge concentration.
To accelerate propagation of nitrifying microorganisms and control the nitrification process, helium-neon lasers (HNL) are installed above the chutes of the irrigating system. As the sludge mixture is exposed to radiation in the nitrifier, the growing speed of the ammonifying bacteria rises 1.5 times. The water is driven from CW2 to mixer 3 installed before denitrifier 4. Flake-like substrate from the reactor is also driven to the mixer in order to prepare organic substrate 5. The reactor is meant to mix some part of the initial sewage with the additional sludge from CW1. With the aim of intensive propagation of sludge microorganisms and acceleration of the impurities sorption, the liquid is exposed to radiation by HNL. The water from the mixer containing substrate flakes is driven to denitrifier where it is filtered through the layer of suspended and immobilised denitrifying sludge. Plastic sheets having holes and bristles are used as a feed and filter.
To make the sludge mixture circulate, it is recommended to use axial-flow and single-unit pumps of 8-10 m water column lift and 360-960 r.p.m.
To catch the waste and sand we recommend to use (for the CWs not exceeding 1,000 m3/day) network containers with a solid bottom; for the CWs not exceeding 1,000 - 3,000 m3/day - bow sieves; for the CWs not exceeding 100,000 m3/day - gradated fine purification grills of 2 mm mesh manufactured by the RIOTEK Company (St. Petersburg), as well as vertical sandcatchers.
A possibility of people's contamination during their contact with waste water and air at wastewater treatment plants speaks of the necessity of complete automation of the purification process. Minimum mechanical equipment used at the installations and works of our Research Institute, reliability and simplicity of control permit to solve this problem. Meanwhile, the new equipment controlling the purification processes is to meet the following additional requirements:
- sensing devices and nitri-denitrification process controls should be included in the software package;
- the CW house should have gas-analysers and ventilation adjusting equipment;
- CW circulation pumps should be provided with equipment regulating the number of revolutions in case of any change in the sewage inflow and composition. This will permit to optimise the control flow, reduce the possible heat loss at a cold season and cut the power consumption in case of temporary reduction in the sewage quantity and composition.
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We are in search of partners for joint implementation of the above technology.
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