The purpose of the Biodestil technology is treatment of a wide range of industrial effluent, with special emphasis placed on landfill leachate. The standard system is comprised of the following components:
Influent Tank
Leachate is delivered to the influent tank through a piping system. This tank is equipped with a pH measurement system. At this point, reactive compounds, metered according to the quantity and type of waste water are added to it, in order to optimize the efficiency of the process of evaporation. The additives are metered automatically. If it is required for a particular type of waste water, it can be screened before entering the evaporator.
Heating System
The choice of waste water heating method depends on the existing equipment of the facility (landfill) and on access to cheap sources of energy, or other local conditions. An optimum solution is to use the heat from cooling of existing equipment (for example electric power generators).
The heating system generates heating liquid (hot water) required to reach the boiling temperature of waste water.
If it is not possible to use waste heat, a boiler can be installed to obtain adequate waste water temperature. Flammable gases, produced in the boiler during combustion of fuel, are used to obtain adequate temperature of the heating liquid.
Any fuel can be used for this purpose, first of all solid fuel, with the option to incinerate some types of biomass, such as sawdust and wood waste. Conventional fuel can also be used, including coal, fuel oil and natural gas. Gases generated during combustion are emitted through the stack after cleaning in a cyclone, if the fuel used requires reduction of emitted particulate. The boiler is shielded with refractory bricks. Combustion takes place in a closed chamber, using primary and secondary air.
This technology features higher energy efficiency in comparison with conventional boilers, as well as improved emission parameters and longer life of the equipment. Additionally, boiler installation does not require any additional structures which would result in design modification and cause interference with the boilers’ operating mode. The heating liquid circulates in a closed hydraulic system from the boiler to the evaporator. Circulation is provided by a centrifugal pump designed to work with a high-temperature liquid. The closed heating liquid system is protected against pressure surges by an overflow tank, which is also used for replenishing the liquid volume.
The evaporation and condensation system
Correct evaporation can significantly reduce the volume and load of contaminants, and also break up the toxic compounds present in waste water, which have a negative impact on biological treatment. The system is comprised of the following pieces of equipment:
Steam separator
Steam separator is the evaporator section where waste water reaches the boiling point and is separated into the gaseous and liquid phase. Steam passes to the condenser, and the remaining waste, which cannot be evaporated, is collected at the bottom of the separator. The waste is removed when it reaches adequate density. Density (hydration) of waste can be freely adjusted.
Heat exchanger
A special heat exchanger designed for the waste water to reach adequate temperature.
Level control
The level control keeps waste water in the evaporator on the right level, allowing correct evaporation. When the evaporator level is different from the preset optimum value, the level control automatically closes or opens the flow of waste water into the tank.
Condenser
The condenser's task is to recover heat and completely condense the steam. Completely treated process water is used by the condenser as the cooling liquid.
Vacuum pump and condensate flow pump
Vacuum pump and condensate flow pump. Because boiling takes place under conditions of operating pressure lower than the atmospheric pressure, wastewater boils at a temperature below 100°C (approx. 70ºC). This way the evaporation process uses less energy and fuel in comparison with evaporation at atmospheric pressure. Negative pressure is obtained with a vacuum pump with a liquid ring. The condensate is pumped from the condenser with an adequate centrifugal pump.
Cooling System
In the cooling system the coolant (water) causes cooling and condensation of steam generated by the evaporator in the condenser. The cooling liquid circulates in a closed system, from the accumulation tank, through the cooling tower to the evaporator. Water cooled in the cooling tower flows down in a stream of air generated by electrically propelled fans. A large part of water evaporates and is merged with the air stream as water vapor. The energy required for evaporation is obtained by reducing the temperature of water flowing to the bottom without evaporation. Cold water from the bottom of the cooler is then used as the cooling liquid in the condenser. Water losses due to evaporation occur in the cooling tower. Shortage of water is supplemented from completely treated waste water or from the water supply system.
Stripping and scrubber system
The STRIPPING/SCRUBBER process is used when the final content of ammonium nitrogen in the infiltration water to be treated exceeds the acceptable limits for treated water.
Stripping – condensed water is pumped to the top part of the chamber and falls in the direction opposite to the air stream direction. The process removes ammonia and other volatile contamination from water, and transfers them to the air stream. Before the system is put into operation, depending on the measurement results a reactive compound is added to facilitate ammonia stripping.
The scrubber performs a reverse process, which consists in absorbing ammonia and other stripped compounds into the water stream. An acidic reactive compound is added to the water stream in order to intercept ammonia and increase its concentration. Air blown out from the scrubber is sucked into the fan of the stripping system, therefore the process is closed and does not result in emissions and in unpleasant odors.
Biological treatment system
Water obtained in the condenser does not contain any substances which are not biodegradable. It contains only the most volatile compounds, which were evaporated. The composition of these compounds is simple and they are easily biodegradable. A centrifugal pump delivers them to the biological reactor. The purpose of the biological reactor is to obtain output parameters of treated water required for public waters.
Matching of the pH hardness to the right value for the biological reactor may require adequate pH adjustment.
Basic reactions taking place during biological treatment:
- Synthesis: it consists in absorption and inclusion of simple nutritional substrates in the cytoplasm of microorganisms and development of new molecules. During synthesis, organic matter is used as a source of energy for growing new microorganisms.
- Oxidation reaction, or accelerated degradation and stabilization reaction: it consists in oxidation of the cell's own cytoplasm by microorganisms, at a time when there is no organic matter for use as food. During oxidation, the substrates used subsequently in the synthesis process are released. Part of the cytoplasm is converted into water and carbon dioxide, by which the volume of microorganisms is reduced.
The biological reactor is designed in such a way that it retains water until total biodegradation of pollutants in waste water is achieved. A blower system supplies oxygen in an amount corresponding with the oxygen demand and the reactor size.