Liquid purification or separation – Processes – Treatment by living organism
Patent
1999-05-24
2000-10-10
Upton, Christopher
Liquid purification or separation
Processes
Treatment by living organism
210603, 210610, 210614, C02F 328, C02F 332
Patent
active
061298441
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for the treatment of waste water in a two-stage process with simultaneous recovery of energy in the form of biogas.
BACKGROUND OF THE INVENTION
For anaerobic waste water cleaning, different methods and reactors of diverse construction such as UASB, fixed bed reactors, and anaerobic activation chambers, among others, are known.
These reactors are particularly used for industrial waste waters highly loaded with organic material.
SUMMARY OF THE INVENTION
The invention is based on the objective of developing an energy-producing treatment method using anaerobic fermentation for waste water with a low load of organic materials (CSB<500 mg/l).
According to the invention, the objective is solved with a two-stage process method that consists of anaerobic treatment with the production of methane containing biogas as a first cleaning stage, and a plant clarifying unit as a second cleaning stage, where the biomass gathered in the plant clarifying unit is introduced, before the first cleaning stage, into the waste water to be treated. Beside the biomass gathered from the second cleaning stage, additional other organic or inorganic materials and wastes can be introduced into the waste water before the first cleaning step.
Through the method according to the invention, it is possible to make waste water with a low content of organic materials accessible through anaerobic methane digestion.
Before the biomass resulting from the second stage and any additional other organic or inorganic materials and waste are introduced before the first stage into the waste water, they are prepared by being crushed or pulped in a form necessary for the digestion. For the crushing and pulping of the biomass and the other wastes, methods known per se are used such as the FIMA system, ULTRA TURAX amongst others. After the intentional introduction of the biomass resulting from the second stage into the waste water before the first stage, the organic load in the waste water becomes so high that an anaerobic methane digestion is possible. Thus an energy-producing cleaning of waste water that is lightly loaded with organic materials is achieved in which an energy containing gas (combustion value 20-25 MJ/m.sup.3), which can be energetically used in numerous ways, is produced. The usual supply of oxygen, associated with energy, which is necessary for aerobic processes, can be omitted.
The quantity, to be added, of the biomass resulting from the second cleaning stage and possibly other biomasses, depends on the loading of the incoming waste water. Thus, it is possible to keep the loading of the waste water admitted to the first cleaning stage constant. The second cleaning stage is protected against overloading and there will thus be no unclarified through-flow of waste water through the second cleaning stage.
If the load in the incoming waste water is high, then the introduction of biomass from both the biomass gathered from the plant biomass in the second cleaning stage and further additional biomasses, can be completely or partially omitted. In these variants there will be a constant through-flow rate in the first cleaning stage.
Preferably, the process according to the invention will be operated so that the waste water admitted to the first cleaning stage has a load with a CSB-value of about 300 mg/l.
Likewise, it is possible to deal with a larger load in the waste water by an extended residence time in the first cleaning stage in order to reach the desired loading value of the waste water leaving the first cleaning stage.
With the process according to the invention it is possible to make use of unused plant biomass from prior art plant clarification systems in the cleaning process.
BRIEF DESCRIPTION OF THE DRAWING
The features and advantages of the invention can be better understood by reference to the following detailed description in conjunction with the accompanying drawing which is a schematic representation of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The
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