DD278573A1 - METHOD AND DEVICE FOR CLEANING HIGH-LOADED WASTEWATER BY ANDEROBE FERMENTATION - Google Patents

Abstract

The invention relates to a method for anarobic cleaning highly polluted wastewater with biogas production. The object of the invention is to realize a reliable process design and a high degree of degradation with low residual load in the cleaning of highly polluted wastewater. The goal is achieved by the polluted wastewater is flowed through a floor reactor from bottom to top and thereby repeatedly contacted with active biomass, the sedimentation of the microorganism coagulum is used. Screen plates are installed in the reactor. There is a biofiltration of the wastewater, the degree of purification is adjustable by the number of floors.

Description

! Field of application of the invention

The invention relates to a process for the anaerobic treatment of wastewater with the simultaneous production of biogas from j unwanted ingredients. The invention belongs to the field of wastewater treatment and can be used for cleaning

highly polluted wastewater, in particular from animal production plants.

Characteristic of the known technical solutions

After the known technical solutions of the purification of wastewater such as liquid manure, the solids are removed before j biological treatment by means of mechanical separation units. The liquid separating component is then passed through

Aeration by means of activated sludge process microbiologically treated. The two-stage process with one high and one low-load stage as well as one-stage processes with extended aeration times are used. In both process operators, in addition to the separated manure solid, a purified, almost sulfur-free and reduced in nutrient content liquid manure. Disadvantage of these methods are the considerable electrical energy required to operate the ventilation units and large amounts of excess sludge, which occur in addition to the purified liquid manure. In an aerobic stabilization of this excess sludge, as described in DD 216501, a further considerable amount of electrical energy is necessary, since at high sludge loads up to one third of the raw waste is obtained as excess sludge. These disadvantages are avoided when using anaerobic cleaning methods. In the practical operation of anaerobic slurry cleaning, the classic stirred tank reactor is state of the art. However, with the use of ideally mixed reactor processes, long residence times are required due to the slow growth rate of microorganisms involved in degradation of the ingredients. The required for this ι large-volume biogas reactors require a high investment cost.

The long generation times, especially of the methanogenic bacteria, are circumvented by microorganism immobilization techniques, that is, such processes are becoming increasingly important. In this case, filler particles are usually introduced into the biogas reactors which serve as colonization surfaces for the microorganisms (DD 218608, US Pat. No. 4,568,464, US Pat. No. 4,482,456, AT 363871, CH 645081, DE 2930812).

According to DE 3032869, the wastewater is passed through carriers, with macroporous substances having a low specific weight (organic polymer compounds) being used as carrier material.

Such plastic carriers are used in numerous processes (inter alia IP 60-150895, IP 60-143897), but also mineral-based carriers are used (inter alia IP 60-132697). For the reliable design of these methods, a flow rate must be sought for the liquid, which excludes blockages of the filter during long-term operation. At the same time short-circuit currents must be avoided.

In the process according to DE 2924465, the waste water is subjected to an anaerobic treatment from the bottom to the top through a bacterial sand fluidized bed. For these fluidized bed processes, energy must be used to keep the fluidized bed in suspension.

In the floating layer reactor according to DE 3046686 float particles of resin, clay or activated carbon in a rising from bottom to top wastewater stream. A combination of anaerobic filter and floating layer reactor represents the device according to US 4561974, wherein the wastewater passes through a layer filter.

In the process of DE 3043160, the reactor contains a backmixed bed of methanogenic bacteria, the reactor being run as an anaerobic cycle filter. For a high degradation but a complicated monitoring system is necessary, the contact of the wastewater with the microorganisms must be repeated several times by a circulating stream.

Object of the invention

The object of the invention is to realize a reliable process design and a high degree of degradation with low residual load in the purification of highly polluted wastewater and to make the process adaptable to the respective degree of contamination of the wastewater.

Explanation of the essence of the invention

The object of the invention is to convert the organic substances present in the waste water largely to biogas with a high rate of biogas formation. According to the invention, this object is achieved in that the contaminated wastewater is repeatedly contacted with active biomass in a functionally reliable operation design. For this purpose both the Koagulationsvrfrhalten methanogenic bacterial cultures and the sedimentation of the coagulum are used technically. The wastewater is metered into a vertical reactor at the bottom of the reactor. In the reactor there are at least 3 levels in the form of screen plates, whose hole diameter is 0.4 to 0.8 mm. The microorganisms are deposited on these screen plates. The added wastewater flows through the reactor from bottom to top and is thus repeatedly filtered biologically. The desired degree of cleaning can be controlled via the number of levels.

In solving the problem, known elements of anaerobic fermentation technology are already being modified and further developed from wastewater treatment in such a way that a substantially more optimal process design results. The main idea of the invention is to realize a high degradation rate at high biogas formation rate and reliable process design.

In the process according to the invention, the decomposition of the organic constituents takes place by means of a material guide which is adapted to the specificity of the wastewater and works in a functionally reliable manner, in particular under high load. The number of floors and thus the biological filtration performance can be extended as desired

 The fermentation process is characterized by:

- a temperature of 24 ° C to 40 ° C

- a pH between 6.5 and 8.5

- A residence time for the wastewater of 3 hours to 2 days.

The main advantages of the process over currently used methods of wastewater treatment are:

- Increasing the rate of biogas formation and thus the degradation performance by treatment in several floors - • Extensive discharge of the waste water from polluting ingredients by gradual cleaning

- Reliable process design through a failure-prone material management

embodiment

As part of the process example manure is used from an industrial pig farm. The liquid manure is separated from solids by known process combination sedimentation / centrifugation (filtration). The solids are utilized as valuable organic fertilizer

 The liquid phase can be characterized by the following material properties.

TS 9.8 kg / m ³ OTS 6.1 kg / m ³ C _FS 5.8 kg / m ³

BOD ₅ 8.1 kg / m ³ CSV ₀ , 9.1 kg / m ³

The liquid manure is heated by heat exchange so that the fermentation takes place at a temperature of 35 ° C and a pH of 8.0. B ^ it .ier average residence time of 10 hours was c * e biogas formation rate increased to more than 10 m ³ / m ³ · d. In a fermentation in 4 days, the reduction in BOD _{5 is} 95% and in CSV 90%. The methane content in biogas is 80%.

Claims (2)

Invention claim: 1. A process for the purification of highly polluted wastewater by anaerobic fermentation with biomass retention, characterized in that the preheated wastewater a ! horizontal floor reactor continuously flows from bottom to top, while in 3 to 10 levels are contacted with the organic constituents degrading biomass that the Degradation of polluting substances on the number of floors is controllable, that the average j hydraulic residence time 3 hours to 2 days and that the organic ingredients j are largely converted into a biogas with a surprisingly high methane content of 80%, ί whereby 80% and more of the CSV and 90% of the BOD _{6 are} degraded, 2. Apparatus for carrying out the method according to claims. 1, which is made of a horizontal ! Biogas reactor with a height / diameter ratio of 3: 1, characterized by j that in 3 to 10 levels horizontal screen plates with a hole diameter of 0.4 to 0.8 mm are installed on which the microorganisms in the reactor settle and which are continuously flowed through from bottom to top by the wastewater.