HU199754B - Process for biological purifying waste waters containing hardly decomposable compounds - Google Patents

Abstract

Biological purificn. of effluents contg. cpds. which degrade with difficulty, is carried out in the presence of at least one cyanamide formaldehyde precondensate or in the presence of organic salts formed between precondensates and organic acids.

Description

The present invention relates to an improved process for the biological treatment of wastewater containing difficult to decompose compounds.

The essence of the biological wastewater treatment processes known and applied is to subject the wastewater, where appropriate after physical and / or chemical pretreatment, to the activated sludge and to maintain the most favorable living conditions for the microorganisms forming the sludge (RG Luthy: Treatment of coal-, coking) and Coal Gasification Waste Waters, JWPCF 53, 325 (1981); WG Cousins, AB Mindler: Tertiary Treatment of Weak Ammonia Liquor, JWPCF 44, 607 (1972); PC Singer et al., Assessment of Coal Conversion Westewaters, US Dep. of Commerce, 294-338). Microorganisms decompose or convert into otherwise harmless substances pollutants that are difficult to decompose by other methods.

However, it is a disadvantage that some compounds which are susceptible to complexation and / or polymerization (e.g., cyanides, rhodanides, polyphenols, catechins, quercetin, fluorescein, aromatic polyhydroxy derivatives, pyridine bases, sulfanylamides, etc.) already at very low concentrations. the life function of the activated sludge and thus greatly reduce the efficiency of wastewater treatment. In the presence of such materials, the sedimentation ability of the bio-sludge also deteriorates.

The present invention seeks to overcome these drawbacks.

Surprisingly, our studies have found that formaldehyde precondensates of cyanamide derivatives and organic acid salts of precondensates are suitable for the inactivation of organic materials that damage biomass. Biological purification of wastewater in a biological reactor containing activated sludge in the presence of such precondensates or salts of precondensates significantly increases the efficiency of the purification. As a result of the increase in purification efficiency, the residence time of the wastewater in the biological reactor containing the activated sludge can be significantly reduced, or the treatment of a certain amount of wastewater can be carried out in a wastewater treatment plant of a much smaller size. As a further advantage, it has been found that the depleted, barely active, thus barely purifying activated sludge, by adding a small amount of formaldehyde cyanamide derivative pre-condensate or its organic acid salt, increases the purification capacity of the activated sludge abruptly and retains this cleaning capacity for a long time.

Formaldehyde cyanamide derivative condensates have already been used in wastewater treatment. No. 170,745. Hungarian Patent No. 5,123,121 discloses the separation of organic compounds containing an acidic polar group which dissociates into an anion in an aqueous medium by attaching it to two hydrophobic carbonaceous moieties, i.e. chemical wastewater treatment. According to the patent, wastewater is approached with an excess of formaldehyde cyanamide derivative, based on the amount of organic compounds, in the presence of a sulfate, phosphate or carbonate anion-providing salt in an aqueous medium. Chemical treatment of wastewater is subject to U.S. Pat. No. 1,409,460. British Patent Specification; in this case, anionic organic contaminants are also removed with the triple precondensate of formaldehyde cyanamide derivative and alkylene polyamine. This patent also discloses comparative studies where wastewater is treated with a formaldehyde cyanamide derivative precondensate and states that a very large excess of the precondensate must be added to the wastewater to be treated in order to achieve adequate purification using the latter.

A common feature of the solutions described in the cited publications is that the formaldehyde cyanamide derivative precondensate is not used in the most important biological purification process (in a biological reactor containing biological sludge for biodegradation) but in other processes of wastewater treatment. It is also common that the pre-condensate acts on the material to be removed by separating it in the form of a well-settled, easily removable precipitate. However, the effect of the formaldehyde-cyanamide derivative pre-condensate on the main process of biological wastewater treatment, ie the life functions and biodegradability of activated sludge, has not been investigated so far. In our opinion, this can be explained by the fact that one of the components of the precondensate (formaldehyde) is the most well-known cell poison, so that in the presence of the precondensate, the vital functions of the activated sludge were lost or at least significantly impaired.

However, our practical experience completely contradicts this expectation. Based on our experience that the formaldehyde cyanamide derivative precondensate is capable of regenerating depleted activated sludge, it is assumed that it is biological. during decomposition, the formaldehyde-cyanamide-derivative precondensate (unlike in previous publications) does not affect the material to be removed, but the activated sludge itself (i.e., the living material) according to a mechanism not yet discovered and adversely affects its vital functions . This recognition of us cannot be deduced from the literature, and it means overturning technical prejudices.

-2HU 199754 Β

The invention thus formed precondensate or ⁵ carried out in a known manner for biological purification of waste water containing hardly degradable compounds method of cyanamide derivative using formaldehyde precondensates of an organic acid salt. According to the invention, purification is carried out in such a way that the purification in the activated sludge biological reactor is at least 5 ppm, preferably 5 to 1 ppm by weight of waste water introduced.

100 ppm of the formaldehyde cyanamide derivative in the presence of a precondensate or an organic acid salt of the precondensate. 15

The formaldehyde cyanamide derivative precondensate can be prepared in a manner known per se. Examples of cyanamide derivatives include urea, guanidine, and the like. dicyandiamide, thiourea or melamine may be used. The precondensates ²⁰ may also be used in mixtures. Examples of organic acid salts of the pre-condensates include acetic acid salts.

Typically, the pre-condensate or the pre-condensate salt is added as an aqueous solution to the waste water to be treated. However, if desired and possible, the precondensate may be formed from the appropriate starting materials in the waste water to be treated.

The upper limit of the pre-condensate content of waste water may be the value determined by the solubility; however, such large amounts of precondensate are generally uneconomical to use. Therefore, biological purification is preferably carried out in the presence of 5 to 100 ppm of condensate or salt of precondensate, based on the amount of waste water. 40

Operational steps for biological purification - Sewerage, Aeration, Sedimentation, etc. - known by themselves.

The process according to the invention can be carried out in untreated or pre-treated wastewater by physical and / or chemical methods.

The invention is illustrated by the following non-limiting examples. 5θ

Example 1

We start from pre-treated wastewater containing the following pollutants:

phenol 1300 mg / l rhodanide 800 mg / l sulfur (in the form of thiosulphate, sulphite and sulphate) 400 mg / l cyano (free) 5 mg / l cyano (bound) 10 mg / l ammonia 200 mg / l

COD 400 mg / L

This wastewater is mixed with phosphorus nutrient salt and basified to pH 9.0 with sodium hydroxide and fed to an aeration biological reactor containing 8 g of adapted activated sludge per liter. Simultaneously with the addition of waste water, 20 mg of acetic acid salt of monomethylol biguanidine in a 5% by weight aqueous solution is added to the biological reactor per liter of waste water.

16.5 hours hydraulic residence time

Purified sewage obtained after above coal max following in quantities includes: phenol 1 mg / l thiocyanate 10 mg / L cyan (free) 0.2 mg / L cyan (knit) 1 mg / l ammonium 30 mg / L floating material no COD 300 —350 mg / L

Example 2

We start with untreated wastewater containing contaminants in broad proportions, such as catechin derivatives, quercetin, fluorescein, lipids, lipids and waxy substances.

To this wastewater, immediately before being discharged into the biological reactor, 10 mg of acetic acid salt of monomethylol biguanidine (added as an aqueous solution) is added per slurry. The mass of activated sludge in the biological reactor is 5 g per liter. After a hydraulic residence time of 24 hours, only 10% by weight of the organic contaminants in the wastewater containing the monomethylene bituanidine salt remain untreated, whereas, if purification is otherwise carried out under the same conditions but in the absence of the monomethylene biguanidine salt, 60% by weight does not decompose.

Claims (1)

A process for the biological purification of wastewater containing difficult to decompose compounds using a precondensate of formaldehyde cyanamide derivative or an organic acid salt of the precondensate, characterized in that the purification in a biological reactor containing activated sludge is at least 5 ppm —100 ppm in the presence of a formaldehyde cyanamide derivative precondensate or an organic acid salt of the precondensate.