WO2003068692A1

WO2003068692A1 - Odour-suppressors for waste-water-carrying systems

Info

Publication number: WO2003068692A1
Application number: PCT/EP2003/001163
Authority: WO
Inventors: Michael Kretzschmar
Original assignee: Ciba Specialty Chemicals Holding Inc.
Priority date: 2002-02-14
Filing date: 2003-02-06
Publication date: 2003-08-21
Also published as: AU2003206847A1

Abstract

A mixture comprising an alkali metal nitrate or alkaline earth metal nitrate and a bacteriostatically active compound, preferably an orange terpene or lime terpene, and use thereof in treating waste water.

Description

Odour-suppressors for waste-water-carrying systems

The present invention relates to a mixture comprising an alkali metal nitrate or alkaline earth metal nitrate and a bacteriostatically active compound, preferably a terpene.

Waste water is used water that is contaminated with organic and/or inorganic residues and requires purification because of its composition. Such purification is usually carried out in waste water purification plants (treatment plants).

The waste water is generally transported to the treatment plants in waste water pipes. In the case of a high organic content, unfavourable weather conditions and low water flow, and also in very long, uninterrupted pressurised pipelines, a lack of oxygen may occur, which is accompanied by a very strong unpleasant odour caused by anaerobic bacterial break-down of the organic substances in the waste water. Volatile amines and hydrogen sulfide are usually liberated in the process. Hydrogen sulfide, in particular, is very hazardous, highly corrosive for metal and concrete components, and a nuisance for those living in the vicinity of a pumping station or treatment plant.

Conventional methods of odour suppression can be divided into physical processes and chemical or biochemical processes. In the case of physical processes, waste water is, for example, vigorously agitated in the pumping station at regular intervals by means of a pump having a circulating function and is, as a result, homogenised and mixed with oxygen. It is furthermore possible to pump compressed air into the waste water pipe using a compressor, as a result of which oxygen is introduced into the air space above the water or as a result of which the water can be purged entirely.

Chemical processes usually consist of the addition of iron salts to the sulfide bond of hydrogen sulfide, of the addition of nitrate as an oxygen donor so that bacterial attack on the sulfate cannot take place (see US 3 867 284 or US 4 911 843), or of the addition of hydrogen peroxide as an oxidising agent.

Relatively recent biological processes utilise, for example, enzymatic mixtures or chemolitho- tropic bacterial cultures which oxidise hydrogen sulfide but require oxygen. US 6 309 597 describes polycyclic quinones that inhibit the activity of sulfate-reducing bacteria, as a result of which no formation of hydrogen sulfide is observed. It is furthermore indicated that the quinones can be admixed with metal nitrates and metal nitrites.

US 5 656 177 describes the use of, inter alia, orange terpene as a growth-inhibitor and slime- preventer.

JP 08 291 276 describes a mixture of starch or gelatin, an inorganic salt, for example a nitrate, of an organic acid and, optionally, a terpene.

In "Happy Household...", Vol. 35, No. 11, p. 90, the use of D-limonene as a cleaning agent or as an additive to a cleaning agent is described.

The physical methods do not, however, function satisfactorily, because they cannot prevent the cause of odour generation - the anaerobic bacterial break-down of organic substances. Although the addition of iron achieves good results, handling of the product is nevertheless critical and considerable safety precautions have to be taken. In addition, that process involves hydrogen sulfide that has already been formed. The biological processes are unreliable, too expensive and, in the case of the addition of bacteria, are based on preconditions (the presence of oxygen) which usually are not met. Only the addition of calcium nitrate is effective and not difficult to implement. However, because in that method considerable bacterial activity is generated as a result of the oxygen supplied, there is also required a considerable amount of calcium nitrate, which has to be transported in, stored and metered in.

The problem of the present invention was therefore to provide a mixture that does not have the disadvantages described above. In particular, a reduction in bacterial activity should be achieved in order to keep the requirement for added material as low as possible.

There has accordingly been found the mixture according to the invention: a) from 5 to 25 % by weight of a terpene, preferably orange terpene or lime terpene, b) from 30 to 80 % by weight of an alkali metal nitrate or alkaline earth metal nitrate, c) from 1 to 25 % by weight of an emulsifier and d) from 1 to 25 % by weight of a surfactant, the sum of the individual components being 100 % by weight.

As bacteriostatically active compound, a terpene, that is to say a monoterpene having 10 carbon atoms or also an isoprenoid having 15, 20, 25, 30 or 40 carbon atoms, is usually used, it being possible for the carbon structures to be acyclic, monocyclic, bicyclic or tricyclic. Preference is given to the C,₀H₁₆ terpene hydrocarbons, and hydrogenation and dehydrogenation derivatives thereof and also to the terpene alcohols, ketones, aldehydes and esters derived therefrom. Special preference is given to orange terpene and lime terpene.

Terpenes are generally known and also, in most cases, commercially available. Terpenes, especially orange terpene and lime terpene, generally result in inhibition of the metabolic activity of bacteria, especially those bacteria that are present in water and those that colonise the pipe skin (internal wall of the pipe), as a result of which considerably less biological break-down occurs than when those substances are not added. Associated therewith is lower oxygen consumption and less hydrogen sulfide production.

As alkali metal nitrate or alkaline earth metal nitrate there may be used sodium, potassium, magnesium or calcium nitrate, especially calcium nitrate.

Preference is given to selection of a weight ratio of nitrate to bacteriostatically active compound, especially terpene, more especially orange terpene or lime terpene, in the range from 1.5:1 to 12:1, especially from 3:1 to 6:1.

A preferred embodiment relates to a mixture comprising a) from 5 to 25 % by weight of an orange terpene or lime terpene, b) from 30 to 80 % by weight of an alkali metal nitrate or alkaline earth metal nitrate, c) from 1 to 25 % by weight of an emulsifier and d) from 1 to 25 % by weight of a surfactant, the sum of the individual components being 100 % by weight. As emulsifier, there may be used commercially available emulsifiers. Preference is given to the use of paraffin derivatives, such as alkali metal salts of paraffin sulfonate, especially the sodium salt.

As surfactant, there may usually be used commercially available surfactants. Preference is given to the use of fatty alcohols having from 8 to 30 carbon atoms or derivatives thereof, such as fatty alcohol ethoxylates, which are commercially available or obtainable by ethoxylation of fatty alcohols or mixtures thereof, or polyglycol esters or mixtures thereof.

An embodiment of the present invention relates to a method of treating waste water by adding a mixture according to the invention to the waste water being treated.

The mixture according to the invention is usually used in the form of an aqueous mixture, the water content generally being selected in the range from 1 to 50 % by weight, preferably from 15 to 30 % by weight, based on the aqueous mixture.

A further embodiment of the present invention accordingly relates to an aqueous mixture comprising the mixture according to the invention and from 1 to 50 % by weight water, based on the aqueous mixture, and to a method of treating waste water by adding to the waste water being treated an aqueous mixture comprising a mixture and from 1 to 50 % by weight water, based on the aqueous mixture, in an amount in the range from 5 to 100 ml/m³ of waste water.

The amount of the aqueous mixture according to the invention in the waste water usually depends on the length of the pipes carrying the waste water, on the flow rate and on the concentration of putrefactive substances in the waste water. Concentrations usually used are generally in the range from 5 to 100 ml/m³, especially in the range from 15 to 60 ml/m³, based on the amount of waste water.

The mixtures according to the invention have the advantage that they are miscible with water in any mixing ratio and consequently can be used in a wide range of applications. The individual components moreover act synergistically with respect to preventing odours, the surfactants penetrating underneath deposits in the conduits, thereby preventing the formation of a carpet of bacteria; the terpenes lower the bacteria's metabolism, as a result of which the foul gas production is directly reduced; and the nitrate serves as an oxygen donor, thereby preventing a lack of oxygen and also, as a result, preventing foul gas production.

Examples

Example 1 : 20 litres of waste water are taken from a municipal pumping station and divided equally between two 10-litre buckets that can be sealed shut. To one bucket there is added 0.5 ml of an aqueous mixture consisting of 60 % by weight calcium nitrate, 14 % by weight orange terpene, 5.5 % by weight paraffin sulfonate (sodium salt) and 1.5 % by weight of an ethoxylated fatty alcohol (Defosol 12/18/3 from Defotec), and the remainder water.

The contents of the other bucket remain untreated.

After 24 hours, the untreated sample is found to develop a strong odour. Odour development starts only after 40 hours in the case of the treated sample.

Example 2: Example 1 is repeated, but 1 ml of the mixture indicated above is added.

Odour development starts after 30 hours in the case of the untreated sample. Odour development starts only after 70 hours in the case of the treated sample.

Example 3: A water bucket that can be sealed shut is filled with 20 litres of waste water from a municipal pumping station. Using a peristaltic pump, the water is pumped through a hose 50 m in length (diameter: 1.90 cm (% inch)), the dwell time of the waste water in the hose being two days.

After thirty hours, it is found that a strong odour is developed.

Example 4: Example 3 is repeated, except that 2 ml of the mixture indicated in Example 1 is added. Odour development is found only after 75 hours.

Claims

What is claimed is:

1. A mixture comprising a) from 5 to 25 % by weight of a terpene, b) from 30 to 80 % by weight of an alkali metal nitrate or alkaline earth metal nitrate, c) from 1 to 25 % by weight of an emulsifier and d) from 1 to 25 % by weight of a surfactant, the sum of the individual components being 100 % by weight.

2. Use of a mixture according to claim 1 in treating waste water.

3. A method of treating waste water, characterized in adding a mixture according to claim 1 to the waste water to be treated.

4. A method of treating waste water, characterized in adding to the Waste water to be treated an aqueous mixture comprising a mixture according to claim 1 and from 1 to 50 % by weight water, based on the aqueous mixture, in an amount in the range from 5 to 100 ml/m³ of waste water.