- Toxic Waste
- Contaminated Water
- Ibc disposal.
- Tanalised timber
- Waste disposal
- Tank cleaning.
Algaecides are chemicals that kill algae and blue or green algae, when they are added to water. Examples are copper sulphate, iron salts, rosin amine salts and benzalkonium chloride. Algaecides are effective against algae, but are not very usable for algal blooms for environmental reasons.
The problem with most algaecides is that they kill all present algae, but they do not remove the toxins that are released by the algae prior to death.
Foam is a mass of bubbles created when certain types of gas are dispersed into a liquid. Strong films of liquid than surround the bubbles, forming large volumes of non-productive foam.The cause of foam is a complicated study in physical chemistry, but we already know that its existence presents serious problems in both the operation of industrial processes and the quality of finished products. When it is not held under control, foam can reduce the capacity of equipment and increase the duration and costs of processes.
Antifoam blends contain oils combined with small amounts of silica. They break down foam thanks to two of silicone’s properties: incompatibility with aqueous systems and ease of spreading. Antifoam compounds are available either as powder or as an emulsion of the pure product.
Antifoam powder covers a group of products based on modified polydimethylsiloxane. The products vary in their basic properties, but as a group they introduce excellent antifoaming in a wide range of applications and conditions.
The antifoams are chemically inert and do not react with the medium that is defoamed. They are odourless, tasteless, non-volatile, non-toxic and they do not corrode materials. The only disadvantage of the powdery product is that it cannot be used in watery solutions.
Antifoam Emulsions are aqueous emulsions of polydimethylsiloxane fluids. They have the same properties as the powder form, the only difference is that they can also be applied in watery solutions.
Detailed information on biocides is also available here
BOILER WATER CHEMICALS
Boiler water chemicals include all chemicals that are used for the following applications:
- Oxygen scavenging;
- Scale inhibition;
- Corrosion inhibition;
- Alkalinity control.
When referring to coagulants, positive ions with high valence are preferred. Generally aluminium and iron are applied, aluminium as Al2(SO4)3- (aluin) and iron as either FeCl3 or Fe2(SO4)3-. One can also apply the relatively cheap form FeSO4, on condition that it will be oxidised to Fe3+ during aeration.
Coagulation is very dependent on the doses of coagulants, the pH and colloid concentrations. To adjust pH levels Ca(OH)2is applied as co-flocculent. Doses usually vary between 10 and 90 mg Fe3+/ L, but when salts are present a higher dose needs to be applied.
Corrosion is a general term that indicates the conversion of a metal into a soluble compound.
Corrosion can lead to failure of critical parts of boiler systems, deposition of corrosion products in critical heat exchange areas, and overall efficiency loss.
That is why corrosion inhibitors are often applied. Inhibitors are chemicals that react with a metallic surface, giving the surface a certain level of protection. Inhibitors often work by adsorbing themselves on the metallic surface, protecting the metallic surface by forming a film.
There are five different kinds of corrosion inhibitors. These are:
1) Passivity inhibitors (passivators). These cause a shift of the corrosion potential, forcing the metallic surface into the passive range. Examples of passivity inhibitors are oxidizing anions, such as chromate, nitrite and nitrate and non-oxidizing ions such as phosphate and molybdate. These inhibitors are the most effective and consequently the most widely used.
2) Cathodic inhibitors. Some cathodic inhibitors, such as compounds of arsenic and antimony, work by making the recombination and discharge of hydrogen more difficult. Other cathodic inhibitors, ions such as calcium, zinc or magnesium, may be precipitated as oxides to form a protective layer on the metal.
3) Organic inhibitors. These affect the entire surface of a corroding metal when present in certain concentration. Organic inhibitors protect the metal by forming a hydrophobic film on the metal surface. Organic inhibitors will be adsorbed according to the ionic charge of the inhibitor and the charge on the
4) Precipitation inducing inhibitors. These are compounds that cause the formation of precipitates on the surface of the metal, thereby providing a protective film.
The most common inhibitors of this category are silicates and phosphates.
5) Volatile Corrosion Inhibitors (VCI). These are compounds transported in a closed environment to the site of corrosion by volatilisation from a source. Examples are morpholine and hydrazine and volatile solids such as salts of dicyclohexylamine, cyclohexylamine and hexamethylene-amine. On contact with the metal surface, the vapour of these salts condenses and is hydrolysed by moist, to liberate protective ions.
Disinfectants kill present unwanted microrganisms in water. There are various different types of disinfectants:
- Chlorine (dose 2-10 mg/L)
- Chlorine dioxide
CHLORINE DIOXIDE DISINFECTION
ClO2 is used principally as a primary disinfectant for surface waters with odor and taste problems. It is an effective biocide at concentrations as low as 0.1 ppm and over a wide pH range. ClO2 penetrates the bacterial cell wall and reacts with vital amino acids in the cytoplasm of the cell to kill the organisms. The by-product of this reaction is chlorite.
Chlorine dioxide disinfects according to the same principle as chlorine, however, as opposed to chlorine, chlorine dioxide has no harmful effects on human health.
Hypochlorite is applied in the same way as chlorine dioxide and chlorine. Hypo chlorination is a disinfection method that is not used widely anymore, since an environmental agency proved that the Hypochlorite for disinfection in water was the cause of bromate consistence in water.
Ozone is a very strong oxidation medium, with a remarkably short life span. It consists of oxygen molecules with an extra O-atom, to form O3. When ozone comes in contact with odour, bacteria or viruses the extra O-atom breaks them down directly, by means of oxidation. The third O-atom of the ozone molecules is than lost and only oxygen will remain.
Disinfectants can be used in various industries. Ozone is used in the pharmaceutical industry, for drinking water preparation, for treatment of process water, for preparation of ultra-pure water and for surface disinfection.
Chlorine dioxide is used primarily for drinking water preparation and disinfection of piping.
Every disinfection technique has its specific advantages and its own application area. In the table below some of the advantages and disadvantages are shown: