Odour/treatment

Odours
Bad odour is typically the first sign of septic wastewater as a result of anaerobic bacterial activity in the absence of oxygen or nitrate. Very often this odour is caused by hydrogen sulphide (H₂S). Hydrogen sulphide is a gas which smells like rotten eggs. Due to a very low odour threshold level, even small concentrations of H₂S can be smelt in a wide radius from manholes, pumping stations, treatment plants and industrial factories.
However, anaerobic decomposition of organic material containing sulphur and nitrogen may also result in generation of other odorous compounds. The most frequently detected odorous compounds in wastewater are given in the table:

The odour is very unpleasant and may result in complaints from people living in an area close to the source of the odour. In human terms, the importance of noxious odours is related primarily to the psychological stress it produces. Offensive odour can cause headaches, vomiting, poor appetite and impaired respiration. These problems often lead to negative publicity, media attention and bad reputation. The smell from septic wastewater also produces a poor working environment, and in extreme situations can lead to the breakdown of company and community relations. It may also interfere with human relations, discourage capital investment, lower socio-economic status and deter growth of the tourism industry. This is a situation that can be avoided - not just hidden by the statement that "wastewater usually smells bad". Try NUTRIOX® septicity control !

Health and safety Hydrogen sulphide (H₂S) will form in septic wastewater. This is a very toxic gas, about as toxic as hydrogen cyanide. Due to the volatile character of hydrogen sulphide, the gas will easily be released from water to the atmosphere. Even a low concentration of hydrogen sulphide in the water often produces a high concentration in gas phase. In fairly high concentrations, the gas is deadly. In low concentrations, H₂S has a strong unpleasant odour, but as long as it can be smelt it is not deadly. In higher concentrations, its odour is undetectable because it immediately paralyses the sense of smell, making it even more hazardous. People working at sewage treatment plants and pumping stations are especially at risk if they are consistently exposed to high levels of hydrogen sulphide. Inhabitants close to sewage systems where a leak of H₂S has occurred are subject to the same level of risk. H₂S can cause serious damage to the eyes and respiratory passages and can cause brain damage. Short exposure to concentrations of 500 - 1,000 ppm H₂S will quickly result in respiratory paralysis and death. The occupational limit is set to 10 ppm. This value is mainly based on the experience that this concentration causes a physical effect (eye irritation). No systematic observations are carried out on effects of exposure to concentrations in the range of 1-10 ppm for longer periods. However, there are indications that constant exposure to low concentrations may represent a health risk (headaches, irritability, loss of appetite, poor memory).

Corrosion

NUTRIOX® septicity control is a well proven solution which not only removes hydrogen sulphide, but also prevents septicity. The presence of hydrogen sulphide (H₂S) is the most important factor causing corrosion of both concrete and metal in sewage systems

The lifetime of sewers, pumps and electrical installations can be considerably shortened by corrosion. Concrete is corroded by sulphuric acid, which is formed by the oxidation of hydrogen sulphide by aerobic bacteria (e.g. Thiobacilli) growing on exposed sewer walls under humid conditions. Concrete corrosion is a result of a chemical reaction between sulphuric acid and components in the concrete, resulting in a voluminous precipitate (gypsum). This will weaken the mechanical strength of the concrete and the sewer will eventually collapse when it can no longer tolerate the load. The mechanism for metal corrosion is a chemical reaction, in which hydrogen sulphide reacts with the metal, forming metal sulphides. Corrosion means higher maintenance costs for sewer systems. Damaged pipes will increase the hydraulic strain on systems if there is an infiltration, and the wastewater will also pollute underground water, representing a health risk. Replacement of damaged pipes is a costly and extensive task. In cities and other built-up areas, this kind of maintenance work can also be an additional burden to residents and road-users. The best way to combat corrosion is to prevent it. NUTRIOX® septicity control prevents septicity and corrosion it cauces. Reduced efficiency of the water treatment plant The sewer pipe functions as a biological reactor at the head of the treatment plant, and biological activity in the network is an important part of the total treatment process.

Reduced efficiency of the water treatment plant The sewer pipe functions as a biological reactor at the head of the treatment plant, and biological activity in the network is an important part of the total treatment process

If septic conditions have developed in the network, anaerobic bacteria and hydrogen sulphide (H₂S) will reach the treatment plant. This may reduce the efficiency of the process, as hydrogen sulphide is toxic to both aerobic and anaerobic bacteria in different biological treatment processes. H₂S may also encourage the growth of certain types of filamentous bacteria that cause sludge bulking and poor sedimentation. Because H₂S is oxidised back to sulphate by aerobic bacteria, H₂S in waste water will result in increased oxygen requirement in biological treatment plants. In chemical treatment processes, H₂S can result in increased consumption of chemicals. Increase the efficiency at the treatment plant and reduce your costs by using NUTRIOX® septicity control.