Water Treatment System

Anaerobic System

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Anaerobic treatment differs from conventional aerobic treatment in that no aeration is applied. The absence of oxygen leads to controlled anaerobic conversions of organic pollutants to carbondioxide and methane, the latter of which can be utilized as energy source.

The main advantages of anaerobic treatment are the very high loading rates that can be applied (10 to 20 times as high as in conventional activated sludge treatment) and the very low operating costs. Anaerobic treatment often is very cost-effective in reducing discharge levies combined with the production of reusable energy in the form of biogas. Pay-back times of significant investments in anaerobic treatment technologies can be as low as two years. Anaerobic treatment of domestic wastewater can also be very interesting and cost-effective in countries were the priority in discharge control is in removal of organic pollutants.

COD is basically a measure of organic matter content or concentration. The best way to appreciate anaerobic wastewater treatment is to compare its COD balance with that of aerobic wastewater treatment, as shown in Figure below.

Anaerobic Treatment:
The COD in wastewater is highly converted to methane, which is a valuable fuel. Very little COD is converted to sludge. No major inputs are required to operate the system.

Aerobic Treatment:
The COD in wastewater is highly converted sludge, a bulky waste product, which costs lots of money to get rid of. Oxygen has to be continuously supplied by aerating the wastewater at a great expense in kilowatt hours to operate the aerators.

Anaerobic Wastewater Treatment:
Industrial wastewater anaerobic treatment of wastewater is very well suited for industries discharging highly concentrated (over approximately 1,500 mg COD/l) wastewaters, with nitrogen concentrations that are not too high. The food and food processing industry, beer breweries, soft drink producing factories and paper producing or processing factories, and some chemical industries all discharge wastewaters of this type.

Many applications are directed towards the removal of organic pollution in wastewater, slurries and sludges. The organic pollutants are converted by anaerobic microorganisms to a gas containing methane and carbon dioxide, known as “biogas”.