I prefer aerobic wastewater treatment, as there are problems with anaerobic microorganisms. Here is how: Anaerobic digestion is a three-stage process. In the first stage, the complex insoluble organics are hydrolyzed to simple soluble organics by the extra cellular enzymes. During this stage, the cellulose and starch are hydrolyzed to simple sugars, while proteins bifurcate into amino acids. In the second stage, called the acid phase, the acid formers (various species of Pseudomonos, Alcaligens, Flavobacterium, Escherichia and Aerobacter) convert simple organics to organic fatty acids (acetic acid). This results in higher acid concentration and low pH. In the third stage, called methane phase, methane formers utilize the organic acids and metabolized them to methane and carbon dioxide. Amino acids give rise to ammonia, which in turn, neutralize the remaining acids. Methane formers (species of Methanobacterium, Methanococcus and Methanosarcina) are highly frail in nature. They are strict anaerobes, grow over a wide range of temperature, difficult to cultivate and, they remain inalienable. They are highly sensitive to low pH conditions. These concomitant reactions in actual digestion occur simultaneously. Flawless performance of the digester will take place only when there is a balanced bacterial population of acid formers and methane formers, or, in other words, the volatile acids production equals volatile acids breakdown. If the volatile acids formation is greater than its breakdown (which usually is the case, in actual digesters), the pH lowers, inhibition or wash-out of methane formers occurs and, the process fails, biologically.   P L McCarty was the one who invented anaerobic contact process in 1964. In 1969, P L McCarty and C J Young developed anaerobic filters. Lettinga invented upflow anaerobic sludge blanket (UASB) in early 1970s. UASB, and to some extent anaerobic filters found some use in India. India has a large 345 million liters per day capacity upflow anaerobic sludge blanket plant, located at Bharwara, Lucknow, Uttar Pradesh. This is the largest UASB plant in Asia. F H Mughal Karachi, Pakistan

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I prefer aerobic wastewater treatment, as there are problems with anaerobic microorganisms. Here is how:

Anaerobic digestion is a three-stage process. In the first stage, the complex insoluble organics are hydrolyzed to simple soluble organics by the extra cellular enzymes. During this stage, the cellulose and starch are hydrolyzed to simple sugars, while proteins bifurcate into amino acids. In the second stage, called the acid phase, the acid formers (various species of Pseudomonos, Alcaligens, Flavobacterium, Escherichia and Aerobacter) convert simple organics to organic fatty acids (acetic acid). This results in higher acid concentration and low pH. In the third stage, called methane phase, methane formers utilize the organic acids and metabolized them to methane and carbon dioxide. Amino acids give rise to ammonia, which in turn, neutralize the remaining acids.

Methane formers (species of Methanobacterium, Methanococcus and Methanosarcina) are highly frail in nature. They are strict anaerobes, grow over a wide range of temperature, difficult to cultivate and, they remain inalienable. They are highly sensitive to low pH conditions.

These concomitant reactions in actual digestion occur simultaneously. Flawless performance of the digester will take place only when there is a balanced bacterial population of acid formers and methane formers, or, in other words, the volatile acids production equals volatile acids breakdown. If the volatile acids formation is greater than its breakdown (which usually is the case, in actual digesters), the pH lowers, inhibition or wash-out of methane formers occurs and, the process fails, biologically.

 

P L McCarty was the one who invented anaerobic contact process in 1964. In 1969, P L McCarty and C J Young developed anaerobic filters. Lettinga invented upflow anaerobic sludge blanket (UASB) in early 1970s. UASB, and to some extent anaerobic filters found some use in India. India has a large 345 million liters per day capacity upflow anaerobic sludge blanket plant, located at Bharwara, Lucknow, Uttar Pradesh. This is the largest UASB plant in Asia.

F H Mughal

Karachi, Pakistan