Effluent digestion with recycling

Mesophilic (35°C) digestion with recycling of aerobically posttreated digester effluent. 

Digestion With Recycling of Aerobicelly Posttreeted Digester Effluent... 

Digestion With Product Qas and Posttreated Effluent Recycling... 

The 2/ batch unit was operated under conditions of limited aeration (0.12 / /min) at an ambient temperature of about 25 C). The fill-and-draw activated sludge unit was fed daily with 1,667 ml of fresh digester effluent after withdrawing an equal volume of mixed liquor aerated for 24 hours. Selected volumes of the aerator mixed liquor were recycled to the digester to... 

Daily digester effluent was aerated (air flow rate 0.12 f /min) in a 2.0- f culture volume, batch, activated sludge unit operated at ambient temperature. A volume of 1200 ml of aerater content was recycled with 467 ml of fresh feed daily. 

The sludge that is produced from the clarifiers goes into a treatment train typically consisting of an anaerobic digester (AD) having a HRT of 15 to 20 days or more. The liquid effluent from the AD is recycled back to the head of the plant. The gas produced, containing primarily methane and carbon dioxide, can be used for electricity production in gas turbines with the waste heat used to heat the ADs. In some plants the gas is used to heat the digester directly with the excess methane burned (flared). The solids from this process are filter pressed to remove more water, and composted. These treated and stabilized solids, called biosolids, are now suitable for safe land application and often times can be used as a source of fertilizer. 

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