Secondary biological treatment

Wastewater. Phenol is a toxic poUutant to the waterways and has an acute toxicity (- 5 m g/L) to fish. Chlorination of water gives chlorophenols, which impart objectionable odor and taste at 0.01 mg/L. Biochemical degradation is most frequently used to treat wastewater containing phenol. Primary activated sludge, along with secondary biological treatment, reduces phenol content to below 0.1 mg/L (69). 

Kraft pulp mills treat wastewater using primary (physical) and secondary (biological) treatment to reduce pollutant discharges to receiving waters. Kraft mills typically collect and treat the following wastewaters36 ... 

Hajdow MWTP is a typical Polish municipal wastewater treatment plant and consists of primary (mechanical) treatment part and secondary (biological) treatment part. Total treatment procedure lasts about 22 hours. The primary sludge and excess sludge are water reduced separately and go together to the digester. 

Secondary biological treatments are considered to be an effective barrier to most PhCs due to the metabolic and co-metabolic processes at work in these systems [58, 77, 78]. 

Stabilization pond Relatively shallow body of wastewater contained in an earthen basin used for secondary biological treatment. Volume 2(7). 

For problematic waste waters, secondary biological treatment is insufficient to meet the increasingly strict legislative standards on COD, colour and priority pollutants such as pesticide and herbicide residues. Whilst pollution prevention will always be the environmentally preferable option, this is not always practical, and in such cases tertiary treatment with catalysed hydrogen peroxide can present an economical and effective way to achieve compliance. 

Typical concentrations of phosphates found in various waters are given in Table 6-4. In fresh raw domestic wastewater the phosphate is distributed approximately as follows orthophosphate, 5 mg/liter as phosphorus, tripolyphosphate, 3 mg/liter as phosphorus, pyrophosphate, 1 mg/liter as phosphorus and organic phosphates < 1 mg/liter as phosphorus. Secondary biological treatment, and indeed prolonged contact with the microorganisms in raw sewage, ensures the hydrolysis, ("reversion") of condensed phosphates to orthophosphate. Tripolyphosphate, for example, hydrolyzes as follows ... 

Biological degradation (and formation) of transformation products in secondary (biological) treatment can typically be expected to follow traditional Monod kinetics... 

Depending upon the in-plant control methods used within a refinery it may be necessary to add sulfide removal and neutralization to the pretreatment operations listed in Table 12. The oil concentration in the wastewater should be reduced to 50 mg/L in order to insure trouble-free operation in secondary biological treatment facilities. In addition, the presence of oil in a sewer would constitute a fire and... 

Between now and 1985, some 4,000 or more communities in the United States will be building new sewage disposal plants with secondary biological treatment, including those who will have to up-grade primary plants to secondary plants. To this there is added industrial waste treatment business. 

Fig. 3.2. Types of secondary biological treatment methods. (Courtesy EPA.)...

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