Effluent treatment activated sludge

For biological treatment of composite effluent, the activated sludge model showed better results compared to those obtained by using a unit simulating a trickling filter. Activated sludge treatment yielded an effluent with an average BOD value of 40 mg 1 . ... 

As a result of several studies, the following conclusions regarding viruses in sewage warrant consideration (1) primary sewage treatment has little effect on enteric viruses (2) secondary treatment with trickling filters removes only about 40 percent of the enteroviruses (3) secondary treatment by activated sludge treatment effectively removes 90 percent to 98 percent of the viruses and (4) chlorination of treated sewage effluents may reduce, but may not eliminate, the number of viruses present. 

Comminution Shredding. A mechanical treatment process which cuts large pieces of waste into smaller pieces so that they won t plug pipes or damage equipment. Contact stabilization Contact stabilization is a modification of the conventional activated sludge process. In contact stabilization, two aeration tanks are used. One tank is for separate reaeration of the return sludge for at least four hours before it is permitted to flow into the other aeration tank to be mixed with the primary effluent requiring treatment. 

Inputs from WWTP effluents can also affect the hydrologic and nutrient concentration regimes of recipient streams at different temporal scales. Daily variations of these parameters may be exacerbated in streams below the WWTP input by the diel patterns of the effluent discharge associated with plant operation [46]. In contrast, at the annual scale, seasonal variations of physical and chemical parameters upstream of the WWTP may be dampened by the constant input of additional water and nutrients from the WWTP. At its extreme, naturally intermittent or ephemeral streams may turn into permanent streams downstream of WWTPs [28, 30]. In these effluent-dominated streams, the relative contribution of WWTP inputs may vary widely on an annual basis, as shown by the 3-100% range measured in a Mediterranean stream [47]. Finally, WWTP inputs also cause shifts in the relative availability of N and P as well as in the relative importance of reduced and oxidized forms of N in the stream [30, 47]. The magnitude of these shifts depends on the level of wastewater treatment (i.e., primary, secondary, or tertiary treatment), the type of WWTP infrastructure (e.g., activated sludge reactor. 

It is well documented that WWTP are major contributors of pharmaceuticals and illicit drugs in the aquatic environment, due to their incomplete removal in conventional activated sludge (CAS) treatment, resulting in important loads discharged into river waters through effluent wastewaters (Tables 1 and 2). 

The primary distinguishing feature of the improved activated sludge treatment system is that high-rate DAF is the secondary clarifier for separation of suspended solids from the activated sludge aeration basin effluent, as opposed to secondary sedimentation alone in a conventional activated sludge system. 

The fate of hormones in urban WWTP has been abundantly documented. Several studies reported high removal rates for hormones from the liquid phase of sewage, particularly in those WWTP using activated sludge processes. For instance, removal rates of 40-96%, 40-100%, 40-96%, and 40-98% for, respectively, El, E2, E3, and EE2 were reported in WWTP all around the world. Nevertheless, residual hormone concentrations of < 0.3-100 ng L 1 of El, < 0.2-20 ng L 1 of E2, < 1-275 ng L 1 of E3, and < 0.3-7.5 ng L 1 of EE2 have been detected in treated effluents, which shows that hormones were not completely removed by the treatment processes [82, 84, 86, 90, 95-97]. 

Johnson AC, Belfroid A, Di Corcia A (2000) Estimating steroid oestrogen inputs into activated sludge treatment works and observations on their removal from the effluent. Sci Total Environ 256 163-173... 

Reactive Red 3.1 Activated sludge obtained from domestic and industrial effluent treatment plants Decolorization rates of up to 30 mg L 1 h 1 were observed in case of activated sludge under anaerobic conditions. In anaerobic packed bed reactor [15]... 

Eschenhagena M, Schupplerb M, Oskea IR (2003) Molecular characterization of the microbial community structure in two activated sludge systems for the advanced treatment of domestic effluents. Wat Res 37 3224—3232... 

Binkley J, Kandelbauer A (2003) Effluent treatment-enzymes in activated sludge. In Cavaco-Paulo A, Guebitz GM (eds) Textile processing with enzymes. Woodhead, Cambridge UK, pp 199-221... 

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