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035			_a.b10676831
099		9	_aAIT Thesis no. 819
100			_aBonotan-Dura, F. M.
245	1	4	_aThe application of constant recycle solids concentration in the activated sludge process
260			_aBangkok : _bAsian Institute of Technology, _c1975
300			_a71 p.
490	1		_aThesis ; _vno. 819
500			_aA thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering of the Asian Institute of Technology, Bangkok, Thailand.
502			_aThesis (M.Eng.) - Asian Institute of Technology, 1975
520			_aThe applicability of the new model (GAUDY 'S MODEL) for completely mixed activated sludge treatment holding the recycle solids concentration as a system constant was investigated using an actual industrial organic wastewater. Short-term experiments were conducted at various dilution rates (1/8, 1/6, 1/4, 1/2, 1/1.5 hr-1 ) for two recycle solids concentration values (5,000 and 7,000 mg/l). The influent substrate concentration was maintained at 1,000 mg/l COD and the hydraulic recycle ratio, a, at 0.3.The reactor biological solids and effluent COD were observed to remain quite steady lending an experimental basis t o the assumption of steady state in the model. High COD removals (for example, 80% compared with 20% for once-through system at a dilution rate of 1/2 hr-1 ) highlighted this mode of operation, The maximum specific growth rate (um) of the heterogeneous microbial population was found to be nearly the same as that for the once-through system. To evaluate the predictability of the new model, the "Monad" parameter m, the saturation constant (K8 ), and the yield coefficient (Y) are used. For ECKENFELDER's Model, values of the substrate removal rate constant (K), mass yield rate coefficient (a), endogenous respiration rate coefficient (b) and the biodegradable fraction of the volatile suspended solids (x) need to be known; for McKINNEY's Model, the metabolism constant (KM), synthesis factor (Ks) and endogenous factor (Ke) have to be evaluated. The term x in ECKENFELDER's formula is still being refuted; the term K is empirical. Evaluation of McKINNEY 's constant is still being investigated. Of the three models, only GAUDY's model is closely tied to the accepted principles of microbial growth. At the range of dilution rates of engineering significance (D < 0.5 hr-1 ), GAUDY's model has been shown to provide higher predictability than ECKENFELDER's or McKINNEY's model. At higher dilution rates (D > 0.5 hr-1 ) wherein the biological solids are being washed out; GAUDY 's model loses its predictive value. Furthermore, at this range, the assumption of negligible substrate concentration in the recycle no longer holds true. The optimum dilution rate for a constant recycle solids concentration between 5,000 to 7,000 mg/l has been found to be 1/4 hr-1 (a reactor detention time of only 3.1 hours).
650	1	0	_aWater _xPurification
650	1	0	_aSewage _xPurification _xActivated sludge process
700	1		_aYang, Yi Ping, _eChairperson
700	1		_aPescod, M.B., _eExamination Committee
700	1		_aNguyen Cong Thanh, _eExamination Committee
700	1		_aHtun, Maung Nay, _eExamination Committee
710	2		_aGovernment of the United Kingdom, _eScholarship Donor
810	2		_aAsian Institute of Technology. _tThesis ; _vno. 819
856			_3Full-Text _uhttp://203.159.5.9/ait-thesis/detail.php?q=B24063
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