CEE Oct-Dec 2012

1.10 uo llO LtO .... i $uo ~ uo .... uo 170 uo ISIOON"""' lOlOONN/'h ri11ure II Par,11/el Ver~us Caw·,rde are the results shown for the "Turbo CVC" solution, at the 3 loads and at 6.5m water column), see Figure 13. Good control is as least as important One can easily choose an effective air blower technology without achieving the desired savings, because it requires overal l control which constantly optimizes the operating conditions, if one is to make full use of the energy saving potential. The largest consumer of energy, it is precisely this process that has to be optimized, to achieve significant energy savings of 20 per cent to more than 60 per cent. However, in most cases there will be a need for significant investment in a changeover to more efficient air supply and associated control equipment, so typically the investment would repay itself in less than 12-36 months. At the same time, it must be taken into account that efficient bottom aeration provides better regulation capability, therefore, an improvement in the treatment process, and the possibility to increase the treatment plant loading without increasing tank volume. Lower Biochemical Oxygen Demand (BOD) I Chemical Oxygen demand (COD), N 2 and P 2 levels in the effluent also contributes positively to the overall economy and the total C0 2 emissions are improved simultaneously, by the use of more energy-efficient systems. Centrifugal or turbo blowers are the most energy-efficient technology and deep aeration tanks appear above all to provide the most efficient solution. following parameters must as a minimum be .--------- - - ------------, included in efficient control of the air supply: 1. Control according to a Dissolved Oxygen Level (DOL) set point based on the concentrations of ammonia and nitrates so that the air supply is adjusted to suit the current operating conditions and effluent quality demands. 2. A control method that ensures that the blowers are always working against the lowest possible operating pressure. 3. The use of the 'Most Open Value' control philosophy, whereby at least one of the air control valves is maintained at least 70 per cent to 80 per cent open to reduce the pressure loss across the valves. 4. The use of flow meters to efficiently control the air valves and avoid 'hunting '. 5. The use of an efficient air blower sequence philosophy, so that the right number of blowers are always on line. 6. Do not put too much 'safety' on pressure and flow in the choice of air blower size, as a too big air blower is inefficient. Conclusions Since the air supply in an activated sludge wastewater treatment plant is by far the 1,00% 0,00% o so 1 oo 150 200 260 Joo 350 400 •so soo mmVs Fi11ure 14: [nergy s.n ings with ,, rcYiucllon nt th£• pre~wre­ ~et tn fJl)lnt c i 36.00% -t----t---+----+--t---1---1 § 30,00% +---t-- -t-----t--t---t- .. 8 26,00% +---+---+---+---+----: ~ 20,00% +----+----+---+-- ... Ji 16,00% +--- -+----+--– fti !$ 10,00% +--- +--+. E "tl ~ 6,00% 0,00% 1,600 2,000 2,600 3,000 3.600 4,000 ~600 OOl.mg/1 lrguf(• I 'i. lncrt',I"Yf Cllfl>llmptron u 1/h .m C'\C ew1c•/1 lu81r cl\ ' II''" /c•H•I (/)()/ I 20