High rate clarifiers

FIG. 18-89 Reactor-clarifier of the high-rate solids-contact type. (EIMCO Process Equipment Co.)... 

Softening lime-soda (high-rate, solids-contact clarifiers) 3.7... 

The first system, shown in Figure 6.6, is identical to the conventional reduction-precipitation in chemistry (i.e., neutralization, chromium reduction, pH adjustment, metal hydroxide precipitation, and so on). However, a flotation-filtration clarifier (Tank T101SF, as shown in Figure 6.6) is used. The unit consists of rapid mixing, flocculation, high-rate DAF, and sand filtration.1557... 

The modified reduction-flotation wastewater treatment system (Figure 6.5) will be very attractive if all or most of an existing wastewater treatment facilities are to be reused. The high-rate DAF clarifier is a very low-cost clarification unit. 

Several high-rate air flotation clarifiers (both DAF and dispersed air flotation) with less than 15 min of detention times have been developed for groundwater decontamination, industrial effluent treatment, resources recovery, and water reclamation. Both insoluble and soluble impurities such as... 

A description is given of a unique solution for the problems of overloaded conventional activated sludge systems. A high-rate dissolved air flotation (DAF) clarifier is applied in series between the... 

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. 

A relatively new design of a high-rate DAF unit uses a shallow bed system (Supracell) with only 3 minutes of retention time and operated at an overflow rate of 140Lpm/sqm (3.5 gpm/sq ft) [42]. This unit has been used for industrial and municipal wastewater treatment and offers lower capital cost and headroom requirements. It was installed at a petrochemical complex in Texas as a secondary clarifier to improve the operation and the capacity of an existing activated sludge system [43]. In recent years, nitrogen has replaced air in covered DAF systems because of the potential for explosion. These systems are called dissolved nitrogen flotation (DNF) systems. The operations of DAF and DNF are similar. 

Chemical precipitation of the newly released phosphate in the phosphate stripper effluent (i.e., a P-rich, low-volume sidestream containing 40-80 mg/L P amounting to about 10-15% of the total wastewater flow) using lime, ferric chloride, or alum, and subsequently flotation of the P-rich precipitated chemical sludge for reuse as a fertilizer using a high-rate DAF clarifier (15 min DT). 

Clarification (after 30-min flocculation) Softening lime-soda (high-rate, solids-contact clarifiers) Softening lime-sludge 5-10 20-45 0.6-2.5 1-1.3 3.7... 

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