Treatment sludges

Under continuous operating conditions, the rest of the sludge is dewatered by two continuous centrifuges. They treat only sludge from the thickener after it has undergone specific polyelectrolyte conditioning. 

The sludge removed from the filter press and the centrifuges is dumped. 

The oil skimmed off on the surface of the API separator is partly reprocessed in the refinery and the rest is incinerated. 

The Aubette plant system (steam cracking and hydrotreating) is used as an example (Fig. 70). Its heat exchangers are made of stainless steel and the Ct concent can be kept lower than 4 meq l by make up water from the canal, despite a concentration rate of 4.5 

Chemical conditioning is based on acid vaccination of the canal water which is used without being softened. The chemicals utilized are a combination of phosphonate, zinc 

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Water Treatment. Flotation in water treatment is used both for the removal of dissolved ions such as Cu ", Cr ", or (PO or surfactants and suspended soHds as in the case of sludge treatment. The final product in this case is purified water rather than a mineral concentrate. Furthermore, water is treated either for drinking purposes (potable water preparation) or safe disposal to the environment. 

Because of the wide variability in sludge characteristics and the variation in acceptability of treated sludges for ultimate disposal (this is a function of the location and characteristics of the ultimate disposal site), it is impossible to prescribe any particular sludge-management plan. In the sections below, general performance of individual sludge-treatment processes and operations is presented. 

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. 

The following are good r erences to obtain information on sludge treatment technologies and applications ... 

Dispersing a gas m a liquid as fine bubbles (e.g., oxygen from air m a suspension of microorganism for fermentation or for activated sludge treatment). 

Donard OFX, Quevauviller P, Bruchet A (1993) Tin and organotin speciation during wastewater and sludge treatment processes. Water Research, 27(6) 1085-1089. 

Sludge treatment (filter press and final disposal)... 

U.S. EPA, Process Design Manual for Sludge Treatment and Disposal, Report EPA 6251-174-006, U.S. EPA, National Technical Information Service, Springfield, VA, 1974. 

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 typical overloaded conventional complete-mix activated sludge treatment plant (shown in Figure 27.11) has been described in Section 27.3.3. The same conventional treatment plant can be improved by the addition of a secondary flotation clarifier (shown in Figure 27.12). Some advantages of the improved activated sludge system are mathematically presented below. 

The comparable conventional activated sludge system (Figure 27.11), on the other hand, generates 0.0396 MGD of waste sludge with a concentration of 12,500 mg/L. The sludge treatment cost of an improved system will, therefore, be reduced to one half due to a reduction in sludge flow and an... 

Many pilot-scale and full-scale trials involving the use of secondary flotation (Krofta Supracell) in activated sludge treatment plants were conducted by KEC and Lenox Institute of Water Technology (LIWT) (formerly Lenox Institute for Research). Only partial operational data are selected for presentation in this chapter. The readers are encouraged to contact the authors for details. In the illustration of each case history, the true names of the company and its resident engineer involved are omitted for the protection of the Company s privacy. 

Many pilot plant operations have been conducted by KEC through Krofta Apparatebau G.M.B.H., Germany, under direct supervision of Mrs Elisabeth Hurst-Gaul, Manager. The use of a Krofta Supracell DAF clarifier for secondary clarification in the activated sludge treatment plant has been concluded to be feasible. This chapter summarizes the results of her investigation. 

A conventional activated sludge treatment plant in Flouston, Texas, is heavily overloaded. KEC and the LIWT evaluated the flotation characteristics of MLSS in the Krofta Supracell... 

For an existing conventional activated sludge treatment plant having a fungi problem, installing a DAF clarifier between the existing aeration basin and the final sedimentation clarifier (shown in Figure 27.12) will be the remedy. 

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