Filtering, drinking water treatment

Ozone has many industrial applications. It is a sterilizing and deodorizing agent. It is used for disinfection of filtered drinking water and to purify waste-waters. It also is used in water treatment plants for removal of metal impurities by oxidizing them into insoluble compounds. This removes undesired taste, odor, and color from the water. Ozone also is used for odor control. 

Coarse (dP = 50-100 pm) porous disks are the most frequently applied diffusers in large-scale drinking water treatment systems (Masschelein, 1994). They are seldom used in industrial waste water treatment applications. The reason is that blocking or clogging can easily occur, e. g. by means of precipitation of chemicals, like carbonates, aluminum or ferrous oxides, manganese oxides, calcium oxalate or organic polymers. This is also valid for ceramic filter tubes, which are sometimes used as mass transfer systems in drinking water applications. 

Based on some experimental results, application of the UV/H202 system to eliminate the bromate problem appears to be worthwhile. For example, Kruithof et al. [197], while studying the optimum conditions for disinfection and pesticide removal in a drinking water treatment plant, found that in the range 0.1-2.5 kWh m-3 electric energy (with medium-pressure UV lamps) and 0-25 gm-3 H202, bromate formation was absent. The main drawback was increased assimilable organic carbon, which would necessitate the use of activated carbon filters. 

This pilot-scale has confirmed our earlier observations from full-scale drinking-water treatment plants. Such a detailed and systematic analysis of the amino acid concentrations allow one to monitor the degree of colonization of the filter media. Such colonization presents a problem when it is not wanted or improperly controlled. In these cases, it may be possible to disinfect and then wash the filtey media to decrease the release of amino acids. 

Open high-rate filters are used particularly in drinking water treatment plants because of their high reliability. In water treatment practice, two types of Alters are used most frequently — American and European. They differ particularly in grain size and height of the Alter packing, as well as in the mode of regeneration. 

Granular Activated Carbon, or GAC has a mean particle size between 1-5 mm. It is usually used in fixed bed adsorbers in continuous processes and with low pressure drops, in both liquid and gas phase applications. Most of the gas phase applications (gas purification, solvent recovery, air filtering and gas masks, gas separation by PSA, catalysis, etc.) use GAC. In addition, GAC is displacing PAC in many liquid phase applications such as gold extraction and drinking water treatment GAC has the advantage, compared to PAC, of offering a lower... 

Activated carbon, in powdered (PAC) or granular (GAC) form, has many applications in drinking water treatment. It can be used for removing taste and odor (T O) compoimds, synthetic organic chemicals (SOCs), and dissolved natural ot] nic matter (DOM) from water. PAC typically has a diameter less than 0.15 mm, and can be applied at various locations in a treatment system (Fig. 1). GAC, with diameters ranging from 0.5 to 2.5 mm, is employed in fixed-bed adsorbers such as granular media filters or post filters. Despite difference in particle size, the adsorption properties of PAC and GAC are fundamentally the same because the characteristics of activated carbon (pore size distribution, internal surface area and smface chemistry) controlling the equilibrium aspects of adsorption are independent of particle size. However, particle size impacts adsorption kinetics. 

Another factor is that insufficient contact time to approach equihbrium is generally provided in a drinking water treatment plant for PAG. Specifically, contact times of 2-4 h are generally provided, whereas, approaching equihbrium may take up to 4-5 d for PAG. On the other hand, GAG on GAG-capped filters or post-filter contactors does come nearly to equihbrium. For these reasons (i.e., more favorable equilibriiun capacity, and closer approach to equihbrium), GAG has the potential to provide significantly more effective treatment for difficult to treat transformation products (as well as parent synthetic organic chemicals) in drinking water treatment plants. 

A similar behavior of PFCs was well documented in a drinking water treatment plant in Oakdale, USA. The tap water produced in this plant, the influent water of which is contaminated with PFCs (see Chap. 3 and Fig. 10), has been monitored extensively over the past few years. From Fig. 10 it can be concluded that the short chained PFBA, PFPeA, and PFHxA are not well retained by the treatment plant. This can be seen at early 2007 and early 2009 when the PFCs break through the GAC filter. By the end of 2008, the GAC was regenerated and fresh GAC retained PFCs well for a short period of time. Other PFCs (PFBS, PFHxS and PFOS) were not detected in the treatment plant effluent drinking water. 

The surest way of getting the lead out of your drinking water if you do have dangerous levels is to use a good drinking water treatment device. Be sure to buy a model that states that it removes a high percentage, at least 90%, of the lead from the water it filters. 

Reissmann, F. G. Uhl, W. 2006. Ultrafiltration for the reuse of spent filter backwash water from drinking water treatment. Desalination 198 225-235. 

An important source of lead leading to human exposure is that contained in drinking water. Treatment processes for public water supplies are unlikely to reduce the concentration of filterable lead in the raw water, except where processes such as precipitation water softening are used [25]. Fortunately, however, the concentrations of lead in the raw water are generally fairly low, <0.01 mg dm". Many tap water samples, nevertheless, reveal significantly elevated lead levels, which may occasionally rise to over 1 mg dm . These elevated concentrations are found in areas where the plumbing system is based on lead pipes. 

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