Tertiary treatments

Tertiary treatment. Tertiary or polishing treatment prepares the aqueous waste for final discharge. The final quality of the effluent depends on the nature and flow of the receiving water. Table 11.3 gives an indication of the final quality required. ... 

Ultrafiltration. Ultrafiltration was described under pretreatment methods. It is used to remove finely divided suspended solids, and when used as a tertiary treatment, it can remove virtually all the BOD remaining after secondary treatment. 

Process water streams from vinyl chloride manufacture are typically steam-stripped to remove volatile organics, neutralized, and then treated in an activated sludge system to remove any nonvolatile organics. If fluidized-bed oxychlorination is used, the process wastewater may also contain suspended catalyst fines and dissolved metals. The former can easily be removed by sedimentation, and the latter by precipitation. Depending on the specific catalyst formulation and outfall limitations, tertiary treatment may be needed to reduce dissolved metals to acceptable levels. 

Continued recycling of effluent would soon give an unusable product, and tertiary treatment, although expensive, is essential. In some instances, considerable amounts of water can be saved by careful housekeeping and process change. 

There are four stages preliminary, primary, secondary, and tertiary treatment processes, which differ mainly by the number of operations performed on the waste steams (2,3). 

Fluidized-bed powdered activated carbon systems represent another important process. The use of activated carbon for the tertiary treatment of secondary sewage effluents has been used extensively. Powdered carbon is as effective as granular activated carbon for removing the organic impurities from the wastewater. 

Before powdered carbon can be used commercially or reused for tertiary treatment of sewage effluents, a method of regeneration is required. The use of the fluidized bed for regeneration offers the key advantages of excellent temperature and atmosphere control and the ability to process the powdered solids conveniently and continuously. 

Points of Chemical Addition In independent physical-chemical treatment or in phosphate removal in the primary clarifier ahead of biological treatment, chemicals are added to raw sewage. In tertiary treatment for phosphate removal and suspended solids (SS) reduction, they are added to secondary effluent. In both cases, proper mixing and flocculation units are needed. For phosphate removal or improvement of SS capmre in biological secondary treatment, chemicals are often added directly to aeration units or prior to secondary settling units, without separate mixing and flocculation. In some phosphate removal applications coagulants are added at... 

Where effluents require primary, secondary and possibly additional tertiary treatment, attention should be paid to the various treatment processes with regard to personnel safety and public sensitivity to on-site treatment. 

Tertiary treatment is required often to meet the industry or irrigation standards, especially when disinfection is needed. This step is known as water regeneration. Typical tertiary treatment proposed in the literature [23] is composed of the following stages low pressure membrane filtration (e.g., MF) followed by disinfection stage and finally high pressure membrane filtration (e.g., RO). Industrial... 

AOPs are valuable tertiary treatments allowing not only inactivation of a wide spectrum of pathogens but also the removal of a great number of the so-called emerging pollutants (pharmaceutical, personal care products). These are not totally removed during conventional treatment, but remain in the wastewater effluents [33]. Among different alternatives electrochemical oxidation with bom doped diamond electrodes (BDD) has been reported to be effective on eliminating... 

The viability of producing regenerated water for industrial reuse purposes by means of tertiary treatment of WWTP effluents is illustrated in this section, through examples in N Spain. The demonstration has been performed in Spain. The industrial activities in the selected region showed that the potential industrial demand of regenerated wastewater accounted for 5.2 Hm yr which could be obtained from WWTP facilities located 5 km away of the industrial consumers,... 

Effluent pretreatment is necessary when RO is used as tertiary treatment in order to prevent membranes filters form being blocked or abraded. UF offers a powerful tool for the reduction of fouling potential of RO/NF membranes [57]. A typical pretreatment consist of a MF allowing the removal of the large suspended solids form the WWTP effluent followed by UF unit which removes thoroughly suspended solids, colloidal material, bacteria, viruses and organic compounds from the filtrated water. The UF product is sent to the RO unit where dissolved salts are removed. 

Alonso E, Santos A, Solis GJ, Riesco P (2001) On the feasibility or urban wastewater tertiary treatment by membranes a comparative assessment. Desalination 141 39-51... 

Lubello C, Gori AM, de Bemardinis M et al (2003) Ultraflltration as tertiary treatment for industrial reuse. Water Sci Technol 3(4) 161-168... 

Manttari M, Nystron M (2007) Membrane filtration for tertiary treatment of biologically treated effluents from the pulp and paper industry. Water Sci Technol 55(6) 99-107... 

Inputs from WWTP effluents can also affect the hydrologic and nutrient concentration regimes of recipient streams at different temporal scales. Daily variations of these parameters may be exacerbated in streams below the WWTP input by the diel patterns of the effluent discharge associated with plant operation [46]. In contrast, at the annual scale, seasonal variations of physical and chemical parameters upstream of the WWTP may be dampened by the constant input of additional water and nutrients from the WWTP. At its extreme, naturally intermittent or ephemeral streams may turn into permanent streams downstream of WWTPs [28, 30]. In these effluent-dominated streams, the relative contribution of WWTP inputs may vary widely on an annual basis, as shown by the 3-100% range measured in a Mediterranean stream [47]. Finally, WWTP inputs also cause shifts in the relative availability of N and P as well as in the relative importance of reduced and oxidized forms of N in the stream [30, 47]. The magnitude of these shifts depends on the level of wastewater treatment (i.e., primary, secondary, or tertiary treatment), the type of WWTP infrastructure (e.g., activated sludge reactor. 

Fig. 2 Longitudinal changes in nutrient concentrations below the effluent input of a WWTP without tertiary treatment in La Tordera Stream. Values are the average ( SEM) of monthly measurements done over a year (see more details in [47]). In the left panel, note the net decline of ammonium concentration with concomitant net increases in nitrate concentration, suggesting a potential hot spot for nitriflcation. However, in the latest meters downstream, dissolved inorganic nitrogen (DIN) tends to decrease, which indicates net lost of DIN possibly due to denitrification. The right panel shows net changes in phosphate and dissolved organic carbon (DOC) concentrations. While phosphate does not exhibit any clear trend on an annual basis, DOC seems to decline similarly to DIN, which supports the relative dominance of denitrification...

Partial recycling of treated water after biological treatment will usually require additional polishing (tertiary treatment). This may include chemical addition, flocculation, and DAF. This is BAT according to the EC.38... 

Vourch et al49 studied the applicability of the RO process for the dairy industry wastewater. The treated wastewater total organic carbon (TOC) was <7 mg/L. It was found that in order to treat a flow of 100 m3/d, 540 m2 of the RO unit is required with 95% water recovery. Dead-end NF and RO were studied for the treatment of dairy wastewater.50 Permeate COD, monovalent ion rejection, and multivalent ion rejection for the dead-end NF were reported as 173-1095 mg/L, 50-84%, and 92.4-99.9%, respectively. When it comes to the dead-end RO membranes, the values for permeate COD, monovalent ion removal, and multivalent ion removal were 45-120 mg/L, >93.8%, and 99.6%, respectively. Membrane filtration technology can be better utilized as a tertiary treatment technology and the resultant effluent quality will be high. There can be situations where the treated effluents can be reused (especially if RO is used for the treatment). 

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