Water Reuse Potential for Expanding the Nation's Water Supply Through Reuse of Municipal Wastewater (2012) / Chapter Skim
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4 Wastewater Reclamation Technology
4 Wastewater Reclamation Technology
Pages 67-86
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From page 67... ...
Preliminary steps ter reuse application, reclaimed water quality objectives, include measuring the flow coming into the plant, the wastewater characteristics of the source water, com- screening out large solid materials, and grit removal to patibility with existing conditions, process flexibility, protect equipment against unnecessary wear. Primary operating and maintenance requirements, energy and treatment targets settleable matter and scum that floats chemical requirements, personnel and staffing require- to the surface.
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From page 68... ...
Coagula on Filtra on Sludge P essing Sludge Processing R Residuals: -B -Brines -S -Spent carbon Disposa Disposal -S -Spent resins Disposal al -Sludges FIGURE 4-1 Treatment processes commonly used in water reclamation. Note that some or all of the numerous steps represented under advanced processes may be employed, depending on the end-product water quality desired and whether engineered natural processes are also used.
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From page 69... ...
TABLE 4-1 Treatment Processes and Efficiencies to Remove Constituents of Concern during Water Reclamation Constituents of Concern Pathogens Bromate Trace Organics and Energy Residual Process Protozoa Bacteria Viruses Nitrate TDS Boron Chorate Metals DBPs Nonpolar Polar Requirements Generationa Cost Engineered Systems: Physical Filtration Moderate Moderate Low None None None None Low None None None Low Low Low PAC/GAC Low Low Low None None None Low Low Moderate High Low Low Low Moderate MF/UF High Moderate Low None None None Low Low Low Low None Moderate Low Moderate NF/RO High High High High High Moderate High High Moderate High High High High High Engineered Systems: Chemical Chloramine Low Moderate Low None None None None None None None None Low None Low Chlorine Moderate High High None None None None None None Low to Low to Low None Low moderate moderate Ozone Moderate High High None None None None None Low High High High None High UV High High Moderate None None None None None None None None Moderate None Low High High High None None None None None Low High High High None High UV/H2O2 Engineered Systems: Biological BAC Low Low Low None to None None Low Low Low to Moderate Moderate Low None to low Low low moderate Natural Systems SAT High High Moderate High None None Low to High High High Moderate Low None Low moderate to High Riverbank High High Moderate High None None Low to High High High Moderate Low None Low Filtration moderate to High Direct inj. Moderate Low Low Low None None Low to High Moderate Low None Moderate None Low to moderate moderateb ASR Moderate Moderate Moderate Moderate None None Low High Moderate Moderate Low to Low None Low moderate Wetlands Low to Low to Low Moderate None None Low Moderate Low Low to Low Low None Low moderate moderate to high moderate Reservoirs Low to Low Low Low to None None Low Moderate Low Low Low Low None Low moderate moderate to high NOTE: The qualitative values in the table represent the consensus best professional judgment of the committee.
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From page 70... ...
are generated on-site. In drinking water applications, The relationships between C ∙t a nd microbial chlorine and hypochlorite remain the most common inactivation may be affected by water quality (e.g., disinfectants, although they are decreasing in preva- temperature, turbidity, pH)
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From page 71... ...
. The spectrum of these will not be reviewed ADVANCED ENGINEERED TREATMENT in this report, but in general, chlorine and ozone can react with organic materials to produce stable disinfection Advanced engineered unit processes and operations byproducts (which may or may not be halogenated)
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From page 72... ...
Although chemical tion plants compared with reclaimed water provided by precipitation for phosphorus removal is practiced in a membrane filtration plant. many water reclamation facilities, biological phos- As an alternative to depth filtration, surface filtraphorus removal requires no chemical input.
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From page 73... ...
. Removal of Organic Matter and Trace Organic Chemicals The following sections describe processes that are designed to remove organic matter and trace organic chemicals from reclaimed water.
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From page 74... ...
. First, whereas the terms micro For reuse projects that require removal of disand ultrafiltration nominally refer to pore sizes that solved solids and trace organic chemicals and where have cutoff characteristics as shown in Figure 4-3, the a consistent water quality is desired, the use of inteactual pore sizes in today's commercial membranes grated membrane systems incorporating MF or UF often vary over a wide range.
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From page 75... ...
. NF membranes, while water RO membranes ranged widely, with one manuachieving a similar product water quality with respect facturer consistently demonstrating complete rejection to TOC and trace organic chemicals, can be operated in both types of tests.
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From page 76... ...
with a grain diameter of less byproducts from ozonation of trace organic chemicals, than 0.074 mm or granular activated carbon (GAC) , such as steroid hormones and pharmaceuticals, also which has a particle diameter greater than 0.1 mm.
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From page 77... ...
. However, the ability of chlorine to effectively oxidize Chemical oxidation is commonly employed in trace organic chemicals, including steroid hormones, is water treatment to achieve disinfection, as described a function of contact time and dose.
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From page 78... ...
However, ozone does not provide a complete tion system. To mitigate salinity problems associated barrier to trace organic chemicals, and there are certain with local water reuse activities, especially in inland chemicals that are not amendable to oxidation (e.g., applications, partial desalination of reclaimed water chlorinated flame retardants; artificial sweeteners)
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From page 79... ...
Some tiobjective treatment processes targeting the removal of installations might also exhibit deterioration of water pathogens, particulate and suspended matter, DOC, quality in the recovered water due to biogeochemical trace organic chemicals, and nutrients, either as the key reactions in the subsurface that were not anticipated. treatment process or as an add-on polishing step.
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From page 80... ...
when reclaimed water is applied with total nitrogen Previous studies have characterized the transfor- concentrations in excess of 20 mg N/L. At such high mation and removal of select trace organic chemicals concentrations, the wetting and drying cycles of the during SAT for travel times ranging from ~1 day to 8 spreading basins cannot meet the nitrogenous oxygen years (Drewes et al., 2003a.
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From page 81... ...
forces due to streamflow prevent the accumulation of For potable reuse projects, different regulatory particulate and colloidal organic matter in the infiltrarequirements exist regarding the minimum retention tion layer. time of reclaimed water in the subsurface prior to Biodegradation of organic matter represents a key extraction.
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From page 82... ...
(2011) studied the fate and transport of bulk organic matter and a suite of 22 trace organic chemicals during the surface-spreading recharge operation using a smaller but well-instrumented test basin at this facility.
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From page 83... ...
. Concentration of Select Trace Organic Chemicals in Reclaimed Water After Surface Spreading Avg.
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From page 84... ...
water quality benefits, engineered treatment wetlands Infiltration rates of direct injection wells are much frequently serve as habitat for birds and provide recrehigher than infiltration rates in spreading basins, al- ational and educational benefits for the community. In though direct injection wells can become clogged at addition, they have the potential to serve as breeding the interface of the gravel envelope of a well and the grounds for mosquitoes and other vectors.
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From page 85... ...
Concentrations of trace organic chemiwater interface and nitrate-reducing microbes below cals usually are quite low and it is difficult to assess the the surface also can transform organic contaminants potential for removal from reservoirs. There is a clear as they metabolize decaying plants and organic mat- research need to better understand the contribution of ter present in the reclaimed water.
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From page 86... ...
As a result, many coastal utilities A portfolio of treatment options, including en- still favor RO to mitigate salinity and risks from trace gineered and managed natural treatment processes, organic chemicals to produce high-quality water for exists to mitigate microbial and chemical contami- potable reuse. However, limited cost-effective connants in reclaimed water, facilitating a multitude of centrate disposal alternatives hinder the application of process combinations that can be tailored to meet membrane technologies for water reuse in inland comspecific water quality objectives.
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