Three major questions usually arise when a particular type of pollution has been id- tified: 1 How serious is the pollution? This book is one of the volumes of the Handbook of Environmental Engineering series. The principal intention of this series is to help readers f- mulate answers to the last two questions above. Case Study of Packed Tower Aeration. Water Quality Problems. Engineering Applications. Water Chloridation and Chloramination.
Potable Water Chloramination. Waste Chlorination and Stabilization. Volume 20 , Issue 4 November Pages Related Information. Close Figure Viewer. Browse All Figures Return to Figure. Previous Figure Next Figure. Email or Customer ID. Forgot password? Old Password. New Password. Password Changed Successfully Your password has been changed. Returning user.
Request Username Can't sign in? Forgot your username? Figure 36 shows a phosphate removal process. This process needs long narrow tanks for maintenance of plug flow. The nitrification and denitrification processes are responsible for N 2 O production Figure Schematic illustration of nitrification and denitrification processes that are responsible for N2O release . Phytoremediation is a treatment process that solves environmental problems by implementing plants that abate environmental pollution without excavating the pollutants and disposing them elsewhere.
Phytoremediation is the abatement of pollutant concentrations in contaminated soils or water using plants that are able to accumulate, degrade, or eliminate heavy metals, pesticides, solvents, explosives, crude oils and its derivatives, and a multitude of other contaminants and pollutants from water and soils. Figures 39 through 44 show the designs of constructed wetlands where the phytoremediation takes place. Components of a horizontal flow reed bed: 1 drainage zone consisting of large rocks, 2 drainage tube of treated effluent, 3 root zone, 4 impermeable liner, 5 soil or gravel, 6 wastewater distribution system, and 7 reeds .
The incorporation of heavy metals, such as mercury, into the food chain may be a deteriorating matter. Phytoremediation is useful in these situations, where natural plants or transgenic plants are able to phytodegrade and phytoaccumulate these toxic contaminants in their above-ground parts, which will be then harvested for extraction. The heavy metals in the harvested biomass can be further concentrated by incineration and recycled for industrial implementation. Rhizofiltration is a sort of phytoremediation that involves filtering wastewater through a mass of roots to remove toxic substances or excess nutrients.
Phytoaccumulation or phytoextraction implements plants or algae to remove pollutants and contaminants from wastewater into plant biomass that can be harvested. Organisms that accumulate over than usual amounts of pollutants from soils are termed hyperaccumulators, where a multitude of tables that show the different hyperaccumulators are available and should be referred to. In the case of organic pollutants, such as pesticides, explosives, solvents, industrial chemicals, and other xenobiotic substances, certain plants render these substances non-toxic by their metabolism and this process is called phytotransformation.
In other cases, microorganisms that live in symbiosis with plant roots are able to metabolize these pollutants in wastewater. Figure 45 shows the tissues where the rhizofiltration, phytodegradation, and phytoaccumulation take place. Vermiculture, or worm farming, is the implementation of some species of earthworm, such as Eisenia fetida known as red wiggler, brandling, or manure worm and Lumbricus rubellus , to make vermicompost, also known as worm compost, vermicast, worm castings, worm humus, or worm manure, which is the end-product of the breakdown of organic matter and considered to be a nutrient-rich biofertilizer and soil conditioner.
Vermiculture can be implemented to transform livestock manure, food leftovers, and organic matters into a nutrient-rich biofertilizer. The potential use of earthworms to break down and manage sewage sludge began in the late s [ 20 ] and was termed vermicomposting. Vermifilter is widely used to treat wastewater, and appeared to have high treatment efficiency, including synchronous stabilization of wastewater and sludge [ 22 , 23 , 24 ].
Vermifiltration is a feasible treatment method to reduce and stabilize liquid-state sewage sludge under optimal conditions [ 24 , 25 , 26 ]. Vermicomposting involves the joint action of earthworms and microorganisms [ 24 , 27 , 28 ], and significantly enhances the breakdown of sludge. Earthworms operate as mechanical blenders and by comminuting the organic matter they modify its physical and chemical composition, steadily decreasing the C:N ratio, increasing the surface area exposed to microorganisms, and making it much more suitable for bacterial activity and further breakdown.
Throughout the passageway is the earthworm gut, they move fragments and bacteria-rich excrements, consequently homogenizing the organic matter [ 29 ]. An intensified bacterial diversity was found in vermifilter, compared with conventional biofilter without earthworms [ 25 ]. The principle of using earthworms to treat sewage sludge is based on the perception that there is a net loss of biomass and energy when the food chain is extended [ 25 ]. Compared to other technologies of liquid-state sludge stabilization, such as anaerobic digestion and aerobic digestion [ 30 ], vermifiltration is a low-cost and an ecologically sound technique, and more suitable for sewage sludge treatment of small or developing-countries' WWTPs [ 23 , 24 , 25 , 26 , 31 ].
Figure 46 illustrates schematic diagram of a vermifilter, where the earthworms are in the filter bed. An important application is in livestock manure treatment as shown in Figure 47 , where manure is flushed out from the livestock building to a raw effluent tank then the raw effluent is screened to separate the solid waste from manure. The screened effluent is then introduced to the vermifilter to produce the vermicompost. The vermifiltered effluent is then stored in a sedimentation tank.
Afterwards, the vermifiltered effluent is introduced to constructed wetlands where the phytoremediation process takes place. The purified water can be then used to flush the water from the livestock building. Schematic diagram of a manure treatment system containing vermifiltration and phytoremediation processes Amended and redrawn from Morand et al. The microbial fuel cells MFCs allow bacteria to grow on the anode by oxidizing the organic matter that result in releasing electrons.
The cathode is sparked with air to provide dissolved oxygen for the reaction of electrons, protons, and oxygen on the cathode, which result in completing the electrical circuit and producing electrical energy Figure The dissolved inorganic components can be removed by adding an acid or alkali, by changing the temperature, or by precipitation as a solid. The precipitate can be removed by sedimentation, flotation, or other solid removal processes [ 1 ]. Neutralization is controlling the pH of the wastewater whether it is acidic or alkaline to keep the pH around 7.
The lack of sufficient alkalinity will require the addition of a base Table 3 to adjust the pH to the acceptable range. The lack of sufficient acidity will require the addition of an acid to adjust the pH to the acceptable range. Neutralization: Case of acidic wastewater [ 34 ]. Adsorption is a physical process where soluble molecules adsorbate are removed by attachment to the surface of a solid substrate adsorbent. Adsorbents should have an extremely high specific surface area. Examples of adsorbents include activated alumina, clay colloids, hydroxides, resins, and activated carbon.
The surface of the adsorbent should be free of adsorbate. Therefore, the adsorbent should be activated before use. A wide range of organic materials can be removed by adsorption, including detergents and toxic compounds. The most widely used adsorbent is activated carbon, which can be produced by pyrolytic carbonization of biomass [ 1 ]. Figure 49 illustrates the difference between absorption and adsorption.
Activated carbon is the most implemented adsorbent and is a sort of carbon processed to be riddled with small, low-volume pores that enlarge the surface area available for adsorption. Owing to its high level of microporosity, 1 g of activated carbon has a surface area larger than m 2 , which was determined by gas adsorption.
Figure 50 shows a bed carbon adsorption unit.
Physicochemical Treatment Processes: Volume 3 (Handbook of Environmental Engineering)
Note that the carbon can be regenerated by thermal oxidation or steam oxidation and reused. The adsorption capacity, one of the most important characteristics of an adsorbent, can be calculated as follows:. The factors that affect adsorption are [ 3 ]:. Particle diameter: the adsorption is inversely proportional to the particle size of the adsorbent, and directly proportional to surface area.
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Adsorbate concentration: the adsorption is directly proportional to adsorbate concentration. Molecular weight: generally, the adsorption is inversely proportional to molecular weight depending upon the compound weight and configuration of pores diffusion control. The disinfection of wastewater is the last treatment step of the tertiary treatment process. Disinfection is a chemical treatment process conducted by treating the effluent with the selected disinfectant to exterminate or at least inactivate the pathogens.
The rationales behind effluent disinfection are to protect public health by exterminating or inactivating the pathogens such as microbes, viruses, and protozoan, and to meet the wastewater discharge standards. The purpose of disinfection is the protection of the microbial wastewater quality. The ideal disinfectant should have bacterial toxicity, is inexpensive, not dangerous to handle, and should have reliable means of detecting the presence of a residual.
The chemical disinfection agents include chlorine, ozone, ultraviolet radiation, chlorine dioxide, and bromine [ 3 ]. Chlorine is one of the oldest disinfection agents used, which is one of the safest and most reliable. It has extremely good properties, which conform to the aspects of the ideal disinfectant. Effective chlorine disinfection depends upon its chemical form in wastewater.
The influencing factors are pH, temperature, and organic content in the wastewater [ 3 ]. When chlorine gas is dissolved in wastewater, it rapidly hydrolyzes to hydrochloric acid HCl and hypochlorous acid HOCl as shown in the following chemical equation:. Free ammonia combines with the HOCl form of chlorine to form chloramines in a three-step reaction, as follows:.
Figure 51 illustrates the chlorination curve, where the formation of chloramines occurs at the breakpoint. The free chlorine residual first rises then falls until the reaction with ammonia has been completed. As additional chlorine is applied and ammonia is consumed, the chlorine residual rises again. Dechlorination is a very important process, where activated carbon, sulfur compounds, hydrogen sulfide, and ammonia can be implemented to minimize the residual chlorine in a disinfected effluent prior to discharge.
Activated carbon and sulfur compounds are the most widely used [ 3 ]. The dechlorination reactions with the abovementioned compounds are described in the following equations:. Ozone O 3 is a very strong oxidant typically used in wastewater treatment. Ozone is able to oxidize a multitude of organic and inorganic compounds in wastewater. These reactions cause an ozone demand in the treated wastewater, which should be fulfilled throughout wastewater ozonation prior to developing an assessable residual.
Ozone should be generated at the point of application for use in wastewater treatment as ozone is an unstable molecule [ 3 ]. Figure 52 illustrates the corona discharge method for making ozone. Ozone is generally formed by combining an oxygen atom with an oxygen molecule O 2 as follows:. Ultraviolet UV radiation is a microbial disinfectant that leaves no residual. It requires clear, un-turbid, and non-colored water for its implementation.
The commercial UV disinfection systems use low- to medium-powered UV lamps with a wavelength of nm [ 3 ]. The UV dosage can be calculated as follows:. The advantages of UV radiation are: 1 directly effective against the DNA of many microorganisms, 2 not reactive with other forms of carbonaceous demand, and 3 provides superior bactericidal kill values while not leaving any residues.
The advantage is often the disadvantage, because power fluctuations, variations in hydraulic flow rates, and color or turbidity can cause the treatment to be ineffective [ 3 ]. Additionally, cell recovery and re-growth of the damaged organisms because of the inactivation of their predators and competitors has come to light. Ion exchange IX is a reversible reaction in which a charged ion in a solution is exchanged with a similarly charged ion which is electrostatically attached to an immobile solid particle.
The most common implementation of ion exchange method in wastewater treatment is for softening, where polyvalent cations e. Practically, wastewater is introduced into a bed of resin. The resin is manufactured by converting a polymerization of organic compounds into a porous matrix. Typically, sodium is exchanged with cations in the solution [ 34 ].
The bed is shut down when it becomes saturated with the exchanged ions, where it should be regenerated by passing a concentrated solution of sodium back through the bed. Figure 53 shows the schematic illustration of organic cation-exchange bead. Figure 54 shows a typical ion exchange resin column. Table 4 shows the ion preference and affinity for some selected compounds. Ion preference and affinity for some selected compounds [ 3 ].
The principal advanced physicochemical wastewater treatment processes are elucidated in Table 5. Principal advanced physicochemical wastewater treatment processes [ 1 ]. On the other hand, there are some computer programs for planning and designing WWTPs Figures 57 , 58, and WWTP showing: a layout of the plant, b wastewater process flow diagrams, and c sludge process flow diagram.
Wastewater treatment: 1. Storm water overflow; 2. Secondary sedimentation; 7. Sludge treatment: A and B are administrative areas .
Summary of the main process options commonly employed at both domestic and industrial WWTPs. Not all of these unit processes may be selected, but the order of their use remains the same . The recent developments elucidate that subsequent to the physical treatment processes the primary treatment the biological treatment processes come in turn as secondary treatment and precede the chemical treatment processes, which constitute the tertiary treatment.
Microbial fuel cells, phytoremediation, and mycoremediation are the focus of the future development in this field. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3. Help us write another book on this subject and reach those readers.
Advanced Physicochemical Treatment Processes
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Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Abstract This chapter elucidates the technologies of biological and chemical wastewater treatment processes.
- Modern Science, Metaphysics & Mathematics.
- Advanced Physicochemical Treatment Technologies.
- 4 Unit operations for producing clean drinking water.
Keywords Wastewater treatment biological treatment chemical treatment bioremediation phytoremediation mycoremediation vermifiltration treatment plant. Introduction The chapter concerns with wastewater treatment engineering, with focus on the biological and chemical treatment processes. Overview 3. Wastewater treatment techniques Wastewater, or sewage, originates from human and home wastewaters, industrial wastes, animal wastes, rain runoff, and groundwater infiltration.