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Presentation on theme: "Module 6: EFFLUENT TREATMENT AND RESIDUALS MANAGEMENT"— Presentation transcript:

Program for North American Mobility in Higher Education

2 Structure of this module
This module is divided into 3 “tiers”, each with a specific goal: Tier 1.- Basic introduction Tier 2.- Case study of the pulp & paper sector Tier 3.- Open-ended problem Each tier contains multiple choice questions at the end.

3 Tier 1. Contents: Introduction Industrial pollution problems.
The petroleum industry. The pulp and paper industry. Programs for reducing pollution. Treatment processes. Process selection. Volume and disposal reduction.

4 Introductory concepts
Effluent Treatment and Residuals Management Tier I: Introductory concepts Tier 1

5 G o a l s: To provide information about the significance of treating effluents from industry and others facilities (or sources) To extreme the necessity of minimize pollutant concentration in the effluents and reduce the wastes production, and, To suggest strategies to reduce pollutant wastes production and their emission to the environment Effluent Treatment is the method of treating or separating pollutants arising from an industrial stream, so that we can return the water to its origin, such as rivers, lakes, etc. Tier 1

6 What is pollution? Pollution means:
…changes in the physical, chemical and biological characteristics of air, land and water …harms for the human and other living species, and, …degradation of the ecosystems ...the undesirable state of the natural environment being contaminated with harmful substances as a consequence of human activities For example, Water Pollution refers to contaminants in aquatic ecosystems (streams, lakes, etc) which render them unfit for a particular use. (Shen, 1999). The environment can absorb only a limited amount of pollutants and wastes, this is the origin of pollution. Tier 1

7 Pollutants can reach: Air Water Solid waste
This module focuses on water pollution from industrial sources Tier 1

8 Water standards: Drinkable Recreation: swimming, fishing. Irrigation
Water impurities may or may not be harmful; it depends on: The amounts and nature of these impurities, The next use to which the water will be put, and The tolerance of these impurities for the next use. Tier 1

9 Types and characteristics of wastewaters:
Contaminants Reason for importance Physical suspended solids They can lead to the development of sludge deposits. Chemical biodegradable organics When discharged untreated to the environment, they lead to the depletion of natural oxygen resources. Nutrients If discharged, they can lead to water pollution. Hazardous Because of their characteristics (e.g.,toxicity, flammability) are dangerous for human health and the environment. Heavy metals They can negatively impact upon biological waste treatment processes. Dissolved inorganic solids They are result of water use, and may have to be removed if the wastewater is to be reused. Biological pathogens Communicable diseases can be transmitted by the pathogenic organism in wastewater. Hazardous wastes are those, which because of its quantity, concentration or characteristics whether physical or chemical, may cause or contribute to an increase in mortality or in serious reversible, or incapacitating reversible illness. Hazardous wastes when improperly transported, stored, treated or managed may pose a potential hazard to human health or environment (Shen, 1999). Tier 1

10 Industrial effluent standards
Water standards Industrial effluent standards Parameter Mexico a USA b Canada c Total suspended solids, (mg/l) 150 27 15 BOD5, (mg/l) 20 56 pH 5-10 6-9 6-10.5 a: Under the official Mexican regulations NOM-001-ECOL-1996 and NOM-024-ECOL-1993 applicable for sewage contaminants to water bodies from paper industry. Source: b: USEPA Source: c: Non-Point source is a non-specific or diffuse source of effluent entering the environment. Non-point sources are directly related to operational areas of the industry. Source: Tier 1

11 Tier 1

12 What is BOD? By definition, BOD is the quantity of oxygen required for the stabilization of the oxidizable organic matter present over 5 days of incubation at 20 oC; that can be explained as a measure of the oxygen required by microbes to degrade a sample of effluent. The organic content of the water can be estimated by the BOD. The organic content of the water can be estimated by the BOD. Tier 1

13 Why should we minimize the use of water?
Water is such an important part of many manufacturing processes that we must consider Effluent Treatment as a part of the main process because of the great amount always involved. Water is abstracted from aquifers and rivers, treated and supply to industries and homes for different uses; used water is supposed to be treated and discharged again into the rivers. Most of the times, this water returns to its natural environment but unfortunately, with a greater heat content or with some substances added. In the USA alone, the amount of water used per day in industrial plants reaches the amount of 130 billion gallons or some 542 million tons (Water Treatment, 1961). It would be necessary to have a tank 50 feet deep, 100 feet wide and over 658 miles long to hold this one day’s supply of water. Nowadays, this demand has totally increased to be much more greater than those quantities mentioned above. Tier 1

14 Why should we minimize the use of water?
It is also important to minimize use of water because of several reasons: Fresh water is often scarce. High costs involved operating effluent treatment plants. Difficult to separate all the elements that pollute water. When thinking about quantities of water spent per day of industrial processes, and realize we don’t have enough natural supplies to provide this quantities forever! Tier 1

15 Industrial pollution problems
Tier 1

16 Industrial pollution problems:
The main pollution problems are related to : Increasing use of water for agriculture. The increase of aqueous effluent to receiving water. Population growth. Industrial products and services. The mental, technical, financial, regulatory and institutional barriers to implement preventive modern technologies. RESULTS: Ecosystems decline. Industrialization social costs. The increase of human diseases. All the sectors of our society generate waste: industry, agriculture, government, transportation, mining, consumers, etc. (Shen,1999) Tier 1

17 The petroleum industry
Tier 1

18 The Petroleum Industry:
Crude oil refining operations involve extracting useful petroleum products from crude oil. Crude oil contains fractions of napthas, gasoline, gas oils, diesel fuel, asphalt, jet fuel and lubrication fuels. Large quantities of production wastes are produced during exploration and production: Wastewater Solid waste Toxic pollutants Tier 1

19 The Petroleum Industry:
Production wastes in the petroleum industry can be grouped broadly into 2 classes: Wastes related to drilling including chemical additives: treatment and disposal of oil drilling wastes takes place either on or off the drilling site. Wastes related to oil production, primarily produced water: The volume of produced water exceeds the volume of drilled wastes. If environmental quality standards are not exceeded the remainder may be discharged to surface waters. The majority of produced water is disposed of underground through injection wells and it is permitted under U.S. EPA control programs. The volume of produced water exceeds the volume of drilled wastes. (Higgins, 1995). ********************** If environmental quality standards are not exceeded the remainder may be discharged to surface waters. The objective of environmental management of produced water is to reduce the quantity and to improve the quality of discharged produced water. Produced water is the largest volume of aqueous waste arising from production operations. The composition of produced waters varies considerably, but typically may include: inorganic salts, heavy metals, solids, production chemicals, hydrocarbons, benzene, polyaromatic hydrocarbons (PAHs) and on occasions naturally occurring radioactive material. Source: Environmental Management in Oil and Gas Exploration and Production (E&P / UNEP, 1997). Tier 1

20 What is refinery effluent?
Petroleum refineries use large volumes of water in their processes. The wastewater contains hazardous chemicals: Tier 1

21 Refinery wastes: Emissions from refineries include: Sulfur oxides
Nitrogen oxides Benzene, toluene and xylene VOC Wastewater containing BOD levels Heavy metals Tier 1

22 Approximate Quantities
Wastes generated: Pollution Approximate Quantities Cooling systems 3.5-5 m3 of wastewater generated per ton of crude. Polluted wastewater BOD mg/l COD mg/l phenol mg/l oil mg/l (desalted water) oil 5000 mg/l in tank bottom benzene mg/l heavy metals mg/l Solid waste and sludge 3 to 5 kg per ton of crude (80 % should be considered as hazardous waste because of the heavy metals and toxic organic presence). VOC emissions 0.5 to 6 kg/ton of crude. Others emissions BTX (Benzene, Toluene and Xylene) 0.75 to 6 g/ton of crude Sulfur oxides kg/ton of crude Nitrogen oxides kg/ton of crude Resource: Pollution Prevention and Abatement Handbook World Bank Group. Water treatment is the treatment of water. Tier 1 (Pollution Prevention and Abatement Handbook World Bank Group)

23 The pulp and paper industry
Tier 1

24 How paper is made: Most of the raw material needed for paper manufacture is supplied by trees. The main steps in the pulp and paper manufacture are raw material preparation, such as wood debarking, and chip making; pulp manufacturing; pulp bleaching; paper manufacturing and fiber recycling. Pulp mills and paper mills may exist separately or as integrated operations. The characteristics of the paper (smoothness, glazed finish) are given by a process called calendering. The paper undergo coating, whereby a thin layer of coating pigment or filler is spread onto the paper surface. Tier 1

25 Pulp and paper industry:
The pulp and paper industry has made significant steps toward conserving water and energy. Significant water reductions are achieved through better reuse methods and by separating cooling water from process water. The waste streams generated in this industry are best classified by their origins as show in the next slide. (Higgins, 1995). Tier 1

26 Types of waste products in the pulp and paper industry:
Material originated in raw materials (dirt and bark with wood). Nonfiber components in wood. Contaminants in waste paper and make-up chemicals. Reaction products (dissolved wood substance from mechanical or chemical action). Fiber fragments. By-products of chemical recovery and combustion. Fiber and nonfiber process looses and discharges of water, air and heat. (Higgins, 1995). Tier 1

27 The pulp and paper industry
Water use and effluent discharges: Liquids discharges from the process contain solids, mainly fiber, fillers, and colloidal and dissolved material. The fiber and fillers are minimized and reused. Colloidal and dissolved materials are by-products of the refining of the fibers or carried over from the pulp mill. Discharges of dissolved material are minimized by washing the stock and displaced carryover from pulp mills and by practicing good water reuse strategies that reduce the volume and concentrations of waste in wastewater. (Higgins, 1995). pp. 526 Tier 1

28 Programs for reducing pollution
Tier 1

29 Government programs for reducing pollution:
For sustainable development, governmental pollution prevention programs can best counteract the pressure to invest in “end of pipe” pollution solutions by demonstrating the economic and environmental benefits of a source reduction approach, making technical information available and providing technical assistance. EPA has been working with industry and government representing environmental, community and work force issues to prevent pollution at the source prior to “end of pipe” treatment. (Shen,1999) NEPA: National Environmental Pollution Act. TCSA: Toxic Substance Control Act. CAAA: Clean Air Act Amendment. PPA: Pollution Prevention Act. ************************************** Sustainable:"Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs." Sustainable development focuses on improving the quality of life for all of the Earth's citizens without increasing the use of natural resources beyond the capacity of the environment to supply them indefinitely. Sustainable development of water resources requires that we respect the hydrologic cycle by using renewable water resources that are not diminished over the long term by that use. Tier 1

30 Government programs for reducing pollution:
Laws such as NEPA, TCSA, CAAA and PPA remain outside the scope of most pollution control work. The following options were suggested for USEPA for moving forward interaction in the US: Add multi-media provisions to the existing regulations. Correct laws in other policy sectors with environmental measures. Make NEPA a stronger statute. Make TSCA a law which can use EPA programs to control and reduce toxic substances. Establish pollution prevention approaches. Tier 1

31 Programs for reducing pollution:
Manufacturers could implement a variety of improved management procedures that would aid pollution reduction: Environmental audits. Identify (inventory) and correct problems (strategies to achieve reductions) that generate wastes. Regular preventive maintenance. Inspection, maintenance and replacement of equipment. Material handling and storage. Emissions of hazardous material must be avoided. There should be labels of all containers and first aid recommendations. Employee training. Well informed employees are better able to make valuable waste reduction suggestion. Operating manual and record keeping. Good facility documentation: process procedures, control parameters, hazards and operator responsibilities. Tier 1

32 Environmental programs:
Some industries may see no difference between end of pipe pollution control and a front end pollution prevention control. The importance is that those industries may not go beyond the first stage of waste reduction. As the environmental concern deepens, industries have to move further up the production chain: End of pipe solution to wastes and pollutants; and later Internal process modifications to reduce emissions and wastes, and eventually Redesign products to achieve a maximum level of recycling of raw materials and minimization of wastes after the products are used. (Shen, 1999) pp 252. Tier 1

33 Some measurements to save water:
Keep water effluent streams separated. Reuse water as close to source as possible. Recycling whenever it is possible. Better control of usage with automated systems. Checking and control of leaks. When buying new equipment, evaluate water-efficiency models including accessories. Reducing the quantities of chemicals so that the amount of dilution water will be reduced. Tier 1

34 Reusing water: It is not only possible but necessary to reuse wastewater of a process stream before it leaves the plant accomplished by piping, diluting or treating some of the effluents before using them again. Some plants are now using closed systems, so that there are no water discharges. Zero discharges has been practiced in locations where water is scarce, and may involve technologies for removing suspended and dissolved solids. Complete demineralization is relatively expensive, however, in some cases wastewater discharges can be reduced significantly with other less expensive technologies. Incentives for water reuse involve the possibilities of reduction of wastewater treatment costs and raw water costs (J.N.Tanis, 1987). (Higgins, 1995). Tier 1

35 Treatment processes Tier 1

36 Expectations of a water treatment program:
The expectations from a water treatment program should be integrated to include all aspects of the program, from the proposal through to the implementation stages. Tier 1

37 Treatment Program As we will see in the next diagram, the expectations that a good treatment program should give us are listed below: Overview of a new or existent problem. Lab study of all system and water composition. Submit a proposal. Program implementation. Monitoring to optimize. Use of modern treatment techniques. In the first step, the vendor must study the parameters of all the system and the chemical composition of the water , then with the aid of lab study, the vendor must be able to submit a proposal to treat the system. When the operating plan is satisfied with the economical and technical plan, the proposal is accepted and the program is now implemented. Next important step is constantly monitoring to optimize the program. Lastly, the vendor should make an effort to use the most modern treatments in the program whenever they offer technical or economical advantages. When all of this mentioned is applied properly, the system is under control, that is, production and equipment is maximized with the minimum of pollutants (J.N.Tanis, 1987). Program under control Tier 1

38 Treatment Program New or Problem System Plant Study Proposal System
Implement Program System under control Lab Study Follow-up New Product Technology Tier 1

39 Wastewater treatment processes:
Wastes are generated by every industrial enterprise, and this wastes can either be liquids or solids. Wastewater treatment can be divided into three stages: Primary treatment that uses physical operations to remove free oil and/or suspended solids. Secondary treatment to remove dissolved contaminants through chemical or biological action, and Tertiary treatment for the removal of residual contaminants. (Allen, 1997) Tier 1

40 Separation order This list shows how separation is carried out:
Primary treatment Sedimentation Aeration Secondary treatment Tertiary treatment Tier 1

41 Treatments… Primary treatment prepares the wastewater for biological treatment. Large solids are removed by screening, and grit. Equalization in a mixing basin, levels out the flows variation and concentrations. Neutralization, where required, follows equalization. Oils, greases and suspended solids are removed by flotation, sedimentation of filtration. Secondary treatment is a biological degradation of soluble organic compounds from input levels of mg/l BOD or greater to effluent levels under 15 mg/l. Aerobic treatment in an open vessel is done. After biotreatment, the microorganisms and solids suspended are allowed to settle. Tier 1

42 Treatments… The tertiary treatment remove specific residuals. By filtration, suspended colloidal solids can be removed; adsorption removes organics by granular activated carbon (GAC); and chemical oxidation also removes organic compounds. Tertiary systems have to treat great amounts of wastewater, so they are expensive. When streams rich in heavy metals, pesticides or other substances that may pass through primary treatment and inhibit biological treatment are present, in-plant treatments are necessary. Precipitation, activated carbon adsorption, chemical oxidation, air or steam stripping, wet air oxidation, ion exchange, reverse osmosis are some of the methods useful when in-plant treatments are to be used. Tier 1

43 The tertiary treatment…
Tertiary treatment is a polishing step. Its importance is that rather than have to find solutions at the end of pipe, where primary and secondary treatments are used to, it is possible to minimize some toxics or hazardous components in the process before they are combined with other less “hazardous”. Biological treatment usually produces a ’30/20’ effluent with no more than 30 mg/l suspended solids and 20 mg/l BOD. Tier 1

44 Tertiary treatment However, river flows have decreased owing to drought conditions. In these circumstances, new limits are imposed on the quality of the final effluent. The treatment processes beyond the secondary treatment to achieve the required limits in the process are well known as tertiary treatments. Tier 1

45 In plant treatment Before end of pipe wastewater treatment, a program of waste minimization should be initiated. Recirculation. In the paper board industry, white water from a paper machine can be put through a save all to remove the pulp and fiber and recycled to various points in the process. Segregation. Clean streams are separated for direct discharge. Disposal. In many cases, the total discharge BOD and suspended solids can be reduced by removal of residue in semidry state for disposal. Reduction. The use of automatic cutoffs can reduce the wastewater volume. Substitution. The substitution of chemical additives of a lower pollutional effect in processing operations. (Eckenfelder, 2000) pp34 Tier 1

46 Wastewater treatment processes: Process selection
. Tier 1

47 Figure 1. Conceptual treatment program for organic and toxic industrial wastewater
For wastewaters containing nontoxic organics, process design criteria can be obtained from lab studies. To define the wastewater treatment problems, a preliminary analysis should be carried out: Organic streams Streams containing heavy metals Mineral streams volatile Toxic and/or nonbiodegradable Biodegradable Source control Figure 3. (Eckenfelder, 2000). The objective of equalization is to minimize or control fluctuations in wastewater characteristics to provide optimum conditions for subsequent treatment processes. Many industrial wastes contain alkaline materials that require neutralization prior to discharge or prior to chemical or biological treatment. Equalization Neutralization Oil/grease removal Suspended solids Biological treatment Final disposal Tier 1 (Eckenfelder, 2000)

48 Source treatment: goal
Source reduction is any activity that reduces or eliminates the generation of hazardous wastes at the source The fundamental goal is to enact changes in consumption, use and waste generation patterns associated with products (Higgins, 1995). pp. 421, 93. Tier 1

49 Source treatment: Source treatments involves different definitions of source reduction, but the general consensus appears to be that include any in-plant actions to reduce the quantity or the toxicity of the waste at the source. Examples include equipment modification, design and operations changes of the process and products and substitution of raw materials. Tier 1

50 Figure 2. Laboratory studies for heavy metals/volatile organics
start VOC/NH3 Air or steam stripping Equalized sample Priority pollutants scan and bioassay Chemical oxidation reduction Precipitation Heavy metals When toxic and nontoxic organics and inorganics are present, it is necessary to evaluate the existence of heavy metals or volatile organics. Fed batch reactor Nondegradable/ toxic Source treatment Degradable (Eckenfelder, 2000) Source treatment: Source treatment technologies are shown in Figure 3. TDS: total dissolved solids. It is necessary to determine whether the wastewater is biodegradable and whether it will be toxic to the biological process at some level of concentrations. The fed batch reactor is employed for this purpose. If the wastewater is biodegradable, it is subjected to a long term biodegradation to remove all degradable organics. The next step is to evaluate priority pollutants. If priority pollutants have not been removed, it should be considered for source treatment or tertiary treatment with activated carbon Long-term biodegradation Granular activated carbon Reverse osmosis Priority pollutants scan and bioassay Powder activated carbon Priority pollutants/toxic Ion exchange TDS/inorganics Tier 1 (Eckenfelder, 2000)

51 Figure 3. Treatment of toxic wastewater: In-plant treatment
To discharge recycle or treatment Reverse osmosis If the wastewater is nonbiodegradable or toxic, it should be considered source treatment or in-plant modification. Ion exchange Polymeric resins Granular carbon adsorption Filtration Anaerobic treatment (Eckenfelder, 2000) In-plant treatment is necessary for streams rich in heavy metals, pesticides and other substances that would pass through primary treatment and inhibit biological treatment. In-plant treatment also makes sense for low-volume streams rich in nondegradable materials, because it is easier and cheaper to remove a specific pollutant from a small, concentrated stream than from a large, dilute one. Precipitation Oxidation reduction Wet air oxidation Air or steam stripping Chemical oxidation Volatile organics ammonia Process wastewater Heavy metals Organic chemicals Tier 1 (Eckenfelder, 2000)

52 Methods for suspended solids removal
Sedimentation is the more common technique in wastewater treatment because it involves little mechanical equipment and it is very stable to operate. However, there are some situations where flotation is a better choice. Flotation is a good technique for solids removal when the density difference between water and the solids is marginal, or the solids have a high fat or oil content. (Arundel, 2000). Tier 1

53 Methods for suspended solids removal
Coagulation is employed for removal of waste materials in suspended or colloidal form. Colloids are particles within the size range of 1 nm to 0.1 nm, do not settle out on standing and can not be removed by conventional physical treatment processes. Precipitation. In the water treatment, the precipitation process is used for softening (removal of the hardness caused by calcium and magnesium) and removal of iron and manganese. (Qasim, 2000). (Eckenfelder, 2000) Tier 1

54 Sedimentation: Reduce solids by at least 50%, with proportional reduce of BOD. Addition of chemicals to assist settlement by coagulating particles or chemical precipitation can be essential. Can have acceptable discharge standards with regular desludging without a secondary treatment. Primary tanks are desludged at intervals of between 8 and 24 hours. Secondary settlement follows any form of biological aeration or filtration to produce an effluent low in solids. Particularly demanding discharge consents may dictate a tertiary treatment to remove solids and BOD by a further 50%. These intervals between 8 and 24 hours desludging, avoid odor problems and rising sludge (Arundel, 2000). Tier 1

55 Flotation: Dissolved air flotation, which is a common technique. This technique basically consists on injecting an aqueous stream containing dissolved air into the wastewater . The dissolved air forms bubbles when it comes out of solution and carries suspended particles, which tend to concentrate at the bubble wastewater interface, to the surface, where they form an emulsion. (Allen, 1997). Tier 1

56 Flotation: General diagram for flotation methods: Tier 1

57 Coagulation: Paperboards wastes can be effectively coagulated with low dosages of alum. Silica or polyelectrolyte will aid in the formation of a rapid settling floc. Wastes that contain emulsified oil can also be clarified by coagulation. For effective coagulation, alkalinity should first be added, . After addition of alkali and coagulant, a rapid mixing is recommended. (Eckenfelder, 2000). Tier 1

58 Precipitation: Chemical precipitation in wastewater treatment involves the addition of chemicals to alter the physical and chemical state of dissolved and suspended material and to facilitate their removal. It is usually combined with coagulation, flocculation, separation. Principle: Dissolved compounds, for instance heavy metal ions, are brought into their insoluble hydroxides by pH increase through dosing of lime or NaOH. Using coagulation, flocculation techniques these small hydroxide nuclei become larger flocs for separation. With proper precipitants these flocs also serve as entrapment for other dissolved (organic) compounds; a form of co-precipitation. Chemical precipitation Chemical precipitation in wastewater treatment involves the addition of chemicals to alter the physical and chemical state of dissolved and suspended material and to facilitate their removal. It is usually combined with coagulation – flocculation – separation. Principle Dissolved compounds, for instance heavy metal ions, are brought into their insoluble hydroxides by pH increase through dosing of lime or NaOH. Using coagulation, flocculation techniques these small hydroxide nuclei become larger flocs for separation. With proper precipitants these flocs also serve as entrapment for other dissolved (organic) compounds ; a form of co-precipitation. Chemical precipitation Chemical precipitation in wastewater treatment involves the addition of chemicals to alter the physical and chemical state of dissolved and suspended material and to facilitate their removal. It is usually combined with coagulation – flocculation – separation. Principle Dissolved compounds, for instance heavy metal ions, are brought into their insoluble hydroxides by pH increase through dosing of lime or NaOH. Using coagulation, flocculation techniques these small hydroxide nuclei become larger flocs for separation. With proper precipitants these flocs also serve as entrapment for other dissolved (organic) compounds ; a form of co-precipitation. Tier 1

Conventional precipitation Hydroxide Sulfide carbonate coprecipitation Enhanced precipitation Dimethyl thio carbamate Diethyl thio carbamate Trimercapto-s-triazine, trisodium salt Other methods Ion exchange Adsorption Recovery opportunities Membranes Electrolytic techniques (Eckenfelder, 2000) pp 138 Tier 1

60 The Biological Treatment
When biological treatment is needed, there are several options: Influent wastewater High strength Physical and chemical treatment No Yes High strength Yes Anaerobic treatment Biodegradable Yes Polished effluent Yes Inhibitory Nondegradable fraction No Discharge PACT No Discharge PACT is the process adding powered activated carbon. (Eckenfelder, 2000). Complete mix system No Readily degradable No Nitrogen No Dispersed growth system removal required Fixed Growth system Yes Yes Plug flow system Selector system Intermittent process Nitrification/ Denitrification system Yes Polished effluent No Discharge Discharge Tier 1 (Eckenfelder, 2000)

61 The biological treatment: typical operating parameters and dimensions
Treatment method Mode of operation Degree of treatment Land requirements Equipment Remarks Lagoon Intermittent or continuous discharge; facultative or anaerobic Intermediate Earth dug; days’ retention Odor control frequently required Activated lagoons Completely mixed or facultative continuous basins High in summer; less in winter Earth basin, 8-16 ft deep, 8-16 acres/(million gal/d) Pier-mounted or floating surface aerators or subsurface diffusers Solids separation in lagoon; periodic dewatering and sludge removal Activated sludge Completely mixed or plug flow; sludge recycle > 90% removal of organics Earth or concrete basin; 12p20 ft deep; ft3/(million gal/d) Diffused or mechanical aerators; clarifier for sludge separation and recycle Excess sludge dewatered and disposed of Trickling filter Continuous application; may employ effluent recycle Intermediate or high, depending on loading ft /(million gal/d) Plastic packing ft deep Pretreatment before POTW or activated sludge plant RBC Multistage continuous Intermediate or high Plastic disks Solids separation required Anaerobic Complete mix with recycle; upflow or downflow filter, fluidized bed; upflow sludge blanket Gas collection required; pretreatment before POTW or activated sludge plant Spray irrigation Intermittent application of waste Complete; water percolation into groundwater and runoff to stream gal/(min.acre) Aluminum irrigation pipe and spray nozzles; movable for relocation Solids separation required; salt content in waste limited (Eckenfelder, 2000). POTW: Primary and secondary treatment processes handle most of nontoxic wastewaters; other waters have to be pretreated before being added to this flow Tier 1 (Eckenfelder, 2000)

62 Advanced wastewater treatments
Advanced wastewater treatment is defined as the processes that remove more pollutants from wastewater than the conventional treatments. This term may be applied usually as tertiary treatment, but most of their goals are to remove nitrogen, phosphorus, and suspended solids. Advanced treatments include: Chemical coagulation of wastewater Granular media filters Ultrafiltration Nanofiltration Wedge-wire screens Microscreening Diatomaceous earth filters (Shun Dar Lin, 2001) pp. 522 Tier 1

63 Volume and disposal reduction
Tier 1

64 Volume reduction Volume reduction can be used to reduce treatment cost and to reduce handling and disposal costs for residues remaining after treatment. Volume reduction can be accomplished by using a variety of methods: Reuse of treated wastewater and wastes Treatment modifications to reduce solid residues Segregated treatments to reduce hazardous waste mixtures Incineration to reduce waste volume and to render a hazardous waste nonhazardous. (Higgins, 1995). Tier 1

65 Reduction of waste production and disposal volumes
Simple dewatering: the sludge is discharged into a series of tanks and allowed to settle. Top water can then be decanted. This method reduce the volume of sludge for disposal. Composting: the material is mechanically turned at intervals, force aerated and often contained in a building where heat losses, odor and water content can be controlled. (Arundel, 2000) pp 113 Tier 1

66 Reduction of waste production and disposal volumes
Digestion: is the slow degeneration of the organic content of sludge by obligate anaerobic bacteria to simpler compounds- carbon dioxide, water and anions (nitrate, sulphate, phosphate). Digestion is one of the few sludge treatment processes in which a significant reduction of pathogens is possible. The digestor gas produced is 65-70% methane, 30-34% carbon dioxide, and traces of sulphur compounds. The collected gas is burnt in a boiler to keep the digestor warm and the excess put to further heating or power generation purposes. Tier 1

67 Reduction of waste production and disposal volumes
Incineration: its main advantages lie in the complete destruction of organic compounds, the ash being inert and usually less than 25% of the original sludge volume. Most incinerators are of the fluidized bed variety. Tier 1

68 A waste management diagram…
Upgrade operation Waste recycle Redesign process Waste treatment Increasing Effectiveness of waste management Industrial wastes can be classified into organic or inorganic, and hazardous or non hazardous. (Shen, 1999). Substitute raw material Waste disposal Tier 1

69 Multiple choice questions
Tier 1

70 Tier 1: Quiz 1. What is pollution?
Pollution refers to harmful environmental contaminants and to the act or process of polluting the environment. Any undesirable change in the characteristics of the air, water, soil or food that can affect the health called pollution. Unwanted chemicals or other materials found in the environment. Pollutants can harm human health, the environment, and property. All of the above. Tier 1

71 Tier 1: Quiz 2. What is BOD? The quantity of oxygen required for the stabilization of the oxidizable organic matter present over 7 days of incubation at 20 oF. An empirical test used for measuring waste, evaluating the measure of the oxygen required by microbes to degrade a sample of effluent. A test used to evaluate the quantity of oxygen present in the stream. The quantity of oxygen required to develop a biochemical test. Tier 1

72 Tier 1: Quiz 3. Why is it important to reduce hazardous contaminants?
Because if discharged, they can lead to water pollution. Because of its radioactive characteristics, its effects on human health and development of cancer. Communicable diseases can be transmitted when in contact to them. Because of their dangerous characteristics for human health and the environment. Tier 1

73 Tier 1: Quiz Tier 1


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