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الكلية كلية الهندسة     القسم  الهندسة البيئية     المرحلة 4
أستاذ المادة محمد عبد مسلم عبد الله الطفيلي       31/01/2018 16:36:51
SECTION -1
WASTEWATER ENGINEERING
(AN OVERVIEW)

INTRODUCTION
Every community produces both liquid and solid wastes and air emissions. The liquid wastewater is essentially the water supply of the community after it has been used in a variety of applications (see Fig. A-1). Wastewater may be defined as a combination of the liquid or water - carried wastes removed from residence, institutions, and commercial and industrial establishments, together with such ground water, surface water, and storm water as may be present.
DEFINITION OF WASTEWATER ENGINEERING

Wastewater engineering is that branch of environmental engineering in which the basic principles of science and engineering are applied to solving the issues associated with the treatment and reuse of wastewater. The ultimate goal of wastewater engineering is the protection of public health in a manner commensurate with environmental, economic, social, and political concerns.
SEWERAGE:
Sewerage refers to the collection of wastewater from occupied areas and conveying them to some point of disposal. The liquid waste usually, will require treatment before they can be discharged into a body of water or so as not to endanger the public health or causing offensive conditions. Sewerage (Sewage) works include all the physical structures required for that collection, treatment and disposal.
SEWAGE
Sewage is the liquid waste conveyed by a sewer and may include domestic and industrial discharges as well as storm sewage, infiltration and inflow.
SEWER
A sewer is a pipe or conduit, generally closed, but normally no flowing full, which carries sewage.
WASTEWATER SOURCES AND FLOW RATES
A fundamental prerequisite to begin the design of wastewater facilities is a determination of the design capacity. This, in turn, is a function of the wastewater flow rates. The determination of wastewater flow rates consists of five parts: (1) selection of a design period, (2) estimation of the population and commercial and industrial growth, (3) estimation of wastewater flows, (4) estimation of infiltration and inflow, and (5) estimation of the variability of the wastewater flow rates.
DESIGN PERIOD
The design period (also called the design life ) is not the same as the life expectancy. The design period is the length of time it is estimated that the facility will be able to meet the demand, that is, the design capacity. The life expectancy of a facility or piece of equipment is determined by wear and tear. Typical life expectancies for equipment range from 10 to 20 years. Buildings, other structures, and pipelines are assumed to have a useful life of 50 years or more. Design periods that are commonly employed in practice and commonly experienced life expectancies are shown in Table A-1 .
TABLE A-1
DESIGN PERIODS FOR WASTEWATER WORKS





































FIGURE A-1

SCHEMATIC DIAGRAM OF A WASTEWATER MANAGEMENT INFRASTRUCTURE
SECTION -2
CHARACTERISTICS OF WASTEWATER

Sewage is the wastewater of a community. It may be purely domestic or may contain some industrial or agricultural wastewater. Domestic sewage composed of human body wastes. (faeces and urine) and sullage which is the wastewater resulting from personal washing,, laundry, food preparation and the cleaning of kitchen utensils. Sewage consist of about 99.9% water and 0.1 % solids, the solids are either organic or inorganic. The organic solids consist of about 65% protein, 25% carbohydrate and 10% fats.
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Wastewater quality can be defined by
1. Physical characteristics.
2. Chemical characteristics.
3. Biological characteristics.

PHYSICAL PARAMETERS
Physical parameters include color, odor, temperature,solids (residues), turbidity, oil, and grease. Solids can be further classified into suspended and dissolved solids (size and settleability) as well as organic (volatile) and inorganic (fixed) fractions.
CHEMICAL PARAMETERS
Chemical parameters associated with the organic and Inorganic content. Organic content parameters of wastewater include the biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), and total oxygen demand (TOD). Inorganic content parameters of wastewater include salinity, hardness, pH, acidity, alkalinity, iron, manganese, chlorides, sulfates, sulfides, heavy metals (mercury, lead, chromium, copper, and zinc), nitrogen (organic, ammonia, nitrite, and nitrate), and phosphorus.
BACTERIOLOGICAL PARAMETERS
Bacteriological parameters include coliforms, fecal coliforms, specific pathogens, and viruses. Design considerations for wastewater treatment facilities are based in part on the characteristics of the wastewater.
SUMMARY OF WASTEWATER CHARACTERISTICS

• Table A-2 shows the typical concentration range of various constituents in untreated domestic wastewater. Depending on the concentrations, wastewater is classified as strong, medium, or weak.
• The types and numbers of microorganisms in untreated domestic wastewater vary widely; examples of such variations are shown in Table A-3.
• Table A-4 shows typical mineral increases resulting from domestic water use.
• Table A-5, shows particle sizes related to different categories.
• Odors in wastewater are caused by gases from decomposition or by odorous substances within the wastewater. Table A-6 lists examples of odorous compounds associated with untreated wastewater.
• Organic matter in wastewater can be related to oxygen demand and organic carbon measurements.
• Table A-7 shows several measures of organic matter.
• Wastewater contains a variety of solid materials varying from rags to colloidal material. In the characterization of wastewater, coarse materials are usually removed before the sample is analyzed for solids. The various solid classifications are identified in Table A-8 .










TABLE A-2
TYPICAL COMPOSITION OF UNTREATED DOMESTIC WASTEWATER


















TABLE A -3
TYPES AND NUMBER OF MICROORGANISMS TYPICALLY FOUND IN UNTREATED DOMESTIC WASTEWATER










TABLE A -4
TYPICAL MINERAL INCREASE FROM DOMESTIC WASTEWATER















TABLE A-5
GENERAL CLASSIFICATION OF WASTEWATER SOLIDS















TABLE A-6
ODOROUS COMPOUNDS ASSOCIATED WITH UNTREATED WASTEWATER










TABLE A-7
OXYGEN DEMAND AND ORGANIC CARBON PARAMETERS

















TABLE A-8
DEFINITIONS FOR SOLIDS FOUND IN WASTEWATER
Test Describtion
Total solids (TS) The residue remaining after a wastewater sample has been evaporated and dried at a specified temperature (103 to 105°C)
Total volatile solids (TVS) Those solids that can be volatilized and burned off when the TS are ignited (500 ±50°C)
Total fixed solids (TFS) The residue that remains after TS are ignited
(500 ±50°C)
Total suspended solids (TSS)
Portion of the TS retained on a filter with a specified pore size, measured after being dried at a specified temperature (105°C). The filter used most commonly for the determination of TSS is the Whatman glass fiber filter, which has o nominal
pore size of about 1.58 µm
Volatile suspended solids (VSS) Those solids that con be volatilized and burned off when the TSS are ignited (500 ±50°C)

Fixed suspended solids I FSS) The residue that remains after TSS ore ignited (500 ±50°C)

Total dissolved solids (TDS)
(TS - TSS)
Those solids that pass through the filter, and ore then evaporated and dried at specified temperature. It should be noted that what is measured as TDS is comprised of colloidal and dissolved solids. Colloids are typically in the size range from 0.001 to 1 µm
Total volatile dissolved solids (VDS) Those solids that con be volatilized and burned off when the IDS ore ignited (500 ±50°C)
Fixed dissolved solids (FDS) The residue that remains after TDS ore ignited (500 ±50°C)
Settleable solids
Suspended solids, expressed as milliliters per liter, that will settle out of suspens1on w1thm a specified period of time












SECTION -3
ANALYSIS AND SELECTION OF WASTEWATER FLOW RATES AND CONSTITUENT LOADINGS

Reliable data for existing and projected flow rates affect the hydraulic characteristics, sizing, and operational considerations of the treatment system components. Constituent mass loading, the product of constituent concentration and flow rates are necessary to determine the capacity and operational characteristics of the treatment facilities and ancillary equipment to ensure that treatment objectives are met.

WASTEWATER SOURCES AND FLOW RATES
Data that can be used to estimate average wastewater flow rates from various sources include:
1. Domestic sources
• residential areas
• commercial districts
• institutional
• recreational facilities
2. Industrial sources
3. Infiltration/Inflow contribution
? DOMESTIC WASTEWATER SOURCES AND FLOW RATES
The principal sources of domestic wastewater in a community include:
1. residential areas
2. commercial districts
3. institutional
4. recreational facilities
Water consumption records may be used for estimating flow rates. The average about 60 to 90 percent of the per capita of water consumption becomes wastewater.
? RESIDENTIAL AREAS.
For many residential areas, wastewater flow rates are commonly determined on population and the average per capita contribution of wastewater. See Table A-9









TABLE A-9
TYPICAL WASTEWATER FLOW RATES FROM URBAN RESIDENTIAL












? COMMERCIAL DISTRICTS

Depending on the function and activity, unit flow rates for commercial facilities can vary widely. Because of the wide variations that have been observed, every effort should be made to obtain records from actual or similar facilities. If no other records are available, estimates for selected commercial sources based on function or persons served, may be made using the data presented in Table A-10. Flow rates were generally expressed in terms of quantity of flow per unit area ( i.e.. m3/ha.d ). Typical unit-flow rate allowances for commercial developments normally range from 7.5 to l4 m3/ha.d .

? INSTITUTIONAL FACILITIES

Typical flow rates from some institutional facilities are shown in Table A-11. It is stressed that flow rates vary with the region, climate, and type of facility. The actual records of institutions are the best sources of flow data for design purposes.

? RECREATIONAL FACILITIES

Wastewater flow rates from many recreational facilities are subject to seasonal variations. Typical data on wastewater flow rates from recreational facilities are presented in Table A-12.

TABLE A-10
TYPICAL WASTEWATER FLOW RATES FROM COMMERCIAL SOURCES























































TABLE A-11
TYPICAL WASTEWATER FLOW RATES FROM INSTITUTIONAL SOURCES




































TABLE A-12
TYPICAL WASTEWATER FLOW RATES FROM RECREATIONAL FACILITIES






























SELECTION OF DESIGN FLOW RATES
• A yardstick by which total dry weather base flow can be measured is 460 L/capita.d. The base flow includes 270 L/capita.d for domestic flows, 40 L/capita.d for commercial and small industrial flows, and 150 L/capita.d for infiltration.
• In the absence of measured flow rate data, minimum daily flow rates may be assumed to range from 30 to 70 percent of average flow rates for medium to large size communities.
STRATEGIES FOR REDUCING INTERIOR WATER USE AND WASTEWATER FLOW RATES

Because of the importance of conserving both resources and energy, various means for reducing wastewater flow rates and pollutant loadings from domestic sources are available. The reduction of wastewater flow rates from domestic sources results directly from the reduction in interior water use.
• Representative water use rates for various devices and appliances are reported in Table A-13.
• Information on the relative distribution of water use within a residence is reported in Table A-14.
• Devices and appliances that can be used to reduce interior domestic water use and wastewater flows are described in Table A-15.
TABLE A-13
TYPICAL RATES OF WATER USE FOR VARIOUS DEVICES AND APPLIANCES














TABLE A-14
TYPICAL DISTRIBUTION OF RESIDENTIAL INTERIOR WATER USE


























TABLE A-15
FLOW-REDUCTION DEVICES AND APPLIANCES





















• A comparison of residential interior water use (and resulting per capita wastewater flows), from a recent survey, is given in Table A-16 for homes without and with water-conserving fixture.




TABLE A-16
TYPICAL COMPARISONS OF INTERIOR WATER USE WITHOUT AND WITH WATER-CONSERVATION PRACTICES END DEVICES

























EXAMPLE
A new subdivision of 2000 home is planned, and a condition of the building permit is to determine the savings in water consumption (and wastewater flows) if the following water-efficient appliances are used:

1. Front-loading. washing machine
2. Ultra-low flush toilets
3. Ultra-low-flow showerhead
Use 3.5 residents per home and values for devices and appliances from Table A-16.
SOLUTION
The estimated water use and percentage savings are illustrated in the following table.


المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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