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TYPES AND CHARACTERISTICS OF WASTEWATER
Classifications of Waste Water
Domestic waste waters
These waters areproduced by the mere actsof living such as using thebathroom, doing laundry,or washing the dishes.
Classifications of Waste Water
Process waste waters
These waters are producedby some industrial processesand include the undesiredliquid product of any unitoperation. The majorconcern with these wastes isthe reactions that may occurwith the environment beingeither direct or indirect.Some may rob oxygen fromthe environment, whileothers may be toxic
Industrial Water Pollution
Industrial pollutants that run into streams, rivers, or lakescan have serious effects on wildlife, plants, and humans. Inthe United States there are strict rules for the amount andcomposition of substances that factories can release intobodies of water. These rules are not always enforced, andmuch industrial water pollution comes from accidentalchemical or oil spills.
Industrial Wastes
Cooling waste waters
These are produced as a resultof heat exchanger where heatis removed from the product.Waters can be used once orrecycled.. This type of wastemust also be monitored andoften treated, and is also amajor factor in thermalpollution of water sources.
Thermal Pollution from Power Plants and FactoriesPower plants and industrial factories are among the major contributorsto the problem of thermal pollution. These facilities draw water fromnearby lakes and streams, which they use to cool their machinery andsteam-driven equipment. The heated water warms local bodies ofwater by as much as 10° C (18° F), making the water uninhabitablefor fish and other organisms.
THERMAL POLLUTION
CHARATERISTICS of Wastewater
PHYSICAL CHARACTERISTICS
•Temperature•Wide variation in the wastewater temperature indicatesheated or cooled discharges.
•decreased temperatures after a snowmelt or rainfall mayindicate serious infiltration.
•Changes in wastewater temperatures affect the settling rates,dissolved oxygen levels, and biological action.
•The temperature of wastewater becomes extremelyimportant in certain wastewater unit operations such assedimentation tanks and recirculating filters.
Color
The color of wastewater containing dissolved oxygen (DO) isnormally gray. Black-colored wastewater usually accompaniedby foul odors, containing little or no DO, is said to be septic.
Significance of Color in Wastewater
oil wastesdomestic wastes
White color of the chemical wastes
Though the colors are beautiful, it is full of chemical
wastes.
No one is sure exactly how the ocean will disperse pollutants, such as dioxin, from
the mill
Processing timber into pulp at the mill will result in tons of effluent a day being discharged
OdorDomestic sewage should have a musty odor. Bubbling gas and/orfoul odor may indicate industrial wastes, anaerobic (septic)conditions, and operational problems.
Odors in Wastewater Treatment Plant
SolidsWastewater is normally 99.9 % water and 0.1 % solids. If awastewater sample is evaporated, the solids remaining are totalsolids.
Types Solids:
1. Dissolved solids is an expression for the combinedcontent of all inorganic and organic substancescontained in a liquid which are present in amolecular, ionized or micro-granular suspendedform.
Dissolved solids pass through a fine mesh filter. Normal wastewater processes using settling or flotation are designed to remove solids but cannot remove dissolved solids. -
Taste/Health: High TDS results in undesirable taste whichcould be salty, bitter, or metallic. It could also indicate thepresence of toxic minerals. The EPA's recommendedmaximum of TDS in water is 500mg/L (500ppm).
Filter performance : Test your water to make sure the filtersystem has a high rejection rate and know when to changeyour filter (or membrane) cartridges.
Hardness: High TDS indicates Hard water, which causes scale buildup in pipes and valves, inhibiting performance.
Aquaculture: A constant level ofminerals is necessary for aquatic life.The water in an aquarium should havethe same levels of TDS and pH as thefish and reef's original habitat.
Hydroponics: TDS is the bestmeasurement of the nutrientconcentration in ahydroponics' solution.
Nutrients for hydrophonics
Pools and Spas: TDS levels must be monitored to prevent maintenance problems.
Commercial/Industrial/Medical: High TDS levelscould impede thefunctions of certainapplications generators
Dialysis machine
2. Suspended -
3. Settleable
This parameter was at one time called non-filterable residue (NFR), a term that refers tothe identical measurement: the dry-weight ofparticles trapped by a filter, typically of aspecified pore size.
or settleable, solids will settle out of waterover time, though this may be so slow that it isimpractical to allow the particles to settle outin a water treatment plant. The particles aremore than 1,000 Mu in size and can be seenwith a microscope or, sometimes, with thenaked eye. Ex. of sand and heavy silts.
4. Floatable Solids
5. Colloidal Solids
Floatables discharged to receiving waters create avariety of problems. Visible, floating materialdegrades the aesthetics of waterways and theirshorelines, which in turn can contribute to loss ofuse (e.g. beach closings) and can have an adverseeconomic impact on recreation and business inthe area.
also known as nonsettleable solids, do not dissolve inwater although they are electrically charged, the particlesare so small that they will not settle out of the water evenafter several years and they cannot be removed byfiltration alone, can be seen only with a high-poweredmicroscope. Ex. bacteria, fine clays, and silts. Colloidalsolids often cause colored water, such as the "tea color"of swamp water.
6. Organic Solids
7. Inorganic solids
Volatile suspended solids reflects the weightof organic matter in the dried solids thatburns off after combustion at 550 degrees Cand indicates the organic solids content ofthe water sample.
Non-volatile suspended solids reflects theweight of solids remaining on the filter aftercombustion and indicates the inorganicsolids (primarily sediment) content of thewater sample.
CHEMICAL CHARACTERISTICS
pH The term pH is used to describe the acid or baseproperties of water solutions.
A pH value less than 7 in the wastewater plant influentmay indicate septic conditions of wastewater.
Pretreatment of these wastes at the source is usuallyrequired since extreme pH values may damagebiological treatment units.
The pH values less than 5 and more than 10 usuallyindicate that industrial wastes exist and are notcompatible with biological wastewater operations.
Common Substances’ pH Values
Dissolved oxygen
Dissolved oxygen (DO) in wastewater has a great effect on the characteristics of the water.
Wastewater that has DO is called aerobic or fresh. Aerobic raw sewage is usually gray in color and has a musty odor.
Wastewater that has noDO is called anaerobic orseptic. Anaerobic rawsewage is usually blackand has an offensivehydrogen sulfide or rottenegg odor.
Aerobic sludge foam
Anaerobic digester
Oxygen demand is the amount of oxygen used by bacteria andother wastewater organisms as they feed upon the organicsolids in the wastewater.
Sludge deposits, odors, and fish kills may occur if removal is not adequate.
Chemical tests such as the BOD (biochemical oxygen demand),the COD (chemical oxygen demand), the ODI (instantaneousoxygen demand or oxygen demand index), and the TOC (totalorganic carbon) measure the "strength" of sewage. It isimportant that organic wastes be removed to protect thereceiving body of water into which the wastewater plant isdischarging.
Nutrients
Removal is accomplished by processes in addition to normal wastewater treatment or tertiary treatment, when specific reuse requirements require it.
Nutrients are life-supporting nitrogen and phosphorus.
They stimulate excessive growths of algae and other aquaticplant life. They are always present in domestic wastewatersand are not removed during conventional primary andsecondary treatment.
BIOLOGICAL CHARACTERISTICS
Bacteria
Fecal coliform counts of 100 million per 100 milliliters may befound in raw domestic sewage. Detectable health effects havebeen found at levels of 2,300 to 2,400 total coliforms per 100milliliters in recreational waters.
pathogenic (disease-causing) organisms such astyphoid, dysentery, and other intestinaldisorders may be present in wastewater.
Tests for total coliform and fecal coliform nonpathogenicbacteria are used to indicate the presence of pathogenicbacteria. Because it is easier to test for coliforms, fecalcoliform testing has been accepted as the best indicator offecal contamination.
Disinfection, usually chlorination, is generally used to reducethese pathogens. Breakdown or malfunctions of chlorinationequipment will probably result in excessive discharge ofpathogenic organisms and can seriously affect public health.
Bacteria can also be classified according to their dissolvedoxygen requirement. Aerobic bacteria are bacteria thatrequire dissolved oxygen to live. Anaerobic bacteria cannotlive if dissolved oxygen is present. Facultative bacteria canlive with or without dissolved oxygen.
Viruses Wastewater often contains viruses that may producediseases. Outbreaks of infectious hepatitis havebeen traced through water systems because ofwastewater entering the supply. sedimentation,filtration, and disinfection, if used efficiently, usuallyprovide acceptable virus removal.
Parasites There are also many species of parasites carried bywastewater. The life cycle of each is peculiar to thegiven parasite. Some are dangerous to man andlivestock, particularly during certain stages of thelife cycle. Amoebic dysentery is a common diseasecaused by amoebic parasites. Chlorination,chemical precipitation, sedimentation, or sandfiltration is used to ensure protection againstparasites.
The world of microorganisms is made of:
MAJOR MICROBIAL GROUPS
Molds
Made up of a network ofbranched threadlikestructures called hyphaewhich grows to form atangled mass calledmycellium.
Yeasts
They occur constantly as single budding cells and do not form the branching filaments which characterized the molds.
Bacteria
