WASTE WATER TREATMENT Flashcards
xsxsxs
Water Usage and Classification
Classification - Beneficial Use
1.) CLASS AA - Public Water Supply Class I
I. This class is intended primarily for waters having watersheds which are uninhabited and otherwise protected and which require only approved disinfection in order to meet the National Standards for Drinking Water (NSDW) of the Philippines Public Water Supply Class
2.) Class A - Public Water Supply Class II. For sources of water supply that will require complete treatment in order to meet the NSDW
3.) Class B- Recreational Water Class 1. For primary contact recreation such as bathing swimming, skin diving.
4.) Class C -Fishery Water for the propagation and growth of fish and other aquatic resources; Recreational Water Class II (Boating, etc.) *Industrial Water Supply Class I (For manufacturing processes after treatment).
5.) Class D - For agriculture, irrigation, livestock, watering, etc.
*Industrial Water Supply Class II (e.g. cooling, etc.)
Other inland waters, by their quality, belong to this classification
COAST and MARINE WATER
6.) Class SA - Waters suitable for the propagation, survival and harvesting of shellfish for commercial purposes, Tourist zones and national marine parks and reserves established under Presidential Proclamation No. 1801
7.) Class SB - Recreational Water Class I
Fishery Water Class I
8.) Class SC - Recreational Water Class II
Fishery Water Class II
Marshy and/or mangrove areas declared as fish and wildlife sanctuaries
9.) Class SD- Industrial Water Supply Class II
HARACTERISTICS OF WASTEWATER
(Physical, Chemical Characteristics, Biological)
physical charac of waste water
a. Physical Characteristics (COTTT)
1. Color- generally an indication of the age of sewage ( e.g.fresh: grayish or septic: black)
Measurement: Visual Comparison Method
Nessler Tubes – color comparison tubes containing water of different colors and assigned a color unit ranging from 1 to 70 where 1 color unit Pt = 1/2mg/L Co
Photoelectric Colorimeters
2. Odor – comes from the septic decomposition at organic wastes and is due to the presence of gases such as
Measurement:
Olfactometer
Sensory Method – panels of human subjects are initially exposed to odor free air and then sampled air which has been diluted with odor free air to give MDTOC. The number of dilutions give TON: MDTOC/TON
a. Physical Characteristics
where: MDTOC = minimum detectable threshold odor concentation
TON = threshold odor number
TON = vol. of sample air + vol. of fresh air/ volume of sample air
- Turbidity – the amount of suspended matter in water/wastewater and is obtained by measuring its light scattering activity. It is also a measure of the ability of sunlight to pass through water and the ability of water to disperse different materials disposed into it. A typical clear lake has a turbidity of about 25 units while muddy water exceeds 100 units
Measurement:
* Jackson Turbidimeter – JTU ( Jackson Turbidity Unit ; 1 unit
* Secchi Disk Depth – disk in which a secchi disk may still be visible to the naked eye when submerged in water. - Temperature -lowers the solubility of oxygen in water and increases the rate at which oxygen-consuming microbes attack organic waste
- Total Solids – solid residue when water is evaporated at 103 -105 ⁰ C
b. Chemical Characteristics
. pH – a measure of the acidity or alakalinity of water
2. Calcium and Magnesium Salts - cause hardness of water and the formation of scales and deposits on pipelines and fittings if used in industry
3. Nitrogen and Phosphorous – basic components of fertilizer, serves as nutrient for microbial growth in particular algae. Excessive amounts lead to algae blooms which caused eutrophication or the overabundance in the growth of algae giving water a pea soup appearance
4. Trace metals
5. Proteins – principal constituents of animal organisms and in large quantities causes extremely foul odor
6. Carbohydrates – include sugar, starches, cellulose and woof fiber sugar + bacteria ferment alcohol + CO₂
7. Oils, Fats, Greases – prevent natural aeration reducing the use of the stream for fishing
8. Surfactants – substances that cause foamimg in water
9. Phenols – cause taste problems in water particularly when the water is chlorinated
10.Pesticides and Agricultural Chemicals – have the capacity to biomagnify at certain concentrations; are carcinogenic
Biomagnification – involves the accumulation of trace metals through each species of the food chain
o Mercury – easily converted into the toxic methyl mercury which cause Minamata disease which is a neurological disease characterized by trembling, inability to walk and even serious convulsions that can lead to death
b. Chemical Characteristics
o Cadmium – responsible for the Itai-itai (ouch ouch) disease which is an extremely painful disease that caused disintegration of the bones
o Silver – causes argyria, the blue-gray discoloration of the skin and mucous membrane
o Arsenic – recognized poison; carcinogenic
o Chromium – causes neurological disease
- Measures of Organic Content o Dissolved Oxygen (DO)
o Theoretical Oxygen Demand (ThOD) – a measure of the amount of O₂ needed to oxidize completely an organic matter whose chemical formula is known
o Biological Oxygen Demand ( BOD ) – a measure of the amount of O₂ needed by microorganisms to decompose biodegradable organics at a specified time (5days ), temperature (20⁰C) and pH 7
o Chemical Oxygen Demand ( COD ) – a measure of the amount of O₂ needed to ixdize organics using strong oxidizing agents (KMnO₄ or K₂Cr₂O₇) in acid media
o Total Oxygen Demand ( TOD ) – organics are converted into stable and products in a Pt-catalyzed combustion chamber and is determined by monitoring the O₂ content present in the products
o Total Organic Carbon ( TOC ) – organic matter is oxidized in a high temperature furnace to convert C to CO₂
c. BIOLOGICAL Characteristics
- Measures of Organic Content o Dissolved Oxygen (DO)
- Kinetics of BOD
Components of Domestic Wastewater
Organic materials
Nitrogen
Phosphorous
Suspended solids
Pathogenic organisms
Wastewater Treatment Plant
- Preliminary Treatment –removal of large solids to prevent damage to the remainder of the unit operation
- Primary Treatment - removal of suspended solids by settling
- Secondary Treatment – removal of the demand for oxygen
- Tertiary ( or advanced)treatment – a name applied to any number or polishing or clean up processes, one of which is the removal of nutrients such as Phosphorous
- Solids Treatment and Disposal – the collection, stabiliza tion, and subsequent dissposal of the solids removed by other processes
PRIMARY TREATMENT
Physical Treatment Method
- Screening – treatment used for the removal of coarse or settleable interception
Types of Screen
Racks or Bar Screen – composed of parallel bars or rods which may be hand cleaned or mechanically cleansed
Fine screens – wire or cloth mesh or perforated plate
Purpose of Screening: To remove material which would (a) damage equipment (b) interfere with the satisfactory operation of a process , and (c) cause objectionable shore line conditions - Comminutors – device that cut up solids from the screens into pieces about 0.3 cm or smaller 3. Grit Chamber – an enlarged channel where the velocity of wastewater flow is controlled to allow only the heavier solids to settle
- Settling Tank (Sedimentation/Clarifier) – consists of cylindrical or rectangular tanks where settleable solids (raw sludge ) are removed by gravity
SECONDARY Treatment Chemical Treatment Methods
- Neutralization – a chemical treatment whereby acids or bases are added to the influent wastewater in order to neutralize any acids or bases present and thus control pH.
- Chemical Precipitation – involves the addition of chemicals for the express purpose of improving plant performance and removing specific components contained in wastewater.
- Coagulation – an electrochemical process used in the removal of colloidal matter in wastewater through the addition of coagulating agents which reduce the electrostatic charges surrounding colloidal matter, thereby allowing natural Van der Waals forces of attraction to predominate and allowing solids to cluster. Common Coagulants
o Alum- Al₂(SO₄)₃.7H₂O
o Copperas - FeSO₄.7H₂O - Chemical Flocculation – a physico-chemical process used in the removal of finely divided solids, a polyectrolyte is added to wastewater which can form bridges that will join together the solids.
- Disinfection – refer to the destruction of water forms pathogens ( bacteria, viruses, amoebic cysts) for the sole purpose of preventing of transmission of disease through water
- Ozonation – ozone (O₃) comes from the Greek word “ozein” which means to smell . It is a very unstable gas and a very powerful oxidant capable of oxidizing 200 – 300 times more than chlorine. It can reduce complex taste, odor and color. It has no lasting effect and is quite expensive and found to be toxic to fishes.
- Chlorination – addition of Cl₂ and its compounds ( Cl⁻ and HClO⁻)
o Chlorine when added to wastewater is broken down into: chlorine demand of water – amount of Cl₂ that will oxidize organic matter
o residual chlorine – amount of Cl₂ that will disinfect water
Chemical Treatment Methods Common Precipitants
Common Precipitants
Lime – Ca(OH)₂
Ferric Chloride - FeCl₃
Soda Ash - Na₂CO₃
Ferric Sulfate - Fe₂(SO₄)₃
Alum - Al₂(SO₄).7H₂O
Biological Treatment Methods
. Activated Sludge Process – a continuous recrculating aerobic biochemical process that keeps cells in suspended growth
2. Trickling Filters – a fixed bed where wastewater is intermittently discharged and contacted with biological slimes that have grown in the filter media.
3. Stabilization Pond – a large shallow lagoon divided by thermal stratification into an aerobic surface and anaerobic bottom
4. Aerated Lagoon – stabilization pond provided with surface aerators
5. Anaerobic Digestion or decomposition – generally employed for treatment of organic sludges and concentrated organic industrial waste
