1972: Federal Water Pollution Control Act PL 92-500 subsequently amended and now called the Clean Water Act established water quality goals fishable & swimmable and timetable established National Pollution Discharge Elimination System (NPDES) construction grants for WW treatment required secondary treatment (30/30)
Sludge Disinfection Sludge Preliminary Treatment To remove materials that will interfere with subsequent treatment
Coarse Screening (bar racks) Medium Screening Comminution Flow measuring Pumping Grit removal Pre-aeration Bar Racks
Metal bars spaced a few cm apart across water flow mechanical or manually cleaned size of unit set by approach velocity 0.6-1.0 m/s for mechanically cleaned 0.3-0.7 m/s for manually cleaned see Fig 10.4 and example 10.2 on pg. 311 Grit Removal
Grit chambers intended to remove sand, cinders, gravel that may enter system by cracks in pipes, inflow etc. Grit can cause excess wear in pipes and pumps small sedimentation tanks; designed with the help of Stokes Law no organics removal
Grit Chamber Primary Sedimentation Purpose: to remove suspended solids (smaller than grit, and less harmful) Typical efficiency 67% TSS removal 33% BOD removal
Design parameters overflow rate weir loading rate detention time Primary effluent is largely composed of soluble and colloidal organics which can be converted to settleable microbial solids and CO2 by biological treatment
Primary Sedimentation Primary Treatment Removes ~50% of suspended solids Parameter Design Range Typical Value Overflow Rate 35-45 m/d 800-1200 gal/ft2/d
40 m/d 1000 gal/ft2/d Detention Time 1.5-2.5 h 2h 2 2 125-500 m /d
275 m /d Weir loading 10,000-40,000 gal/ft/d 20,000 gal/ft/d rate Primary Sed. Tank Primary Clarifier: Center Feed Secondary Treatment
Generally includes some biological process plus secondary clarification Required under PL92-500 Converts soluble and colloidal organic materials to biomass and CO2 Biological Treatment Suspended Growth Activated Sludge Conventional, Extended Aeration, Contact Stabilization
Aerated lagoons Aerobic digestion Attached Growth Trickling Filters Rotating Biological Contactors Suspended Growth Systems Air Aeration Tank Return Activated Sludge
Secondary Sedimentation Sludge Waste Activated Sludge Attached Growth: Trickling Filters Rotary Distributor Rocks or Plastic Media Air Underdrain
With rocks, depth is limited to 2-3 m because of oxygen needs Rotating Biological Contactors Drum diameters are typically 10-12 ft. Rotation speed: ~1.5 rpm May be in several stages No flow recycle Requires piloting
Mechanical Dewatering Vacuum filtration, centrifugation, pressure filtr. Disposal land application, burial, incineration Anaerobic Digestion Sludge held without aeration for 10-90 days Process can be accelerated by heating to 35-40oC These are called High Rate Digestors (10-20 days) Advantages low solids production
useable methane gas produced Disadvantages high capital costs susceptibility to shocks and overloads Sludge Dewatering Sludge drying beds historically the most common sand bed, 15-30 days, evaporation & seepage Vacuum Filtration
cylindrical rotating drum covered with fabric submerged with applied vacuum Continuous belt filter presses (follows) Plate pressure filters vertical plates mounted on a frame Belt Filter Press (Komline-Sanderson)
Health and Living Conditions in Eight Indian Cities. ... To examine the intercity and intracity differentials in the health and living conditions of population by slum/non-slum residence and economic status in eight big cities of India. NFHS-3, India.
ANSWER: TRUE § 322.212, Fla. Stat. makes possession of a forged or stolen ID a third degree felony. This can include penalties up to arrest, a maximum of 5 years prison and/or probation, and a $5,000 fine.
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