Post on 23-Feb-2016
description
Water Quality Considerations for
TreatmentWater sources
PollutionTreatment needs
Hydrological cycle
Water retention in aquifers
Volume of water in the atmosphere (if condensed) ~ 3,100 mi3 or 12,900 km3 = 0.001 % of Earth's total water volume= 0.035% of all fresh water = 4.5% of all surface water= 1 inch to cover all of Earth’s surface
Atmosphere: superhighway for fresh water cycle around the globe
Atmospheric water
Rainfall distribution on Earth
World climatic areas
World climatic areas
Safe and reliable supplies of water
Not without environmental consequences
Ensuring supplies
Alternative water sources
Promising, yet elusive
Hypoxia
Hypoxia Mississippi Delta
Fertilizer and nitrogen cycle
Effect of Salinity on SoilsSalinity: Sodium and ChlorideGood Salts: Calcium, Magnesium Hold soil particles togetherProblem Salts: Sodium – soil dispersion Chloride - toxicity
Ca++
Mg++
Na+
Sodium Absorption Ratio (SAR)
Consequences of Soil DispersionPoor DrainageLess infiltration of waterIncreased water runoffLess efficient leaching of salt
Loss of Soil StructureLoss of soil pore spaceDecreased oxygenIncreased soil erosion
Plant EffectsHigh soil bulk densityDecreased root growthAnoxia and root death
Poor water infiltration leads to soil ponding: poor leaching,salt accumulation, low soil oxygen, root death fromanoxia, and increased Phytophthora root rot.
The effect of salinity on plants
Chloride 0.61%
Chloride 0.58% Sodium 0.35%
Environmental protection
Typical water treatment process with lime softening
Water reclamation
Process units in water treatmentPre-chlorination – for algae control and arresting any biological growthAeration – along with pre-chlorination for removal of dissolved iron and manganese and stripping volatilesCoagulation – for flocculationCoagulant aids, such as polyelectrolytes – to improve coagulation and for denser floc formationSedimentation – for initial solids separation, that is, removal of suspended solids trapped in the flocFiltration – removing additional solids from waterDesalination – removing soluble inorganics from waterSoftening – removing calcium from waterDisinfection – inactivating microbesAdsorption – removing undesirable organic compounds
Reflection The general technologies are well developed and generalized designs are available which are used by many water utilities (public or private)
No unique solution (selection of unit processes) for any type of water New technologies are still developedDifficult to standardize unit processes for different water sources. Treatability studies for each source of water in different seasons required for appropriate processes.