Wastewater Flashcards
What are the 2 goals of the Clean Water Act?
- To provide fishable/swimmable waters 2. Total elimination of pollutant discharge by 1983
Where are CWA permits applicable? CWA standards established conventional and non-conventional pollutants. Name examples from each. (5 + 4)
CWA permits apply to POTW
Conventional: BOD, TSS, pH, oil/grease, fecal coliform
Non-conventional: chemical oxygen demand, total organic carbon, total solids, NH3
How is an ambient water quality criterion established? (5 steps)
- lit review of toxic effects on aquatic life
- find effect on most sensitive species
- apply safety factor
- list safe concentration
- assume/list excursion frequency used to derive discharge standard
What is the difference between a technology-based and water quality-based standard?
Technology-Based: sets limit on concentration discharged; easy to enforce; set by EPA
Water Quality-Based: recognizes variability in quality & use of receiving water; more cost-effective; considers dilution of receiving water; set by states
What are 4 considerations in the development of a water quality-based wastewater discharge standard?
- characteristics of receiving water
- chemical content of waste, maximum discharge rate, minimum receiving water flow
- whole effluent toxicity testing
- sample monthly, report quarterly
What are 4 reasons for pre-treatment?
- Prevent dangerous conditions (eg, explosion)
- Prevent interference with city system
- Prevent pass-through of city system
- Prevent sludge contamination
Describe a typical municipal wastewater system.
What is primary wastewater treatment?
Removal of solids using screening, filters, grinding
What is secondary wastewater treatment?
Primary + Biological Treatment
Microorganisms break down contaminants
If only secondary treatment was used, bacteria would be released along with water.
What is tertiary wastewater treatment?
Tertiary treatment uses final sand filtration to further reduce BOD.
In nutrient removal, what two nutrients are removed?
What are some techniques for nutrient removal?
Phosphorous & Nitrogen
Techniques:
aerobic activated sludge processing
anaerobic treatment
enhanced biological removal
coagulation/precipitation
What are biosolids? Why are they beneficial? What are public health risks?
Biosolids: nutrient-rich organic materials from treatment of domestic sewage
Benefits: recycled for fertilizer and soil ammendment to stimulate plant growth
Risk: may contain low levels of pathogens or toxic chemicals
