《环境工程专业英语》PPT课件.ppt

Environment 环境工程专业英语 主讲讲人：杨卫华杨卫华 河北工程学院城建系环环境教研室 Environment 成绩评绩评 定 Quiz （10） Performance in class（10） Seminar （20） Test （50） check on work attendance （10 ） Environment 课时课时 安排 Environment Environment Environment Environment Engineering Interactions with the Environment February 2004 The Microbiology of Activated Sludge Environment Water Treatment Wastewater Treatment Run-off Surface water Potable WaterRaw SewageAbstractionInfiltration Rainwater Groundwater Material Inputs e.g food if the F/M ratio is low, the bug normally grow very slowly (because little food is available for growth). F:M (Food to Microorganism ratio) Environment Microorganisms need oxygen to live. Oxygen use and be used to determine the activity of the organisms. - Actively growing organisms are rapidly metabolizing the food, so they are use oxygen at a rapid rate. - We measure the rate at which oxygen is used by a test called the Oxygen Uptake Rate (OUR), or the Respiration Rate. It is measured in mg O2/hr/gm of MLSS. - Normally a higher uptake rate is associated with high F/M ratios and younger sludges and a lower uptake rate is associated with lower F/M and older sludges. So, if you want a higher uptake rate, more sludge should be wasted. Less should be wasted if you want a lower F/M ratio. The Use of Oxygen Environment The Formation of Floc As bacteria begin growing, they generally develop into small chains or clumps. They are very active and motile and it is difficult for them to settle. They have not yet developed the slime layer which aids in their sticking together. So, when mixing occurs, the small chains or clumps are broken up and the bugs are dispersed, and they will not flocculate or settle. As the sludge is allowed to age, the bugs lose their motility and accumulate more slime. Then the clumps and chains are better able to stick together. The clumps grow bigger and bigger until they form a floc. If the organisms are allowed to develop properly, under the right conditions, the floc get large and compact and begin to settle. The mixing in the aeration tank tends to keep the floc small since, even though the bugs are sticky, the bond formed holding the organisms together is not very strong. This is good because it allows the cells, food, and oxygen to contact each other. Environment Dissolved Oxygen Oxygen is required by these bugs to metabolize food for cell maintenance and growth. Although the bugs need oxygen, some bugs can get along with less oxygen than others. Each bug must have a dissolved oxygen of at least from 0.1-0.3 mg/L to function properly. So, it is important to maintain about 2 mg/L of D.O. in the activated sludge so that the bacteria that are contained in the floc can get oxygen. If the DO is less than 2 mg/L, the bugs on the outside of the floc use the DO before it can get to the center of the floc. If this happens, the bugs in the center may die causing the floc to break up. Environment The Effects of Mixing Mixing is required to bring organisms, oxygen, and nutrients together, and to remove metabolic waste products. If there is not enough mixing, proper treatment will not take place because of lack of contact between the bugs, their food and oxygen. If too much mixing is provided, it can cause break up of floc or formation of unstable floc particles. Environment The Effects of pH The enzymes which regulate many of the biochemical reaction in bacteria are very pH dependent. The optimum pH should be between 7.0 and 7.5 for the proper activated sludge microorganisms to dominate. Environment The Effects of Temperature Biochemical reactions are very temperature dependent. Lower temperatures cause such reactions to be much slower. Thus, more bugs are required to do the same job during the winter than in the summer. . Environment The Effects of Nutrients Microorganisms require certain nutrients for growth. The basic nutrients of abundance in normal raw sewage are carbon (C), nitrogen (N), phosphorus (P), with the ratio of C:N:P ratio approximately equal to 100:10:1. In addition to C,N,and P, trace amounts of sodium (Na), Potassium (K), magnesium (Mg), iron (Fe), and many others are required. In normal municipal sewage, most of these nutrients are provided. Most problems with nutrient deficiency occur when there is a lot of industrial wastes present. When proper nutrients are not available, the metabolism fails and a kind of bacterial fat (slime) will begin to accumulates around the cell. The cell slows down in activity because it cannot produce enough enzymes and because needed nutrients cannot penetrate the slime layer as they should. The sludge will not settle and BOD removal slows down. Environment Engineering Interactions with the Environment February 2004 Protozoa low assimable organic compounds used to prevent biological regrowth) Pellets to road fill Sludge filtered Sludge to land disposal (v. small amount) Environment Regulation and Effect on Treatment USA - Disinfectants and disinfectant by- products rule enhanced coagulation more sludge, MIEX regenerant USA - Arsenic concentration from 50 ppb to 10 ppb Enhanced coagulation, reduction, ion exchange UK - Cryptosporidium concentration 10 oocysts/10 L Filtration of all water supplies Environment Sludge Disposal Inorganic sludges High in Fe and Al (little nutrient value, used as fill in construction, fire breaks) Organic Sludges organic cf cities 0.1/house not sustainable N & P uptake Environment Wastewater Collection Exfiltration To STP Environment Biological Wastewater Treatment Sewage Effluent NO3 Screens Primary Sedimentation Anaerobic Aerobic Anaer. Digester Sludge Sludge CO2, N2 O2 CO2 CH4 NH4, PO4 PO4 Prec Ca, Fe Precip. Cell synthesis requires: 100 C : 10 N : 1-5 P require extra C to remove P Environment Chemical Wastewater Treatment Coagulation (Al, Fe, Poly.) Solid/liquid separation (Filt. Sed.) High Rate Biological Inorganic sludge (Solids and PO4) Organic sludge (Soluble BOD, Small P & N) Sewage Effluent NH4, NO3 Good for short sewers Small footprint N removal a problem Total energy consumption may be less than biological treatment. Environment Discharge to water course Ocean discharge (N limited) 8 mg/L N, 3 mg/l P Freshwater discharge - P limited typical limits of 5 mg/L N, 0.5 mg/L P Typical treatment plant qualities Primary treatment 70mg/L BOD, 40mg/L N, 6mg/L P Secondary 20mg/L BOD, 20mg/L N, 3mg/L P Tertiary 10mg/L BOD, 5mg/L N, 0.5mg/L P Environment Wastewater Treatment Screens Primary Sedimentation Aerobic Sludge O2 CO2 Effluent to re-use Water reuse (Victoria 20% by 2020) 20 mg/L BOD, 30 mg/L TSS, Class A 1 cfu/100 ml no restrictions, (spray irrigation) Class B 10 cfu/100ml limited restrictions, (drip irrigation) Class C 1000 cfu/100 ml restricted access Nutrients and salt determine area of land required. Environment Stormwater Purpose Reduce flooding Separate stormwater system or combined sewer -stormwater system Problems picks up contaminants : heavy metals, PAHs, nutrients, pathogens, algal blooms, contaminated sediments flash flows Environment Traditional Approach to Water Services Water Supply - Large scale water supply from a few large sources Stormwater - Collect it all and discharge to receiving waters, engineer water courses and drains Sewage - Collect it all and discharge it after treatment to receiving waters Big Pipes In - Big Pipes Out Newman and Mouritz 1994 Environment Problems with traditional approach Receiving waters degraded by organic and nutrient loads Water supply augmentation solutions are becoming economically and environmentally questionable. Urban creeks and wetlands are being valued for their ecology and not just their ability to channel water away. Cost of big pipe infrastructure is becoming too highMouritz 2000 Environment Alternative water sources Use of stormwater for non-potable uses eg. toilet flushing, garden watering, industrial wetland, rainwater tanks, aquifer storage and recovery (ASR) reduces potable water required, decreases runoff, decreases contaminants to receiving waters Use of wastewater for non-potable uses eg. toilet flushing, garden watering, industrial wetlands, ASR, sewer mining, agricultural reuse applications reduces potable water required, decreases contaminants to receiving waters Combinations of above Non-structural approaches eg. low water use appliances Environment Rainwater collection Source of soft water Wide range of possible end uses Minimal pumping energy DIY at low cost Reduces storm water flows Environment Rainwater collection Environment Rainwater collection Green roofs - reduced renovation, energy and sewer costs (Case study Erisco Bauder and Integer house) Porous paving - reduced storm water flows Environment Rainwater collection Tank sizing calculation Too large: no overflow and cost implication Too small:continual overflow and minimal savings Roof area, local rainfall, building occupancy and usage Tank location In temperate climates - Underground or in a building to minimise frost and sunlight exposure Interruption of supply is likely during very dry periods Environment Greywater use Variations due to: Building type Climate Appliances used Occupancy level, age, gender, lifestyle Storage is generally required for a single house 80% savings in toilet flushing requires 50 l storage* (UK) *Dixon et al. Water Science and Technology Volume 39, Issue 5, 1999, Pages 25-32 Environment Greywater use Various sources BOD5 (mg/l) Turb (NTU) NH3 (mg/l) P (mg/l) Total coliforms Hand basin1099.62.58 Combined1216910.36 Single person 11014 Single family 76.50.749.3 Block of flats 3320100.41x106 College 805910 Large college 96570.82.45.2x106 (cfu/100ml) Environment Public perception WROCS report, 2000 Environment Alternative wastewater services Separate blackwater and greywater treatment dual wastewater pipes, reticulated greywater collection and on-site blackwater storage/collection, scheduled flows, on-site greywater reuse better processes to handle and recover nutrients Treated greywater available for reuse Localised treatment high potential for reuse, higher accountability for wastes generated Environment Techniques and technologies Separating toilets Waterless urinals Vacuum toilets Separation devices Composting chambers Environment Techniques and technologies Separating toilets Waterless urinals Vacuum toilets Separation devices Composting chambers Aquatron biological toilet system Environment Techniques and technologies Separating toilets Waterless urinals Vacuum toilets Separation devices Composting chambers Heat Compost Environment Toarp Eco-village, Sweden Constructed 1992 37 houses Water supply and sanitation selected by Swedish Building Cooperative Case Study Greywater Sedimentation Sand filter Irrigation Overflow to local brook Heat Compost Environment Case study Operational problems and issues Smell, flies and humidity Compost chamber access High energy demand for heating element Very wet compost Solutions Basic instruction and information transfer Operation and maintenance schedule Expert advice available Installation of separating toilets Environment Lubeck Sustainable Development Garden Overflow Land infiltration ( toilet flushing) Sludge to farms Heat recovery Blackwater (Vacuum sewer) Greywater Wetlands Anaerobic digestion Grass/Carpark Environment Alternative Stormwater Drainage Water Sensitive Urban Design Reducing paved areas, grass swales, appropriate trees for water/nutrient uptake, wetlands for storage & slow seepage to ground, roads follow contours, rates based on impervious area Sustained flows, reduced contaminants to receiving waters Stormwater reuse rain water tanks, wetlands reduces potable water required, decreases runoff, decreases contaminants to receiving waters Environment Water Sensitive Urban Design Reduces runoff by diverting water to ground infiltration Reducing paved areas grass swales appropriate trees for water/nutrient uptake wetlands for storage & slow seepage to ground roads follow contours Environment Environ