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Article four (recovered) one plus Document Transcript

  • 1. Wastewater Treatment and Pollution Control SuperPro Designer can be used to model, evaluate, and optimize any type of Wastewater Treatment, Water Purification, and Air Pollutio Since SuperPro also handles a wide variety of chemical manufacturing processes, it is an ideal tool for evaluating Pollution Prevention an options and practicing Green Chemistry and Sustainable Development. EnviroPro Designer, a subset of SuperPro, mainly focuses on was treatment processes. EnviroPro/SuperPro Designer is a valuable tool for environmental consulting engineers, process and product designers, development eng scientists, treatment/disposal plant engineers and managers. It enables the user to efficiently develop, assess, and optimize environmen technologies. It provides under a single umbrella modeling of chemical manufacturing and end-of-pipe treatment processes, project eco evaluation, and environmental impact assessment. Modeling of Wastewater Treatment Processes EnviroPro Designer can be used to model, evaluate and optimize municipal as well as industrial wastewater treatment processes. It inclu operation models for biological as well as physical treatment. The flowsheet below shows a simplified activated sludge process that treat wastewater. EnviroPro also can be used to model and optimize nutrient (Nitrogen and Phosphorous) removal processes. For more info o removal, download the Evaluation version and have a look at the MUNWATER example (files b and c deal with nitrogen removal issues b Ludzack-Ettinger and Bardenpho processes).
  • 2. Unit Operation Models EnviroPro Designer features intuitive dialog windows for the initialization of unit operation models. In the following dialog window, the u the kinetic data of Benzene biodegradation in an aeration basin. Notice the expression for the overall reaction rate and the blocks for sp substrate, other, and biomass terms. The data for the reaction rate constants (Kmaxo, To, and Theta) as well as the half-saturation con substrate term (Ks) are retrieved from the component database but the user also has the option to overwrite them locally.
  • 3. EnviroPro Designer is equipped with rigorous biological reaction models. The models can handle any number and almost any type of rea biochemical oxidation, biomass decay, hydrolysis of particulate matter, chemical oxidation, photolysis, adsorption on particulate matter, can handle any number of biomass components (e.g., heterotrophic for biochemical oxidation and denitrification reactions, autotrophic f reactions, inactive biomass that decays, etc.). They support VOC emission calculations based on mass transfer and equilibrium-limited m accepted by EPA. Finally, they consider sorption of heavy metals and other compounds on sludge and track their fate. Physical and Environmental Component Properties EnviroPro Designer features extensive databanks of chemical components and mixtures. A User databank is provided for storing informa components created by the user. EnviroPro is also compatible with a version of DIPPR, a commercial physical property databank that inc reliable data for around 1,750 compounds.
  • 4. The pure component databank includes thermodynamic (e.g., molecular weight, critical pressure and temperature, accentric factor, vapo density, specific heat, particle size, etc.) as well as environmental (e.g., diffusivities in water and air, biodegradation data, octanol to wa distribution ratio, Henry’s law constant, component contribution to TOC, COD, BOD5, TSS, etc.) properties. The figure below shows som environmental properties for Benzene. The values of diffusivity (in water and air) are used for estimating emissions of this compounds fr (e.g., aeration basin) and quiescent (e.g., clarifier, thickener) tanks. The biodegradation parameters are used for estimating the extent o this compound in aeration basins (see second figure from top). The "Pollutant Categories" tab includes info used for regulatory reporting specifically, a compound can be classified as a volatile organic compound (VOC), Particulate, Acid Gas, ETG, CO, NOx, SO2, Base, etc. an used in Emissions Reporting.
  • 5. Versatile Material Balances EnviroPro Designer performs material balances on individual chemical components as opposed to environmental stream properties (e.g., etc.). This feature enables the user to track the fate (e.g., extent of biodegradation, volatilization, sorption on sludge, etc.) of regulated specific chemicals of interest in integrated water and wastewater treatment processes. Since wastewaters are typically complex mixtures compounds, the user may lump several components into one. For instance, Glucose on the dialog below represents all the soluble and e biodegradable organic compounds.
  • 6. EnviroPro Designer calculates a number of stream environmental properties (see figure below) based on the composition of streams and component contribution to these properties. This information along with some other pertinent data are used to characterize waste stream regulatory and environmental impact viewpoint.
  • 7. Additional Information 1. Go to the Literature page, scroll to the bottom and download the EnviroPro brochure and the paper on Water Treatment and R 2. Go to the EnviroPro page and scroll to the bottom to see a list of the papers written on EnviroPro. 3. Download the Evaluation and/or the Demo version of SuperPro and have a look at the five environmental examples that come software tool. Each example has a detailed ReadMe file. 4. Go to the Water Purification page for more info on water purification and recycling applications, production of ultrapure water, thorough example on water recycling at a semiconductor manufacturing plant. 5. Go to the Emissions page for info on emissions of volatile organic compounds (VOCs) from wastewater treatment plants and ch manufacturing facilities. Web sites
  • 8. Day 2 Day 3 Day 4 Treatment Process WHAT IS WASTEWATER? Wastewater is liquid waste. It is animal, vegetable, mineral or chemical matter in solution or in suspension that residents and businesses flush down their toilets and pour down their sinks and drains. Wastewater drains into a network of pipes maintained by sewer serviced municipalities and the Regional District of Nanaimo. Sewer systems are built to follow the natural slope of land, generally flowing towards the sea front. This design allows gravity to do most of the work transporting the wastewater to one of four wastewater treatment plants. For residential areas that are lower than adjacent lands or treatment plants, the wastewater must pass through a pumping station to pump the liquid into the plants. Treatment of our wastewater is an essential process that prevents contamination and destruction of our waterways, and our natural water resources. HOW IS WASTEWATER TREATED IN THE RDN? Generally wastewater treatment involves the following processes:
  • 9. Preliminary treatment - The velocity of the wastewater from the sewer lines is reduced as it enters the treatment plant. This allows sand, gravel and other heavy materials to settle out into grit tanks. Mechanical cleaning bar screens then remove rags, sticks, plastic and other foreign objects from the wastewater; this part of the treatment plant is called the headworks. Bar screens may be used before or after the grit tanks. All removed material collected by grit tanks and bar screens is washed and then taken to a sanitary landfill for disposal. Primary treatment - Primary treatment allows for the physical separation of solids and grease from the wastewater, and removes between 30-40 percent of Biological Oxygen Demand and 50 per cent of Total Suspended Solids. The screened wastewater flows into a primary settling tank where it is held for several hours allowing solid particles to settle to the bottom of the tank. Fats, oil and grease (FOG) are skimmed from the tanks, dried and sent to the landfill. The settled particles are known as primary sludge, which is collected and pumped to large digestion or holding tanks for further treatment and solids processing. Presently, Greater Nanaimo and Nanoose Wastewater Treatment Plants provide primary treatment and discharge treated effluent to the ocean. Secondary treatment - Secondary treatment is a biological treatment process that removes up to 90 percent of BOD and TSS. Following primary treatment, effluent is pumped to the secondary treatment stage. It may take one of several forms; for example, either a trickling filter or a sequencing batch reactor. The growth of microorgisms results from the consumption of organic matter in the wastewater as their food supply.
  • 10. The micro-organisms create a solid organic material (sludge), which just like the sludge from primary treatment. Secondary sludge is thickened and pumped to digesters for processing and solids processing. The French Creek and Duke Point Treatment Plants discharge secondary treated effluent into the Strait Georgia. Final treatment - The wastewater that remains can be disinfected to kill harmful micro-organisms before being released into receiving waters. Although there are many methods available to kill these micro- organisms, ultraviolet disinfection is the method used at Duke Point Pollution Control Centre. This is the only treatment plant in the RDN with this technology. At this stage, the treated wastewater, now called final effluent, is discharged into the marine environment. Solids processing - Primary solids from the primary settling tank and secondary solids from the clarifier are sent to digesters for solids processing. During this process, micro-organisms use the organic material present in the solids as a food source and convert it to by-products such as methane gas and water. Digestion results in a 90% reduction of pathogens and the production of a wet soil-like material called "biosolids" that contain 95-97% water. In order to remove some of this water, mechanical equipment such as a belt filter press or centrifuge are used to squeeze water from the biosolids, reducing its volume prior to being used in soil amendment or composting. MINI GLOSSARY BOD5 (Biochemical Oxygen Demand) is a measure of the quantity of oxygen consumed by microorganisms to break down organic matter in water. A high BOD means that there will be less oxygen; and oxygen is essential for the survival of aquatic life. Thus, high BOD levels result in the contamination of the receiving (marine) environment. TSS (Total Suspended Solids) are solid pollutants that would be captured on a fine filter paper. They are visible in water and decrease water clarity. High concentrations of TSS can cause many problems for aquatic life.