“How can governments create loans to pay for infrastructure projects?”
One of the most discussed subjects in local politics is infrastructure investment. Whether it’s planning new metro stops for commuters, creating green infrastructure for flood resilience in a marginalized community, or building a new wastewater treatment plant for a rapidly growing community, infrastructure is a core part of the public conversation. However, building these projects requires large capital investments that municipal governments may not have on hand. So what can they do? Well, governments have the power to issue Municipal Bonds for Infrastructure, or loan requests to finance specific projects. Investors can purchase these bonds by lending the required principal to governments, who can then use to fund their projects. Governments can repay these loans through raising tax revenues (known as a General Obligation (GO) Bond) or through revenue generated by the infrastructure investment (Revenue Bond). Loan providers like municipal bonds because interest on municipal bonds is generally exempt from federal taxes (and possibly state and local taxes if the loan provider is based in the same state/municipality, respectively). Interest rates on municipal bonds are typically lower because of these tax benefits. Municipal bonds for infrastructure are a cornerstone of modern infrastructure development, given the exponentially increasing need for new public works.
“How can we measure how much wastewater passes over a weir per length?”
Clarifiers slow wastewater flow speeds to ensure suspended solids float to the bottom and clean effluent rises to the top. Weirs are built into the perimeter of clarifier outlets to ensure the exit flow stays smooth and even. The amount of flow exiting per weir length, known as the Weir Overflow Rate, determines if the system is functioning normally or if flow is too quick and potentially carrying solids. Weir overflow rate is an important variable that all environmental engineers must consider when designing and monitoring clarifiers.
It’s common for people to associate “modern” wastewater treatment with towering industrial plants that look like they’re straight out of a Martian civilization. But what if I told you that ponds could also serve as effective wastewater treatment? Essentially, ponds can have bacteria that consume the organic matter in wastewater, producing cleaner effluent and carbon dioxide. Algae in the pond can absorb the CO2 and transform it into oxygen to feed the organic-matter-eating bacteria. These systems, known as Stabilization Ponds, are incredible for low-energy, high-land availability communities often found in numerous developing countries.
Sludge is a mixture of solid waste and water created after an industrial or water treatment process. The more water a body of sludge has, the more volume and weight it will take up, and the more difficult it is to handle. Draining water from the sludge will make it lighter and easier to operate. Sludge Dewatering is an essential tool for sludge operators.
“Why do we need to protect the perimeter of our construction site from releasing sediment with stormwater runoff?”
Construction operators are obligated to apply best management practices to prevent stormwater runoff sweeping sediment from their sites from entering water bodies. One of the most important aspects is ensuring the perimeter of the site is controlled. Perimeter Runoff Control strategies keep sediment inside the site. Silt fences and sediment basins are examples of perimeter runoff control. The National Pollutant Discharge Elimination System Construction Stormwater Permit requires construction operators to implement perimeter runoff control before beginning soil disturbing activity as part of their stormwater pollution prevention plans. Construction operators can temporarily dismantle perimeter control infrastructure to allow vehicles to enter the site, as long as the infrastructure is restored as soon as possible.
Reeds are wetland-based plants that can successfully populate large swaths of area, making Reedbeds. These reedbeds host special microorganisms in their root systems that clean wastewater by consuming sewage. Reedbeds are often utilized for constructed wetlands due to their wastewater cleansing capabilities.
“What makes those grass-like plants in wetlands special?”
If you look at pictures of wetlands, you’ll probably see tall grass-like plants. But what are they and what makes them special? Well, these plants are called Reeds. Reeds play a vital role in soil stabilization, waste treatment, nutrient management, and habitat creation. Reeds are a critical part of wetland functioning.
“How can we use air blowers to remove volatile organic compounds from water?”
Toxic volatile organic compounds (VOCs) might seep into water during the water cycle. According to Henry’s Law, low air pressure can remove these VOCs from water. So what if we were to push water into a tower with air from a giant air blower coming from the bottom and move it down while exposing as much surface area as possible to the low-pressure air to filter out the VOCs? This is the idea behind Air Stripping, a common method for treating VOCs in human-use water.
“How does mass move from one phase/substance to another?”
Substances in different phases or substances may come into contact with each other. This can cause the mass of a certain substance in one phase or concentration to move to another, such as through diffusion (one substance moving from a single concentration in another to uniform distribution), convection (mass transport by bulk motion of a surrounding fluid), absorption (chemical penetration of one substance into another), or distillation (separation of different components by different boiling points). This Mass Transfer is foundational to understanding how chemical engineering systems operate.
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