My name is Peter, and I'm going to give you an introduction to Integrated Urban Drainage and Wastewater Systems. Let me start by a worldview. This is Denmark, and my presentation will focus at the systems located in the capital of Denmark, called Copenhagen. Copenhagen is actually an old city, and when you look at it from the sky, you can see some of the structures that have been there for many years, including the old defense work in the inner city. The channel that goes through the system, and actually a small lake located out here. In nice weather, the receiving waters and the channel systems look like this. And to a very large extent, this is because of heavy investments in wastewater infrastructure. This is a picture of one of the big wastewater treatment plants located in the city. But let's have a look from a more technical perspective. You can recognize here the old water system that was part of the defense works of Copenhagen and the lake that I pointed out before. Actually, that's a river going through the system. In the off-stream part, there's a change from a natural appearance of the river into a channelized system, and down here is what we refer to as a combined sewer overflow. And down here is the wastewater treatment plant. This river actually has an important function in draining the city. The whole city is equipped with a wastewater system and a drain system that drains the water throughout the city, and this river plays a role in that context. This is how the lowest ratings which are generalized looks in dry weather. But when it starts raining, and the rainwater collects on the surfaces, runs into the drainage systems, which are then too small because of the heavy rainfall. The manhole starts to surge out, and this combines so offloads goes into function. This means basically that a mixture of rain water, storm water, and wastewater is discharged into the environment. This is a picture of the same part of the channel after heavy rainfall, and when you take a closer look, we can see that there are severe water quality problems. This is where the dirty wastewater mixes with the clean water. But let's take a more technical view on the whole integrated system that I'm talking about here. In reality, when we talk about an integrated urban water system that consists of groundwater, drinking water systems, drinking water distribution systems, rest of the city. There's a drainage system or a sewer system, in this case, a combined sewer system. There's a wastewater treatment plant and then a receiving water. When it rains, water, of course, infiltrates and replenishes the ground water reservoirs and also the base flow of the river systems. In Denmark, drinking water supply is to a very large extent based on ground water, but it could essentially also be based on surface water. What happens is that the water resources are extracted, brought to treatment systems, and distributed into the city where it is consumed. So the water used in industry or in households is discharged to the sewage system, and from there, it is conveyed to the wastewater treatment plant where the waste products are concentrated and disposed of as waste, and this water is actually so clean that it can be discharged directly into the environment. These systems are not perfect, so they are cross connections, the sewer system is not completely water proof, so there's ground water, exfiltration and infiltration. When it rains, the system receives more water, and more waters goes through the treatment plant, which typically has an affect on the water quality in the outlet from the treatment plant. When it rains a lot, these combined sewer systems, combine sewer overflow structures go into function, and this mixture of wastewater and storm water goes directly into the receiving water. This part of the system is what our course is about. A civil engineer would call it an integrated urban drainage system, because civil engineers tend to focus on the drainage infrastructure. A chemical engineer tend to call this an integrated urban wastewater system because chemical engineers tend to have that focus. You will find both terms in the literature essentially meaning the same. What is important when studying this system is that dynamics. It is also very important to maintain an integrated perspective on this, and that's not so easy because of the complexity to the system. And this is where models can be helpful, as you will see in this course.
