so, because this is steel
recycling rather than
smelting, almost exactly none of the energy used in the process ends up in the final product; 99% or more of it is lost as heat during the manufacturing process. one of the things mentioned in the video is that this furnace uses more electrical power than the entire neighboring town of witten (population 0.1 million), which means that you could heat
all the houses. but you'd still need the big basins, because all the houses might not be enough to cool the furnace; certainly in the summer they wouldn't want to
creating electricity is unfortunately somewhat less practical due to the low temperatures of the water, although there are some interesting experiments with deriving power from low-temperature geothermal resources using n-pentane-blown turbines, and you might be able to use that work. getting the furnace's water jacket hot enough to boil water would create the risk of a steam explosion as well as increase plumbing corrosion problems
i mean, it would create a larger risk than the one that already exists due to having a water jacket in a place where a furnace damage could mix water with molten steel—as it turns out, cooling water is already the major cause of fatal accidents in electric arc furnaces, causing several fatal electric arc furnace explosion accidents every year: https://www.aist.org/AIST/aist/AIST/Publications/safety%20fi... and this is stimulating a movement away from pressurized water jackets for electric arc furnaces (at least, if we can believe this marketing white paper from a company that sells non-pressurized electric arc furnace water-cooling systems)
you could conceivably use a different, higher-temperature coolant than water, such as molten salts or sodium, as is done in nuclear reactors, so you could have an unpressurized coolant loop (maybe even using a coolant that wouldn't react violently with molten steel the way water does) but these do have disadvantages; water has a really astonishing ability to transfer heat by nucleate boiling
but then you run into the cost issue: the reason coal plants are not able to produce electricity at a price that is competitive with solar farms is, as i understand it, that the steam-turbine and electromechanical generator part of the plant still cost more than solar power, even in very polar countries like germany, whose utility-scale photovoltaic capacity factor was 10% last i checked. it's not because of the cost of coal; even if coal was as free sunlight, they'd be uncompetitive. and the same cost problem would make it uneconomic to generate electricity from the waste heat from electric arc furnaces, even if you could get the heat out at a more useful temperature. every million dollars you hypothetically spend on recycling eaf waste heat into electricity would have produced more electricity if you had spent it on solar farms and wind turbines instead
district heating is a good idea tho. i wonder if witten is already doing it?