In a conventional waste water treatment system, black water and grey water go through a single pipe. While there is no imminent harm in that, it’s been proven that separating the two provides a lot of benefits. Some researchers are trying to find ways to implement this system in commercial water treatment systems.
Grey Versus Black
Black water is a type of waste water that comes into contact with solid human waste. On the other hand, grey water is a relatively cleaner waste water that comes from bathtubs, showers, washing machines, and sinks. Unlike grey water, black water may contain pathogens present in faecal matter.
Defining Source Separation
When black water and grey water are mixed, the resulting effluent must be treated as black water. This means that the receiving sewage treatment plant will have to adopt a complex purification system. Source separation is the method of collecting black water and grey water in separate tanks, where the two will undergo different treatment processes. This is a technique adopted by some commercial water treatment systems because of the advantages it offers.
Separating waste water sources helps improve the capacity of treatment plants by maximising the reuse potential of both grey water and black water. In a ten-month test study of source separation conducted by AP System Engineering in Germany, it was found that grey water can be reused in showers and washing machines, while black water can be reused for flushing toilets. This shows that source separation increases the efficiency of waste water treatment. Another advantage of source separation is that it lessens the risk of contamination. In sewers, leakage is much more detrimental because mixed waste water may contain pathogenic bacteria. When the leaks seep through groundwater supply, it poses a risk to public health. Separate treatment of waste water ensures that black water is contained properly and does not intermix with other waste water, let alone leak. Source separation is still not widely practised. Nonetheless, it’s a promising technique that we already see in eco-waste water systems that implement tailored processes for each kind of waste water.