STPs are put in place to treat wastewater arising from a building while assuming certain inflow volume, flow pattern, and pollution characteristics. When in operation, the plant is expected to perform its treatment by purifying the entire inflow flawlessly. In case any of the design criteria are out of the design consideration it becomes difficult to rectify or treat the wastewater generated.
Wrong design
We often encounter sewage treatment plants that are poorly designed. This can happen due to several reasons such as under-designing of the treatment plant capacity, a small collection/equalization tank resulting in overflowing collection, inadequate aeration in the reactor, unnecessary aeration in the collection tank and treated water tank, pumps with higher flow than design flow, improper sludge recycling and wasting methods, and very large pressure sand and carbon filters that use almost half of the daily flow for backwash.
Operational issues
A sewage treatment plant that relies solely on the operator's skills is a poorly designed STP. Operators often make decisions about aeration and flow into the reactor without any scientific understanding of how it affects microbial activity and purification. Some plants rely heavily on filtration and disinfection to remove odor and color, resulting in the frequent replacement of filter media. This can lead to further operational problems if the plant is not properly designed.
User issues
Many individuals are not aware of what can be sent for treatment and mistakenly believe that everything that goes down the drain can be treated. However, there are harmful substances such as paints and thinners that are sometimes dumped, which can severely compromise the sewage treatment plant. Furthermore, some buildings operate industrial kitchens and dispose of large amounts of food waste down the sinks. This practice increases the organic load, which can further compromise the treatment process.
Wrong choice of treatment option
Choosing anaerobic treatment systems with very low hydraulic retention time is sometimes preferred as a cheap and cost-effective treatment option.
