Plutocalc Designer may not be optimal, but I think it is free and is Excal based.

Thank you, Jim. The tools that they have are for Activated sludge and MBR. I am still looking for any other option.

In areas where there is a limited amount of space, treatment takes place in a single basin instead of multiple basins, allowing for a smaller footprint. Low total-suspended-solid values of less than 10 milligrams per liter (mg/L) can be achieved consistently through the use of effective decanters that eliminate the need for a separate clarifier. The treatment cycle can be adjusted to undergo aerobic, anaerobic, and anoxic conditions in order to achieve biological nutrient removal, including nitrification, denitrification, and some phosphorus removal. Biochemical oxygen demand (BOD) levels of less than 5 mg/L can be achieved consistently. Total nitrogen limits of less than 5 mg/L can also be achieved by aerobic conversion of ammonia to nitrates (nitrification) and anoxic conversion of nitrates to nitrogen gas (denitrification) within the same tank. Low phosphorus limits of less than 2 mg/L can be attained by using a combination of biological treatment (anaerobic phosphorus absorbing organisms) and chemical agents (aluminum or iron salts) within the vessel and treatment cycle..All SBR designs should have a minimum of two basins to allow for redundancy, maintenance, high flows, and seasonal variations. Two basins allow for redundancy throughout the plant. If one basin is off line, the plant is still able to treat influent wastewater because of the equalization basin.

https://youtu.be/h4z979NFmWA

https://www.researchgate.net/publication/341870756_Trouble_Shooting_in_Water_Treatment_Process_for_Variable_TDS?_sg=mKUgRPLARLPmwz0OaPlbuT-7HiPqwAh96CnqZ5D-ZzhOIjPazwu2VInQidK_0zA7g1wNmReFAR0Sx0XfEMuY3axyfbQEakT9P3_neWig.3TqEuORBw756VjJND5c6pKrIjSD1WkYZiky-QNVpYe7kXEgoGF4Kw4aOpvD_K8INPBiU5Kg639SbZmWFKmor7g