Pre-treatment is a critical part of the entire treatment plan when dealing with wastewater. How effectively it is implemented will dramatically affect primary treatment and impact how much maintenance is required for pre-treatment equipment.
Pre-treatment is most effectively done above ground. The primary reason for this is maintenance. Underground systems or equipment, while out of sight, are far more difficult to maintain and require confined space entry. Because there have been so many past incidents of workers becoming disabled in confined spaces, there are strict guidelines related to entry and operation in any confined space and it is always better to avoid creating them.
The first stage in pre-treatment is lifting wastewater above ground. The best way to accomplish this is with circular lift stations. Circular lift stations are self-cleaning, so they do not require pump-outs, as do in ground separators.
The second stage of pre-treatment is screening. Removing solids is an important step prior to any further treatment and is a big money saver. Many times the screened material can be handled either as compost or animal feed.
Once the wastewater is screened, solids settling is an option that can be effective if there is space and time. Many very fine and un-screenable solids will settle. An effective way to remove them is with cone bottom tanks. A cone bottom tank will concentrate sludge material into the bottom of the cone. It can then be removed to a storage tank, be sent to a dewatering hopper, or be sent to a filter press.
The final stage of pre-treatment is pH balancing. Further anaerobic or aerobic treatment requires a pH range that is close to neutral. Removing solids in the previous steps will dramatically reduce chemical consumption since solids act as sponges. The type of mixing in a pH system will also affect how much chemical is consumed.