BOD / TSS / pH Compliance
Control The Algae, Control Your BOD, TSS, & pH
As mandated by the U.S. EPA, the BOD and TSS discharge limits for lagoons are usually 30 mg/l and 45 mg/l respectively. Over 90% of all lagoon BOD / TSS violations are caused by too much algae in the final cell. To keep algae in balance is to keep your system in balance. But beware false BOD readings! Learn more here.
TSS are most commonly comprised of biomass (bacteria, a CBOD material, usually 7 mg/l), algae (also a CBOD material, often 50% of the TSS) , and miscellaneous clay or sludge particles. As an example, a TSS level of 50 mg/l would likely have a CBOD level of (7 + (0.5 x 50)) = 32 mg/l CBOD5. High TSS can be caused by short-circuiting, short detention times due to sludge buildup, pond turnover, and/or pass-through of excessive sludge buildup. Proper mixing and circulation reduces short-circuiting & sludge pass-through while encouraging flocculation. The resulting decrease in stratification will result in fewer and less severe turnovers that lead to high TSS levels.
High pH above the mostly standard 9.0 discharge limit is usually caused by excessive algae or low alkalinity (where even a small algae crop can create a significant rise in pH). Maintaining good circulation in all ponds will cause nutrient reductions (carbon, nitrogen, and phosphorus) across the board and will also stabilize the sludge thus minimizing any associated nutrient feedback. Less nutrients in the final cell equals less algae in the final cell which helps keep pH at acceptable levels of 8.0 to 9.0.
There are some other tips to consider when working to keep your pH below violation. Algae driven photosynthesis occurs most prolifically near the water surface and drives pH upward. Check that the effluent pipe is not discharging from the "highest pH" surface of the pond. If the alkalinity is too low (as mentioned above, i.e. 40 mg/l), consider adding lime to the water to help level out wild pH fluctuations low alkalinity can cause.
Low pH on the other hand can be caused by excessive volatile sludge stuck in the acid phase, excessive loading, excessive daphnia, or extreme nitrification. Check whether the aerators are mixing up the anaerobic sludge or if the influent pipe is depositing low pH water onto the surface. Low pH often means an unhealthy system out of balance which inhibits good algae growth. While algae can be the cause of excessive pH, lack of algae can cause the pendulum to swing the other way as well. Again, good circulation and mixing is key as it provides an algae balance which can keep both high and low pH conditions at bay.
Please explore "Related Equipment" to find out which machines can help!