Q. My plant is located in a water basin that reports to large lakes. My new permit limits pH, BOD, TKN, TSS, many metals, and phophates. What are they? How do I control these?
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A. Water that reports to a POTW (Publicly Owned Treatment Works) first, is regulated by the local authority according to its abilities and its restrictions under its NPDES (National Pollution Discharge Elimination System) permit. Since most of their treatment is finalized with live lagoons, they must limit your concentrations to what the lagoons can effectively handle.
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Extremes in pH (usually beyond the 5 to 9 range) slow the microbial action in the lagoon, and in severe cases, require neutralization, an extra and costly step.
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BOD stands for Biological Oxygen Demand. It represents how much work that the microbes need to do before the water can leave the lagoon. Very high BOD numbers increase the amount and, more importantly, time of microbial action required. The POTW may not have enough residence in its lagoons to handle severe cases.
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TKN is a measure of Nitrogen species in the water. It stands for Total Kjeldahl Nitrogen. The Kjeldahl digestion oxidizes all Nitrogen species to Nitrates for analysis. Microbes at the POTW first nitrify to Nitrates, then denitrify to Nitrogen gas, in a two-step process that is slow and inefficient. TKN represents a significant increase in residence time at the lagoons.
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TSS means Total Suspended Solids. These are a separation problem for the pretreatment area at the water plant. Very high loadings get by the separation steps to begin filling the lagoons with silt. Eventually the lagoons will have to be dredged. The POTW apportions those costs against the TSS figure from its clients.
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Metals and Phosphates are dissolved inorganic contaminants. They are oftentimes chemically precipitated (turned to solids and then separated). Metals are environmental poisons. Phosphates are powerful fertilizers for algal growth. That's how phosphates contribute to eutrification (important to avoid in slow moving water basins). Usually a strategy to minimize either metals or phosphates will be a profitable undertaking.
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Major sources of BOD and phosphate at the meat plant are bone and its marrow, and blood. By efficiently directing these commodities to byproduct streams, you can both improve your sales there, and reduce pretreatment burden (costs) or charges from your wastewater district. Spent yeast is the biggest BOD contributor for our brewing customers.
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All proteinaceous material is the big source of TKN.
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By adopting pretreatment, you can develop a strategy to remove these wastes, often at a savings compared to your POTW charges for untreated waters.
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