Characteristics of Wastewater in a Distilleryby Ronny Kalyango
The type of wastewater coming out of a distillery depends on the type of alcohol produced, the processes followed in making the wine and the type of additives used. The volume of wastewater generated from a distillery is usually about 10 times that of ethanol produced. The characteristics of the wastewater make it cause a few problems with its utilization.
Wastewater from distilleries contains large amounts of organic and inorganic content. This makes it have extremely high chemical oxygen demand (COD) and biochemical oxygen demand (BOD). This is in addition to having a strong odor and dark brown color. It contains nutrients such as nitrogen, phosphorus and potassium. These can cause eutrophication of water bodies. This is why water bodies polluted with wastewater from distilleries have little aquatic life.
Wastewater contains a high volume of highly acidic material that presents a lot of disposal and treatment problems. On average, it usually has a pH of 3.8 – 4.4 and this is due to acidic contents such as calcium carbonate. This makes the wastewater corrosive to tanks in which it is stored or pipes through which it flows. The acidic waste water causes soil leaching and also interferes with the pH of the soil it washes over. If released untreated into rivers and other water bodies, it can cause death or migration of some organisms. The acidity also makes the recycling process more expensive.
Molasses Spent Wash (MSW)
Molasses-based distilleries release effluent that contains large amounts of dark brown colored molasses spent wash (MSW). This waste product pollutes the environment in two major ways. First, the dark colored nature of the molasses spent wash blocks out the sunlight on rivers and streams, interfering with normal processes of photosynthesis. This reduces the oxygenation of the water and leads to the death of aquatic life. The molasses spent wash also has a high pollution load which results in eutrophication of contaminated water sources. This waste product makes the rivers and canals produce an obnoxious smell since it contains putriciable organics such as skatole, indole and other sulfur compounds.
Waste water from distilleries has a pH range of 3.8 to 4.4 with calcium carbonate content of 8000-16000 mg/L. The total amount of solids in mg/L is between 60,000 to 90,000, with total suspended solids (2,000-14,000mg/L) and total dissolved solids (58,000-76,000 gm/L). The chemical oxygen demand (COD) varies between 70,000 to 98,000mg/L and biochemical oxygen demand (BOD) measured for 5 days at 200C was found to be 45,000-60,000 mg/L. Waste water also contains nitrogen (1,000-1,200mg/L), phosphate (500-1,500mg/L) and potash (5,000-12,000mg/L).
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