4AE3 U5 C3 Obj 5.pdf

Liquid and Solid Emissions • Chapter 3 Objective 5 Describe the preventive measures that can be taken to prevent liquid and thermal pollution. Preventive Measures – Liquid Pollution Liquid wastes are not pollutants, unless they escape containment, enter the environment, and cause adverse effects....

Liquid and Solid Emissions • Chapter 3 Objective 5 Describe the preventive measures that can be taken to prevent liquid and thermal pollution. Preventive Measures – Liquid Pollution Liquid wastes are not pollutants, unless they escape containment, enter the environment, and cause adverse effects. Proper treatment before the liquid waste enters the environment can prevent pollution. Occasionally, effluent can be cleaned up to the point that part of it can be reused rather than dumped. This process also reduces the amount of fresh source water required. Some plants, notably in the pulp and paper and oil sand industries, are now being designed so that most or all of their wastewater can be reused, producing “near zero effluent.” The following principles and devices can be used to reduce the effects of liquid pollution: • • • • pH control settling ponds vacuum filters grease traps pH Control Effluents dumped into an existing stream should have a similar pH value to the receiving water. A deviation from this existing pH can damage life in the stream. Industries generating strongly alkaline or acidic effluents must neutralize the effluent before it is released. Even within cities or municipalities with common sewer collection systems, companies are required to maintain their wastewater discharge between given pH values. Sewer line sampling monitors can detect sources of pH deviation. Fines are levied against the offenders. Companies that produce high or low pH waste streams monitor and neutralize their effluent before it enters the sewer system or waterway. One common method of control uses a dilution tank or pond. If monitors detect a surge of acid, a chemical pump adds enough alkaline material to bring the effluent back to the desired pH. If the system shows an alkaline deviation, an acid pump is used to bring the pH under control. When the flow is neutralized, it can be discharged. Settling Ponds Some industries discharge particulate laden water from the process. In years past, it was common practice to dump the discharge into the nearest body of water and forget about it. The downstream effects did not concern management. However, through responsible management, regulatory requirements, and environmental awareness, this practice has rapidly changed. One method that improves this problem is the use of settling ponds or tanks. Effluent is allowed to flow slowly through a settling pond, where particulate matter settles to the bottom. The clean effluent is then dumped into the body of water. Very fine particles or those in colloidal solution are too small to settle out in a settling pond. Industries that generate large quantities of colloidal material must use coagulants to help cluster these small particles together so that they will settle. This process is also used in some water supplies to cause accelerated settling of fine material. 4th Class Edition 3 • Part A 3-13