MY LONG years of experience in the manufacturing industry include a stint in managing a large wastewater treatment plant (WTP). Our WTP consists of facilities for removal of solids by gravity and dissolved pollutants by biological treatment. The treated wastewater is then used for some of the mill’s requirements such as showers for some equipment and for watering plants and grasses around the mill. A network of pipes was laid out specifically for the use of wastewater for greening.
Wastewater, when treated, is a valuable resource. This is highlighted with the celebration of World Water Day last March 22, which has for its theme “Why waste water?” With the growing scarcity of clean, fresh water, the importance of treating wastewater to avoid contamination of rivers and streams where it is discharge as well as its possible re-use is brought to fore.
Wastewater is used water. It includes contaminants such as human waste, food scraps, oils, soaps and chemicals. At home, wastewater comes from sinks, showers, bathtubs, toilets, washing machines and dishwashers. Wastewater also comes from manufacturing process in commercial establishments and industries. Even the agriculture industry produces wastewater. It comes in the form of irrigation water that has been contaminated with fertilizers, herbicides and pesticides.
If wastewater is not properly treated, the environment and human health can be affected. Untreated wastewater pollutes drinking, bathing and irrigation water. Fish and other marine species die. Beaches, like the Manila Bay, when contaminated with coliform bacteria are rendered unfit for swimming. Fish and shellfish become unfit for human consumption. When biodegradable waste decays in water, it depletes oxygen supply choking marine species. Untreated wastewater also carries various diseases.
One of the United Nations’ Sustainable Development Goals is to improve water quality and reduce, treat and reuse wastewater. A recent United Nations report says that low-income countries are particularly impacted by the release of wastewater into the environment without being either treated or collected. On average, only 8 per cent of domestic and industrial wastewater is treated, compared to 70 per cent in high-income countries.
Wastewater treatment reduces pollutants in wastewater to a level that nature can handle. The Department of Environment and Natural Resources has different standards on the level of treatment required depending on where the wastewater is discharged. For instance, the degree of treatment needed for a body of water that is used for drinking or bathing is more stringent than a river that is used for irrigation purposes only. Usually, a tertiary treatment such as chlorination is required in addition to biological treatment to kill pathogens.
Next: Uses of treated wastewater