Groundwater Quality in Indonesia's Big Cities is Getting Worse
One of the study authors from ITB, Dasapta Erwin Irawan, explained that he and his colleagues tried to compare the quality of groundwater and river water in big cities in Indonesia, such as on the banks of the Cikapundung River in Bandung; Sumpil River and Jilu River in Malang, East Java; and the Ciliwung River in West Java-DKI Jakarta.
As a result, all groundwater in the area has almost the same quality as river water. They found groundwater's total dissolved solids (TDS) were as high as river water. TDS is used as an indicator of pollution level because it can reflect how much element content, including metal elements.
The higher the TDS value, the higher the water pollution. The TDS value in groundwater in the Cikapundung River (Bandung), Ciliwung River (Jakarta), and Cisadane River (Banten) can approach 1000 ppm. Meanwhile, TDS in springs ranges from 100-500 ppm.
The similarity of groundwater and river water quality is very likely due to the mixing of the two in the Hyporeic Zone at the bottom of the river. In this zone, water quality is exchanged from the river into the aquifer (water-carrying layer) and vice versa. This exchange also brings chemical to organic elements, including bacteria and viruses, contained in river water to groundwater, and vice versa.
This exchange process becomes faster due to a large number of groundwater pumping activities along the riverbanks. As a result, river water is sucked in and impacts the widening of the Hyporeic Zone towards the mainland.
Triggers for Worse Water Quality
Human activities on the surface also affect the quality of groundwater, such as the disposal of household waste containing organic matter directly into the gutter, causing an increase in the content of bacteria such as E-coli, nitrite compounds, and nitrates in the water. The water in the ditch flows into the river, and some seeps into the ground.
In addition, poor groundwater quality is also caused by increasing urbanization in Indonesia's big cities. This urbanization triggers many slum settlements that often throw waste into the river. It is where groundwater begins to become contaminated.
The government has actually tried to improve the riverbanks, including prohibiting factory waste into the river. Erwin said that to maintain water quality, the prohibition of direct disposal of industrial and household waste into public sewers must be encouraged.
"Real estate developers can build sewage treatment systems or install grease traps in the houses they build," Erwin wrote in The Conversation.
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