Utilization of treated wastewater from sewage treatment plants as a replacement for potable water in concrete mix

With only 0.5% of Earth’s water being potable and increasing demand driven by urbanization and construction, there is an urgent need to identify sustainable alternatives to freshwater for concrete production. This study examines the use of purified sewage water from a 10 million liters-per-day sewage treatment plant at Bambianwali, which employs sequential batch reactor technology, as a substitute for potable water in concrete mixing. An extensive analysis was conducted over a 3-year period (2021 – 2023) to evaluate the suitability of treated sewage water for concrete production. Water quality parameters analyzed included pH, temperature, total suspended solids, chemical oxygen demand, biological oxygen demand, fecal coliform, and total Kjeldahl nitrogen. Plain cement concrete cubes were prepared and tested for compressive strength using three different water mixtures: 100% potable water, a 60:40 mixture of primary treated wastewater and potable water, and a 60:40 mixture of secondary treated wastewater and potable water. After 28 days of curing, the concrete cubes prepared with secondary treated wastewater in a ratio of 60:40 achieved a characteristic strength of 22.03 N/mm2, compared to 23.96 N/mm2 for cubes made with 100% potable water. In contrast, cubes made with primary treated wastewater showed a reduced strength of 17.30 N/mm2. These findings indicate that secondary treated sewage water can serve as a feasible substitute for potable water in concrete mixing, though the compressive strength of resulting concrete may vary depending on the extent of treatment applied to the water.