Research aim in this paper is, use of treated domestic wastewater in cement and fly ash mortar. Zero discharge domestic wastewater treatment plants were constructed in Vishnu Education Society, Bhimavaram, W.G, Dist, A. P, India. One of the treatment plants has been treating 250 kL/day of domestic wastewater. After biological treatment, wastewater was treated in sand filter followed by carbon filter. In the present work, cement was partially replaced with fly ash. The best strength was obtained in a combination of 30% Fly ash + 70% Cement i.e., denoted by M4 mix. Treated domestic wastewater was used as mixing water in M4 mix. The effect of treated domestic wastewater (T) on fresh and hardened state of M4 mix mortar properties was studied in laboratory and same compared with mortar cubes made with distilled water (D). Cubes made with T or D mixing water in M4 mix were exhibited almost same performance in fresh, hardened properties. And also evaluated durability performance of M4 + D, and M4 + T samples in non-water environment friendly. X-ray diffraction and SEM techniques were employed to encounter compounds formed during the hydration process of cement and fly ash with D and T.