By Marcus Gay, NM WRRI Student Program Coordinator
In places like southern New Mexico, which are vulnerable to water shortages and droughts due to water scarcity, it is important to explore alternative water sources to achieve sustainable water management. Wastewater treatment facilities in water-stressed regions are considering reusing treated urban wastewater as an option to reduce freshwater demand. Possible reuse applications of treated urban wastewater include non-food irrigation like landscaping, and recreational areas where human exposure is restricted. EPA guidelines require that treated water must be disinfected prior to reuse. Traditionally, chlorine has been used for disinfecting the wastewater for microbial safety to prevent bacterial regrowth. However, chlorination can result in the production of disinfection by-products (DBPs), which are recognized as a health hazard.
A novel algal wastewater treatment system (A-WWTS) developed at New Mexico State University (NMSU) is being demonstrated at the Las Cruces Wastewater Treatment Plant, and it is hypothesized that the inherent disinfection capability of this system can be beneficial in reducing the final disinfectant demand and the potential for DBP formation. This is the focus of Srimali Munasinghe-Arachchige’s research. Srimali, a PhD candidate in the Civil Engineering Department at NMSU, plans to track nitrosamines, a carcinogenic category of DBP, in the chlorinated algal effluent. Srimali received an NM WRRI Student Water Research Grant for her project entitled, Assessment of Disinfection Byproducts (DBPs) formation in algae-treated wastewater for safer reuse in restricted applications. The specific goals of this project are to track nitrosamines formation potential in the chlorinated algal effluent, determine the pH condition and minimum chlorine dosage, and to compare the chlorinated effluent of A-WWTS with the guidelines for restricted reuse.
This study consisted of two experiments. First, analyzing the maximum variations in water quality parameters due to chlorination of the algal effluent, where preliminary results indicate a low potential for DBP formation in the effluent of A-WWTS. The second experiment was to determine operating conditions for chlorination of the algal effluent. Preliminary results of this study suggest that adjusting pH to six prior to chlorination would reduce DBP formation. However, further experiments are necessary to confirm the results.
The results of this project will be beneficial to wastewater utilities by providing information about sustainable utility services. As Srimali explains, “Based on the preliminary findings, the algal effluent can be seen to have the potential to yield low-cost, high quality reclaimed water for safe reuse in restricted applications reducing the demand for the limited freshwater supplies.”
Srimali received a Bachelor of Science degree from the University of Peradeniya, in her home country of Sri Lanka where she specialized in Chemical and Process Engineering. She then earned a Master of Science degree in 2018 from NMSU in Environmental Engineering. Under the guidance of her faculty advisor, Dr. Nagamany Nirmalakhandan, Srimali now works on recovering nitrogen from wastewater via gas-permeable membranes to produce fertilizer and multi-criteria decision-making methods to identify preferred options for wastewater treatment. After graduation in the fall, Srimali is planning on a career related to the water or wastewater sector. As an Environmental Engineer, Srimali is interested in water conservation and reuse to contribute to the betterment of humans while preserving the environment.