An integrated physical-chemical system for concurrent carbon, nitrogen, and phosphorus removal in municipal wastewater treatment plants.

A substantial quantity of suspended solids (SS) present in municipal wastewater leads to the swift depletion of the ion exchange (IE) capacity of natural zeolites like Clinoptilolite (CIO). This limitation has become the primary factor contributing to the limited adoption of the IE technique within municipal wastewater treatment plants (WWTPs). However, an extensive lab-scale and pilot-scale study conducted over approximately one year has made it possible to efficiently apply the IE system using CIO (main grain size of 0.5-1.0 mm) upstream of the primary sedimentation tank (PST). The primary treated wastewater (PTWW) was introduced to the IE system either by pre-straining or without any pre-treatment. The IE system's capabilities for removing total suspended solids (TSS), chemical oxygen demand (COD), and phosphorus (P) while primarily focusing on ammonium (NH4+) recovery were undergone for a detailed investigation. Frequent backwashing, involving intermittent water and air injection, was used to mitigate clogging as the main problem of the IE system for treating PTWW. The results revealed a mean removal efficiency of 85 %, 60 %, 50 %, and 30 % for NH4+, TSS, TCOD, and total phosphorus (TP), respectively, per cycle exclusively for the IE system. As the system scaled up, a substantial reduction was observed in the adsorption capacity, shifting from approximately 12 to 1 g NH4+ (kgCIO)-1. Despite this drawback, the study's finding showed that prolonged treatment of PTWW for NH4+ removal and recovery in municipal WWTPs, besides substantially reducing carbonaceous pollutants, is applicable. Implementing this application will not only decrease the biological treatment costs for municipal wastewater but also yield valuable by-products, such as NH4Cl, which can serve as a foundational material for the production of ammonium chloride fertilizer. Therefore, transitioning to IE systems in municipal WWTPs will diminish the reliance on resource-intensive methods like the Harber-Bosch procedure for producing nitrogen fertilizer.

Performance evaluation and siting index of the stabilization ponds based on environmental parameters: a case study in Iran.

Stabilization ponds are open pools that remove total suspended solids, organic matters, microbial and pathogenic agents using physical, chemical, and biological processes. If the stabilization ponds are not well designed, they can produce odors, breed many insects, increase suspended solids concentration in the effluent and pollute groundwater. Consideration of environmental factors is critical for operation and maintenance. In this study, first, information on wastewater treatment plants and meteorological parameters were collected, and simultaneously, specialists were selected to score the effect of environmental factors on stabilization pond efficiency. A geographic information system was used to sit for suitable locations for stabilization ponds. The results showed that 23.6 % of Iran's treatment plants are stabilization ponds, which based on climate, evaporation, sunny hours, ice days, wind speed, and temperature parameters, 33.33 %, 37.3 %, 14 %, 50 %, 64 and 26 % of the stabilization ponds have obtained good points, respectively. The results also showed that 50 % of the stabilization ponds obtained an acceptable score considering all environmental parameters' simultaneous effect. A preliminary study based on considering all the environmental parameters showed that the central and southern regions are the best areas for establishing waste stabilization ponds; in contrast, northern and northeastern regions can have high operation and maintenance costs with lower efficiency. This study has shown that setup and design of the new waste stabilization ponds in Iran need to take into account by considering environmental factors because these factors have the main effect on algae growth which are one of main biological treatment.