•A dynamic model describing the COD dependence of the α factor is presented here.•We added to ASM the re-calculation of air flow as function of load and O2 transfer.•The model was applied to two water reclamation plants.•The model prediction of air flow improved by 20–35% using dynamic alpha.Due to the importance of wastewater aeration in meeting treatment requirements and due to its elevated energy intensity, it is important to describe the real nature of an aeration system to improve design and specification, performance prediction, energy consumption, and process sustainability. Because organic loadings drive aeration efficiency to its lowest value when the oxygen demand (energy) is the highest, the implications of considering their dynamic nature on energy costs are of utmost importance. A dynamic model aimed at identifying conservation opportunities is presented. The model developed describes the correlation between the COD concentration and the α factor in activated sludge. Using the proposed model, the aeration efficiency is calculated as a function of the organic loading (i.e. COD). This results in predictions of oxygen transfer values that are more realistic than the traditional method of assuming constant α values.The model was applied to two water resource recovery facilities, and was calibrated and validated with time-sensitive databases. Our improved aeration model structure increases the quality of prediction of field data through the recognition of the dynamic nature of the alpha factor (α) as a function of the applied oxygen demand. For the cases presented herein, the model prediction of airflow improved by 20–35% when dynamic α is used. The proposed model offers a quantitative tool for the prediction of energy demand and for minimizing aeration design uncertainty.Download high-res image (371KB)Download full-size image

Semi-arid regions throughout the world face water scarcity and the need for more efficient and alternative sources of drinking water supply. Inland regions in the Arabian Peninsula have the alternate option of coastal seawater desalination and long-distance conveyance, often with lift to substantial elevation. In several aquifers of this region, naturally occurring radium in groundwater is above acceptable standards and must be reduced.We analyzed the energy footprint of a modular process employing a combination of pellet reactor for radium and hardness minimization, reverse osmosis with intermediate precipitation, and concentrated brine crystallization to achieve high recovery with zero liquid discharge (ZLD). Pilot tests demonstrate technical viability of the selected processes to achieve high recovery, radium and hardness reduction, and over 95% salinity reduction with zero liquid discharge. The results indicate that the energy usage per unit volume of water produced from groundwater is consistently lower than coastal seawater desalination, regardless of the conveyance distance. The substantial reduction of energy, higher recovery and minimized residual discharge of this process are also beneficial to the environment when compared to conventional processes currently being used. The results may be applicable and beneficial to other regions with similar conditions.Highlights► High-recovery groundwater desalination is key to inland water supply for arid areas. ► Coastal desalination processes need substantial lift and conveyance to inland areas. ► Inland groundwater desalination has lower energy footprint than coastal processes. ► Brine crystallization shifts concentrate from costly byproduct to mineable commodity.

•The link between aeration efficiency decrease and fouling have been modelled.•The study of the connection between biofouling and diffuser efficiency allow energy savings.•The aeration efficiency of six diffusers in two different WWTP was systematically studied.•Molecular tools were applied to model major fouling factors and energy savings.This research systematically studied the behavior of aeration diffuser efficiency over time, and its relation to the energy usage per diffuser. Twelve diffusers were selected for a one year fouling study. Comprehensive aeration efficiency projections were carried out in two WRRFs with different influent rates, and the influence of operating conditions on aeration diffusers' performance was demonstrated.This study showed that the initial energy use, during the first year of operation, of those aeration diffusers located in high rate systems (with solids retention time - SRT-less than 2 days) increased more than 20% in comparison to the conventional systems (2 > SRT). Diffusers operating for three years in conventional systems presented the same fouling characteristics as those deployed in high rate processes for less than 15 months. A new procedure was developed to accurately project energy consumption on aeration diffusers; including the impacts of operation conditions, such SRT and organic loading rate, on specific aeration diffusers materials (i.e. silicone, polyurethane, EPDM, ceramic). Furthermore, it considers the microbial colonization dynamics, which successfully correlated with the increase of energy consumption (r2:0.82 ± 7).The presented energy model projected the energy costs and the potential savings for the diffusers after three years in operation in different operating conditions. Whereas the most efficient diffusers provided potential costs spanning from 4900 USD/Month for a small plant (20 MGD, or 74,500 m3/d) up to 24,500 USD/Month for a large plant (100 MGD, or 375,000 m3/d), other diffusers presenting less efficiency provided spans from 18,000USD/Month for a small plant to 90,000 USD/Month for large plants. The aim of this methodology is to help utilities gain more insight into process mechanisms and design better energy efficiency strategies at existing facilities to reduce energy consumption.Download high-res image (290KB)Download full-size image