Investigating factors affecting energy consumption in rural Alaskan water treatment and distribution systems, and exploring energy-saving strategies for wastewater treatment in cold climates

Abstract

Underlying permafrost in rural and remote Alaskan communities creates difficulties in connecting these communities to the electrical grid, resulting in the import of fuel from nearby cities by air or barge for electricity generation. During the winter months, a large amount of fuel and electricity is required for water treatment and distribution in these communities to keep the water temperature above freezing. Furthermore, domestic wastewater in rural Alaska is treated within wastewater lagoons, which lose their treatment efficiency during the freezing winter months. In contrast, the biological aerated filter (BAF), which has become an efficient alternative for domestic wastewater treatment in off-grid houses, consumes higher energy in the form of continuous aeration. As a result, residents living in rural Alaska pay significantly higher utility costs compared to the national average. This study is designed with two goals, to determine the factors contributing to higher energy consumption for water treatment and distribution and to evaluate energy consumption and BAF performance for wastewater treatment at different aeration regimes. The overall study is based on the following two hypotheses: (i) factors including seasonal changes, geographical regions, population size, and water distribution system (WDS) types influence energy consumption for water treatment and distribution, and (ii) intermittent aeration saves energy without impacting BAF performance for wastewater treatment. After analyzing energy audit data from the Alaska Native Tribal Health Consortium (ANTHC) for 78 rural Alaskan communities, we found that average per capita energy consumption was highest in interior Alaska (1826 kWh), followed by Northern (917 kWh), Southwestern (660 kWh), Gulf Coast (492 kWh), and Southeastern (136 kWh) regions. Among the water distribution system (WDS) types, piped circulating systems showed the highest energy consumption (1100 kWh), followed by washeteria (1000 kWh), closed hauling (800 kWh), individual wells (550 kWh), and piped pressure (300 kWh) systems. In the BAF experiment, we operated a bench-scale BAF at continuous and intermittent aeration regimes (1 hour on/1 hour off, and 2 hours on/2 hours off) using synthetic wastewater and evaluated the treatment efficiency in terms of chemical oxygen demand (COD) removal. The results showed similar COD removal rates for continuous aeration (67.6%), 1 hour on/1 hour off (66.5%), and 2 hours on/2 hours off (63.4%) aeration regimes. Additionally, we found that intermittent aeration regimes consumed significantly less energy than continuous aeration. This research helps to understand energy consumption for water treatment and distribution in rural Alaskan communities and provides a potential energy-saving approach for treating wastewater in Arctic communities.