Sand filters for removal of microbes and nutrients from wastewater during a one-year pilot study in a cold temperate climate

Response of greenhouse gas emissions and microbial community dynamics to temperature variation during partial nitrification.

Aims: This study was conducted to evaluate the performance of a novel horizontal subsurface flow wetland (HSFW) in naturally improving the dissolved oxygen (DO) and the impact on redox condition, microbial activity and the nitrogen removal in the HSFW bed. Materials and methods: The HSFW, equipped with cascaded natural aeration ditches (NADs), was the second stage of a hybrid constructed wetland (CW) after vertical-baffled flow wetland beds. The performances of the HSFW for organics and nitrogen removal in a full-scale hybrid CW system treating municipal wastewater for more than three years have been analysed. The spatial distributions of the oxidation-reduction potential (ORP), DO, microbial population density and specific oxygen uptake rate were determined, and their correlations were analysed in one selected section of the HSFW bed. Results: A 7-m-long shallow NAD increased the DO concentration from 0.28 mg O2 l−1 to 3.80 mg O2 l−1 and the ORP from+37.3 mV to+247.7 mV, creating an aerobic zone with a h...

Variation of dissolved oxygen and redox potential and their correlation with microbial population along a novel horizontal subsurface flow wetland

Removal of acidic pharmaceuticals within a nitrifying recirculating biofilter.

Waste management practices currently employed in many rural Alaska communities are potentially contributing to human and environmental health impacts, and this problem may be exacerbated with the anticipated warming climate. For rural communities, factors that contribute to insufficient waste management practices include climate and environmental conditions, limitation of federal and state capital funding for construction, and the continuing financial burden associated with providing adequate operations and maintenance. As a response, federal regulatory exemptions are granted for construction and design of solid waste sites and limited state regulations are in place for wastewater discharge criteria. Due to the absence of proper site assessment and monitoring, very little is known about the fate and transport of point source pollutants arising from these wastewater and solid waste sites. Moreover, these fate and transport processes may be susceptible to changes resulting from human activity or a warming climate. Thus, this knowledge gap associated with waste-related pollutants in rural Alaska could obscure potential threats to human and environmental health by concealing impacts to freshwater systems. This research was intended to achieve a better understanding of rural Alaska waste leachate compositions by evaluating contaminant prevalence and diversity, quantifying contaminant concentration levels, and evaluating their potential migration into nearby freshwater systems. Over the course of three years, waste sites at five rural Alaska communities were sampled and tested for heavy metals, organic constituents, and microbial indicator organisms. The purpose of the analysis was to evaluate the impact of waste sites on soil, surface, and subsurface waters in the vicinity of the sites. The resulting findings are assembled into three chapters describing 1) the assessment of heavy metal leachate in rural Alaska solid waste sites, 2) the identification of new emerging organic pollutants in rural Alaska waste sites, and 3) the partitioning and transport behavior of pathogen indicator organisms in cold regions. The research outcome of E.coli and Enterococcus sp. were observed in waste impacted water and soil samples, heavy metal migration into nearby freshwaters, and pharmaceuticals, phthalates, and benzotriazole in waste impacted water samples. The research findings highlight the need to apply state regulations to remove potentially hazardous components from rural Alaska wastewater and municipal solid waste streams. Additionally, there is a need to establish effective solid waste and wastewater leachate monitoring and assessment strategies for active and closed rural Alaska waste sites.

Assessment of contaminant concentrations and transport pathways in rural Alaska communities' solid waste and wastewater sites

Household on-site septic systems with secondary wastewater treatment in Anchorage, Alaska, were sampled and analyzed for performance parameters during the winter to spring months. System types included intermittent dosing sand filters (ISF), three types of recirculating trickling filters (RTF), and suspended-growth aeration tanks. Total nitrogen from the trickling filter and aeration tank effluent was fairly uniform, at approximately 30 mg/L. Total suspended solids (TSS) means were mostly less than 15 mg/L. The 5-day biochemical oxygen demand (BOD 5 ) showed considerable variability, with means ranging from 9.2 mg/ L for ISFs up to 39.5 mg/L for one type of RTF, even though this type has shown excellent results in several test programs. The data suggested that effluent temperature within the sample range had almost no effect on effluent concentrations of BOD 5 or TSS and only a small effect on the removal of total nitrogen. Non-climatic factors were probably of equal importance to treatment results.

Eric Williamson

Papers

Cold climate performance analysis of on-site domestic wastewater treatment systems.