Estimating the financial costs of sanitation systems

Estimating the financial costs of sanitation system

Nitrogen Removal from Wastewater by Coupling Anammox and Methane-Dependent Denitrification in a Membrane Biofilm Reactor

This work demonstrates, for the first time, the feasibility of nitrogen removal by using the synergy of anammox and denitrifying anaerobic methane oxidation (DAMO) microorganisms in a membrane biofilm reactor (MBfR). The reactor was fed with synthetic wastewater containing nitrate and ammonium. Methane was delivered from the interior of hollow fibres in the MBfR to the biofilm that grew on the fiber’s outer wall. After 24 months of operation, the system achieved a nitrate and an ammonium removal rate of about 190 mgN L^–1 d^–1 (or 86 mgN m^–2 d^–1, with m² referring to biofilm surface area) and 60 mgN L^–1 d^–1 (27 mgN m^–2 d^–1), respectively. No nitrite accumulation was observed. Fluorescence in situ hybridization (FISH) analysis indicated that DAMO bacteria (20–30%), DAMO archaea (20–30%) and anammox bacteria (20–30%) jointly dominated the microbial community. Based on the known metabolism of these microorganisms, mass balance, and isotope studies, we hypothesize that DAMO archaea converted nitrate, both externally fed and produced by anammox, to nitrite, with methane as the electron donor. Anammox and DAMO bacteria jointly removed the nitrite produced, with ammonium and methane as the electron donor, respectively. The process could potentially be used for anaerobic nitrogen removal from wastewater streams containing ammonium and nitrate/nitrite

Removal of the X‑ray Contrast Media Diatrizoate by Electrochemical Reduction and Oxidation

Due to their resistance to biological wastewater treatment, iodinated X-ray contrast media (ICM) have been detected in municipal wastewater effluents at relatively high concentrations (i.e., up to 100 μg L^–1), with hospitals serving as their main source. To provide a new approach for reducing the concentrations of ICMs in wastewater, electrochemical reduction at three-dimensional graphite felt and graphite felt doped with palladium nanoparticles was examined as a means for deiodination of the common ICM diatrizoate. The presence of palladium nanoparticles significantly enhanced the removal of diatrizoate and enabled its complete deiodination to 3,5-diacetamidobenzoic acid. When the system was employed in the treatment of hospital wastewater, diatrizoate was reduced, but the extent of electrochemical reduction decreased as a result of competing reactions with solutes in the matrix. Following electrochemical reduction of diatrizoate to 3,5-diacetamidobenzoic acid, electrochemical oxidation with boron-doped diamond (BDD) anodes was employed. 3,5-Diacetamidobenzoic acid disappeared from solution at a rate that was similar to that of diatrizoate, but it was more readily mineralized than the parent compound. When electrochemical reduction and oxidation were coupled in a three-compartment reactor operated in a continuous mode, complete deiodination of diatrizoate was achieved at an applied cathode potential of −1.7 V vs SHE, with the released iodide ions electrodialyzed in a central compartment with 80% efficiency. The resulting BDD anode potential (i.e., +3.4–3.5 V vs SHE) enabled efficient oxidation of the products of the reductive step. The presence of other anions (e.g., chloride) was likely responsible for a decrease in I^– separation efficiency when hospital wastewater was treated. Reductive deiodination combined with oxidative degradation provides benefits over oxidative treatment methods because it does not produce stable iodinated intermediates. Nevertheless, the process must be further optimized for the conditions encountered in hospital wastewater to improve the separation efficiency of halide ions prior to the electrooxidation step

A Systematic Laboratory Testing of Concrete Corrosion Resistance in Sewers

This chapter developed a Systematic COrrosion REsistance (SCORE) testing to determine the concrete corrosion resistance in urban wastewater systems, primarily sewers. Microbially induced concrete corrosion has a profound impact on the useful service life of concrete sewers, which leads to billions of dollars of economic loss annually. Concrete is widely used in the rehabilitation or construction of new wastewater infrastructure. It is vital to quantitatively measure the corrosion resistance for a reliable and sustainable design. The testing of corrosion resistance is primarily based on the measurements of initiation time and corrosion rate, in combination with corrosion development parameters including surface pH, sulfur compounds, and sulfide uptake rate. The different corrosion parameters support each other to make a cohesive comparison of different concrete products. Two newly developed Calucem concrete products were demonstrated with different corrosion resistance using this testing approach. In addition, advanced microscopic methods and microbial community analysis will help to optimize the concrete design by providing insights into the corrosion resistance. The systematic testing approach has been applied in large-scale concrete sewers and showed its effectiveness in supporting the service life design

Effects of Surface Charge and Hydrophobicity on Anodic Biofilm Formation, Community Composition, and Current Generation in Bioelectrochemical Systems

The focus of this study was to investigate the effects of surface charge and surface hydrophobicity on anodic biofilm formation, biofilm community composition, and current generation in bioelectrochemical systems (BESs). Glassy carbon surfaces were modified with −OH, −CH₃, −SO₃^–, or −N⁺(CH₃)₃ functional groups by electrochemical reduction of aryl diazonium salts and then used as anodes with poised potential of −0.2 V (vs Ag/AgCl). The average startup times and final current densities for the −N⁺(CH₃)₃, −OH, −SO₃^–, and −CH₃, electrodes were (23 d, 0.204 mA/cm²), (25.4 d, 0.149 mA/cm²), (25.9 d, 0.114 mA/cm²), and (37.2 d, 0.048 mA/cm²), respectively. Biofilms on different surfaces were analyzed by nonturnover cyclic voltammetry (CV), fluorescence in situ hybridization (FISH), and 16S rRNA gene amplicon pyrosequencing. The results demonstrated that 1) differences in the maximum current output between surface modifications was correlated with biomass quantity, and 2) all biofilms were dominated by <i>Geobacter</i> populations, but the composition of −CH₃-associated biofilms differed from those formed on surfaces with different chemical modification. This study shows that anode surface charge and hydrophobicity influences biofilm development and can lead to significant differences in BESs performance. Positively charged and hydrophilic surfaces were more selective to electroactive microbes (e.g<i>. Geobacter</i>) and more conducive for electroactive biofilm formation

Evaluation of continuous and intermittent trickling strategies for the removal of hydrogen sulfide in a biotrickling filter

Biotrickling filter (BTF) is a widely applied bioreactor for odour abatement in sewer networks. The trickling strategy is vital for maintaining a sound operation of BTF. This study employed a lab-scale BTF packed with granular activated carbon at a short empty bed residence time of 6 s and pH 1–2 to evaluate different trickling strategies, i.e., continuous trickling (different velocities) and intermittent trickling (different trickling intervals), in terms of the removal of hydrogen sulfide (H2S), bed pressure drop, H2S oxidation products and microbial community. The H2S removal performance decreased with the trickling velocity (∼3.6 m/h) in BTF. In addition, three intermittent trickling strategies, i.e., 10-min trickling per 24 h, 8 h, and 2 h, were investigated. The H2S elimination capacity deteriorated after about 2 weeks under both 10-min trickling per 24 h and 8 h. For both intermittent (10-min trickling per 2 h) and continuous trickling, the BTF exhibited nearly 100 % H2S removal for inlet H2S concentrations<100 ppmv, but intermittent BTF showed better removal performance than continuous trickling when inlet H2S increased to 120–190 ppmv. Furthermore, the bed pressure drops were 333 and 3888 Pa/m for non-trickling and trickling periods, respectively, which makes intermittent BTF save 83 % energy consumption of the blower compared with continuous tirckling. However, intermittent BTF exhibited transient H2S breakthrough (<1 ppmv) during trickling periods. Moreover, elemental sulfur and sulfate were major products of H2S oxidation and Acidithiobacillus was the dominant genus in both intermittent and continuous trickling BTF. A mathematical model was calibrated for the intermittent BTF and a sensitivity analysis was performed on the model. It shows mass transfer parameters determine the H2S removal. Overall, intermittent trickling strategy is promising for improving odour abatement performance and reducing the operating cost of the BTF

High Acetic Acid Production Rate Obtained by Microbial Electrosynthesis from Carbon Dioxide

High product specificity and production rate are regarded as key success parameters for large-scale applicability of a (bio)­chemical reaction technology. Here, we report a significant performance enhancement in acetate formation from CO₂, reaching comparable productivity levels as in industrial fermentation processes (volumetric production rate and product yield). A biocathode current density of −102 ± 1 A m^–2 and an acetic acid production rate of 685 ± 30 (g m^–2 day^–1) have been achieved in this study. High recoveries of 94 ± 2% of the CO₂ supplied as the sole carbon source and 100 ± 4% of electrons into the final product (acetic acid) were achieved after development of a mature biofilm, reaching an elevated product titer of up to 11 g L^–1. This high product specificity is remarkable for mixed microbial cultures, which would make the product downstream processing easier and the technology more attractive. This performance enhancement was enabled through the combination of a well-acclimatized and enriched microbial culture (very fast start-up after culture transfer), coupled with the use of a newly synthesized electrode material, EPD-3D. The throwing power of the electrophoretic deposition technique, a method suitable for large-scale production, was harnessed to form multiwalled carbon nanotube coatings onto reticulated vitreous carbon to generate a hierarchical porous structure