Water after sludge dewatering, also known as reject water from anaerobic digestion, is recycled back to the main wastewater treatment inlet in the wastewater treatment plant Porsgrunn, Norway, causing periodic process disturbance due to high ammonium of 568 (±76.7) mg/L and total chemical oxygen demand (tCOD) of 2825 (±526) mg/L. The main aim of this study was the simultaneous treatment of reject water ammonium and COD using two pilot-scale sequential moving bed biofilm reactors (MBBR) implemented in the main wastewater treatment stream. The two pilot MBBRs each had a working volume of 67.4 L. The biofilm carriers used had a protected surface area of 650 m²/m³ with a 60% filling ratio. The results indicate that the combined ammonia removal efficiency (ARE) in both reactors was 65.9%, while the nitrite accumulation rate (NAR) and nitrate production rate (NPR) were 80.2 and 19.8%, respectively. Over 28% of the reject water’s tCOD was removed in both reactors. The heterotrophic nitrification and oxygen tolerant aerobic denitrification were the key biological mechanisms found for the ammonium removal in both reactors. The dominant bacterial family in both reactors was Alcaligenaceae, capable of simultaneous heterotrophic nitrification and denitrification. Moreover, microbial families that were found with equal potential for application of simultaneous heterotrophic nitrification and aerobic denitrification including Cloacamonaceae, Alcaligenaceae, Comamonadaceae, Microbacteriaceae, and Anaerolinaceae.

Access to safe drinking water remains a fundamental issue in rural areas of Ethiopia. This study aimed to evaluate the physicochemical and bacteriological quality of drinking water at protected sources in the Farta district, South Gondar Zone, Ethiopia. The study covered 16 rural Kebeles and was conducted on 75 protected dug wells with hand pumps (HDWs) and 17 protected springs (PSs). Data were collected during the wet and dry season, and field measurement were conducted on water samples pH, turbidity, electrical conductivity, and temperature, while laboratory analysis focused on E. coli prevalence. Additionally, sanitary risk assessment was also performed. The result showed that, the pH values ranged from 5.4 to 8.1, turbidity levels varied between 0 to 100 nephelometric turbidity unit (NTU), electric conductivity ranged from 62 to 584 µS/cm, and temperature ranged from 12.1 to 27 °C. Among all the samples, 39.1% had a pH below the minimum standard value of 6.5, close to 50.5% did not meet the turbidity requirement (5NTU), and all samples were safe against electric conductivity levels. The E. coli contamination was widespread, and only a small percentage of water sources, such as 21.7% HDWs, 6.7% PSs during dry season, and 13% HDWs during wet season were negative to E. coli detection. A significant proportion of water sources, such as 18% HDWs and 13% PSs during dry season, as well as 44.9% HDWs and 46.7% PSs during wet season, fell into the high microbial health risk category. Sanitary inspections revealed that only 16.7% of water sources were classified as low sanitary risk. This study revealed that majority of water sources were unfit to drinking and may endanger the public health. To ensure safe water availability frequent cleaning and disinfection of water sources, implementation of household water treatment, and improvement of WASH (water, sanitation and hygiene) infrastructure is needed.

Several series of batch and continuous experiments were performed to investigate the removal of metformin and other contaminants from two wastewaters: wastewater I (WWI) containing 4 mg/L metformin and wastewater II (WWII) containing 110 g/L butanol. Biomethane potential (BMP) tests on WWII showed 77% of total chemical oxygen demand (tCOD = 110 g/L) degradability, and no apparent inhibition effects were observed. BMP tests on WWI showed an apparent inhibitory effect reflected in lower biogas production with increasing metformin concentration in the wastewater. Continuous flow hybrid vertical anaerobic biofilm (HyVAB^®) experiments were consistent with the batch test findings. It was necessary to co-digest WWI (metformin) with WWII (easily degradable organics) to achieve complete metformin removal. After a period of adaptation, WWI and WWII co-digestion achieved up to 98% tCOD removal and 100% metformin removal. Most of the contaminants were removed in the anaerobic section of the HyVAB^®, which implies that higher chemical oxygen demand (COD) loads than tested here are possible, given some optimization. The pilot reactor was able to manage organic loads of 11 g COD/d and above 10 mg/L metformin with a removal of 98% and 100% for tCOD and metformin, respectively.

Removing ammonium via the partial nitritation anammox (PNA) process has been widely applied because of its cost and energy effectiveness. However, the first stage of PNA, partial nitritation, is hard to implement practically due to the challenging suppression of nitrate oxidizing bacteria (NOB) and should be achieved in the anammox environment to extend it to one stage PNA. Hence, this article evaluates different techniques, such as the combination of low dissolve oxygen (DO) and high free ammonia (FA), and the intermittent aeration cycle to achieve partial nitritation in an anammox start-up environment. For this purpose, a 10.5 L lab-scale moving bed biofilm reactor was set up and fed with synthetic wastewater and the transformation of influent ammonium into nitrate and nitrite was measured. The results showed that, despite applying low DO and higher free ammonia than the inhibition range of NOB, the nitrate production rate (NPR) was consistently higher than the nitrite accumulation rate (NAR), signifying no sufficient NOB suppression, partial nitritation under continuous aeration and up to a 0.27 gN/m²·d surface ammonium loading rate (SALR). Higher SALR than 0.27 gN/m²·d could result in partial nitritation since nitrogen compounds transformation was closer to partial nitritation when the reactor was subjected to 0.27 gN/m²·d rather than 0.14 gN/m²·d. Lifting up the SALR, on the other hand, results in a bad anammox environment and cannot prolong it to one-stage PNA. An intermittent aeration cycle with four different cycle lengths sets, obtained by monitoring nitrogen compound transformation, was, therefore, applied to the reactor. The relatively shorter aerobic length of 10 min ON and 30 OFF intermittent aeration cycle with 0.5 mg/L aerated DO was successful in achieving the partial nitritation with NPR, NAR, and ammonium removal efficiency (ARE) values of 17%, 78%, and 37%, respectively, showing that shorter aerated length suppresses NOB to a high degree due to less available time for NOB after oxygen starvation.

Conventional biofilm reactors are widely used for the removal of organic constituents and nutrients (i.e., nitrogen and phosphorus) in municipal and industrial wastewater treatment. Moving bed biofilm reactor (MBBR) and continuously flow intermittent cleaning reactor (CFIC) have been developed as more compact, small footprint, and highly efficient biofilm-based systems for wastewater treatment. However, despite the advancements in reactor technology, there is limited scientific information on the microbial composition of the biofilms in these systems. This study aimed to characterize and provide early insights into the microbial diversity of biofilms grown on biofilm carriers and liquid suspensions of the biofilm-based wastewater treatment systems. Microbial samples were collected from biofilm carriers and liquid suspension in four full-scale MBBR plants and two CFIC plants in Norway, all treating municipal and industrial wastewater. DNA was extracted from the samples and subjected to meta-barcode sequencing for taxonomic classification of microbial communities in each treatment plant. The results revealed significant variation in microbial compositions across treatment plants, influenced by wastewater characteristics, biofilm carrier types, and reactor operational characteristics. On the biofilm carriers, the dominant bacterial taxa included TM7-1 (Saccharibacteria), Burkholderiales, Clostridiales, Actinomycetales, Pseudomonadales, Rickettsiales, and Rhodobacteriales. In liquid suspensions, the dominant groups were Clostridiales, Methanosarcinales, Pseudomonadales, Flavobacteriales, and Rhodobacteriales. In conclusion, this study highlights the diverse microbial populations on biofilm carriers and liquid suspensions, which collectively contribute to the enhanced treatment efficiency of both MBBR and CFIC systems.