Hybrid osmotically assisted reverse osmosis and reverse osmosis (OARO-RO) process for minimal liquid discharge of high strength nitrogenous wastewater and enrichment of ammoniacal nitrogen

Ammoniacal nitrogen (NH4N) is a ubiquitous nitrogen pollutant found in wastewater, which could cause eutrophication and severe environmental stress. It is therefore necessary to manage NH4N by enrichment and recovery for potential reuse, as well as to regulate the amount of environmental discharge. Hybridization of membrane-based processes is an attractive option for further enhancing water and nutrient reclamation from waste streams; thus, in this present work, a hybrid osmotically assisted reverse osmosis (OARO) and reverse osmosis (RO) process was demonstrated for subsequent ammoniacal nitrogen enrichment and wastewater discharge management. Using a commercially-available cellulose triacetate membrane module, model and real wastewater containing approximately 4,000ppm NH4N were effectively dewatered and enriched to a final NH4N content of 40,300ppm. This corresponds to enrichment of around 10 times and approximately 90% pure water recovery. The effective combination of both processes resulted in high efficiency, as well as economical and energy-saving benefits, as shown by the process performance and our preliminary techno-economic analysis. The specific energy consumption of the hybrid process projected to operate at a capacity of 2,000 m3h-1 was determined to be 8.8kWh m-3, or 0.56kWh kg-1 NH4Cl removed/recovered for an initial feed solution containing around 15,300ppm NH4Cl. Hybrid OARO and RO operation was able to achieve satisfactory enrichment by the OARO process and obtaining clean water by the RO process. The hybrid OARO-RO process has shown great potential as a suitable end-stage membrane-based process for wastewater dewatering and NH4N enrichment and recovery toward a circular economy and environmental management, as well as clean water recovery.

Optimizing leachate treatment with titanium oxide-impregnated activated carbon (TiO2@ASC) in a fixed-bed column: characterization, modeling, and prediction study

This research focused on the application of a fixed bed column filled with immobilized titanium oxide-loaded almond shell carbon (TiO2@ASC) for the treatment of leachate. The adsorption performance of synthesized TiO2@ASC in fixed bed column is analyzed using adsorption experiments and modeling study. The characteristics of synthesized materials are determined by several instrumental techniques like BET, XRD, FTIR, and FESEM-EDX. The flow rate, initial concentration of COD and NH3-N, and bed height were optimized to determine the effectiveness of leachate treatment. The linear bed depth service time (BDST) plots equations with a correlation coefficient of greater than 0.98 confirmed the model's accuracy for COD and NH3-N adsorption in column structure. The adsorption process was found to be well predicted by an artificial neural network (ANN) model with a root mean square error of 0.0172 and 0.0167 for COD and NH3-N reduction, respectively. The immobilized adsorbent was regenerated using HCl and was found to be reusable for up to three cycles, promoting material sustainability. This study is aimed to contribute towards SDG 6 and SDG11 by United Nations Sustainable Development Goals.

Combined application of microbes immobilized carbon reactor and the reactive struvite system for the management of tannery deliming wastewater

This present study investigated the removal of COD and ammoniacal nitrogen (NH₄⁺-N) from tannery deliming wastewater (TDLWW) through microbes immobilized carbon consisted a bioreactor (MICCR) and reactive struvite crystallization process. Initially, 90% of the organic content of TDLWW was removed using a MICCR reactor at 24 h retention time. Nanoporous carbon (NPC) was used as the carrier matrix for the MICCR reactor. SEM and AFM images of NPC used in the MICCR reactor identify different microorganisms on its surface. The microbial profile of NPC used in the MICCR was analyzed, and the relative abundance is phyla Firmicutes, 25.64%; Proteobacteria, 43.68%; Bacteroidetes, 6.58%; Cyanobacteria, 2.22%; Actinobacteria, 2.34% reason for organic removal. The removal of organics follows the pseudo-second-order rate kinetics with the rate constant of 1.75 × 10^-3 L COD^-1 h^-1. For the reactive struvite crystallization, MgO and Na₂HPO₄.2H₂O were taken as the precipitating agents. The optimum molar ratio for the maximum conversion of NH₄⁺-N into struvite was obtained as 1:1.4:1.4 (NH₄⁺-N:MgO:Na₂HPO₄.2H₂O). The volume of struvite precipitate was 48.5 mL/L of TDLWW, and the dry weight was 8.89 g/L. More than 93% of NH₄⁺-N was converted as the struvite fertilizer. The conversion of NH₄⁺-N into struvite follows the pseudo-first-order rate kinetics with the rate constant of 1.67 × 10^-2 min^-1. Despite the conversion of NH₄⁺-N into struvite, COD removal was observed, which confirms the conversion of organic nitrogen into struvite. The struvite was evaluated using SEM, XRD, TGA, DSC, and FT-IR spectroscopic analysis. Hence, the integrated MICCR and the reactive struvite crystallization process can be applied to manage tannery deliming wastewater.

Solvent-assisted cavitation for enhanced removal of organic pollutants - Degradation of 4-aminophenol

A new approach of solvent-assisted cavitation process was proposed for degradation of organic pollutants. The process envisages the use of suitable solvent as an additive, (1-5% v/V), in the conventional cavitation process to enhance the pollutant removal efficiency. A proof of concept was provided for the removal of ammoniacal nitrogen with significantly improved efficiency using solvent-assisted hydrodynamic cavitation (HC) compared to conventional HC. The efficacy of the process was studied on a pilot plant scale (1 m3/h) and using vortex flow based vortex diode as a cavitating device. Degradation studies were carried out using a model pollutant, 4-aminophenol and four different solvents as additives, 1-octanol, cyclohexanol, 1-octane and toluene. Relatively polar solvents were found to increase the efficiency of the pollutant removal (>65%) and also increase the rates to an extent of more than 200%, compared to only HC. A very high removal of ammoniacal nitrogen, more than 90%, was obtained for solvents 1-octanol and cyclohexanol, indicating the importance of the selection of solvent. Per-pass degradation model showed 3 to 4 times increase in the per pass degradation for polar solvents compared to cavitation alone. The results confirm no role of conventional solvent extraction and no specific contamination of wastewater due to the use of solvent as an additive in the process. Further, the cost was 2-3 times lower as compared to the conventional HC. The interesting observations in the proposed process can fuel further research to provide possible improvements in existing methodologies of wastewater treatment, in general, and for removal of ammoniacal nitrogen, in particular.

Remove of ammoniacal nitrogen wastewater by ultrasound/Mg/Al2O3/O3

A large amount of ammoniacal nitrogen wastewater discharged into the water body not only causes eutrophication and black and offensive odor in water, but also increases the difficulty and cost of water treatment, and even produces toxic effects on people and organisms. In this paper, degradation of ammoniacal nitrogen wastewater by the system of ultrasound/Mg/Al₂O₃/ozone (US/Mg/Al₂O₃/O₃) was carried out. The effects of different influencing factors, such as initial pH of the solution, reaction time, temperature, catalyst addition, ozone flow rate, and ultrasonic intensity, on the degradation of ammoniacal nitrogen wastewater were investigated. The optimum reaction conditions were determined. The combination of ultrasonic technology and ozone oxidation technology can enhance the mass transfer of ozone and generate a large amount of HO. Due to Mg/Al₂O₃ catalyst has large surface area, the number of reactive sites and reaction molecule transport channels per unit area increases, resulting in the increase of HO on the surface, thus improving the catalytic activity. The introduction of ultrasound promotes the cleavage of N-H bonds on the catalyst surface, thereby promoting the degradation of ammoniacal nitrogen in the water. Results prove that there is not only a synergistic effect between ultrasound and catalytic ozone oxidation, but a strengthening effect of ultrasound on catalytic ozone oxidation. The research carried out in this paper provides a theoretical basis for the degradation of ammoniacal nitrogen in water.

Evaluation of strategies to enhance ammoniacal nitrogen tolerance by cyanobacteria

In anaerobic digestion of agro-industrial effluents and livestock wastes, concentrations of ammoniacal nitrogen above 800 mg L^-1 are reported to lead to the eutrophication of water bodies. Through the metabolic versatility of microalgae, this nitrogen source can be used and removed, producing carotenoids, phycobiliproteins, polyhydroxyalkanoates, and fatty acids of industrial interest. The challenge of making it feasible is the toxicity of ammoniacal nitrogen to microalgae. Therefore, three strategies were evaluated. The first one was to find species of cyanobacteria with high ammoniacal nitrogen removal efficiency comparing Arthrospira platensis, Synechocystis D202, and Spirulina labyrinthiformis cultivations. The most promising species was cultivated in the second strategy, where cell acclimatization and increasing of the inoculum were evaluated. The cultivation condition that culminated in the best efficiency of ammoniacal nitrogen removal was combined with the third strategy, which consisted of conducting the fed-batch bioprocess. In the batch mode, ammoniacal nitrogen was supplied only once in one fed and was present in high initial concentrations. In fed-batch, multiple feedings with low concentrations of ammoniacal nitrogen were used to decrease the inhibitory effect of ammoniacal nitrogen. Arthrospira platensis showed high potential for ammoniacal nitrogen removal. Using the highest initial cell concentration of Arthrospira platensis cultivated by fed-batch, an increase in the consumption of NH₃ to 165.1 ± 1.8 mg L^-1 and an ammoniacal nitrogen removal efficiency close to 90% were observed. Under this condition, 180.52 ± 11.67 mg g^-1 of phycocyanin was attained. Also, the fed-batch cultivations have the potential to reduce the biomass cost production by 33% in comparison to batch experiments.

Electro-Fenton assisted sonication for removal of ammoniacal nitrogen and organic matter from dye intermediate industrial wastewater

The intricacy in the treatment of effluents from the textile sector attracts the researchers since 20th century. Dye intermediate manufacturing industries are responsible for producing the toxic pollutants such as nitro-aromatics, benzene, toluene, phenol, heavy metals etc. with intense colour. The present study focuses on the performance of combined Electro-Fenton (EF) and sonication for the removal of ammoniacal nitrogen and COD from dye intermediate manufacturing wastewater. Batch experiments of EF were performed using graphite electrodes and sonication was applied to the EF treated wastewater to enhance the treatment performance. A number of experiments were executed to discover the influence of pH, applied voltage, Fenton catalyst dosage and time of electrolysis on the removal efficiency of EF batch process was scrutinized. The pH was varied between 2 and 4, applied voltage from 1 to 4V, Fenton catalyst dosage between 50 and 200 mg L^-1 and time between 15 and 180 min. At optimum condition i.e. pH 3, applied voltage 3V, Fenton catalyst dosage of 100 mg L^-1and 120 min electrolysis time, the percentage removal obtained for ammoniacal nitrogen and COD were 59.4% and 79.2% respectively. The removal efficiency was increased to 65.5% for ammoniacal nitrogen and 85.4% for COD after applying sonication to the EF treated wastewater. The removal of ammoniacal nitrogen and COD can be achieved in a scientific and feasible way by combining EF process with sonication.

Evaluation of wastewater treatment performance to a field-scale constructed wetland system at clogged condition: A case study of ammonia manufacturing plant

Assessment of the treatment performance in the field-scale hybrid constructed wetland (CW) for ammonia manufacturing plant remains limited. After being in operations running on and off since 2014, the hybrid CW which treats effluent from the ammonia manufacturing plant in Peninsular, Malaysia has recently demonstrated the full clogging to the CW. It takes only 8 months to demonstrate a big deterioration of performance in 2019. Though the mechanism of clogging is not clear, which can be partially from inherent design problems or operational issues, nonetheless, it is important to evaluate how this clogging has impacted the effluent treatment performance and the continuous utilization of the CW. The purpose of this study is to evaluate the impact of the treatment performance on the ammoniacal nitrogen and COD removal when the CW is clogged. The result revealed that there is no impact on COD removal, but it has a substantial impact on the ammoniacal nitrogen removal. The ammoniacal nitrogen removal dropped to negative (outlet concentration is higher than inlet concentration) during the clogged period. Another observation is, the low removal rate also coincides with a high COD/N ratio, when the COD/N ratio increased to >2, the ammoniacal nitrogen removal rate dropped substantially, with the coefficient of determination, R² of 40.5%. The root cause for the clogging to develop in a short period of time is unidentified. However, it is still worth noting that COD and ammoniacal nitrogen efficiency did not behave the same at the clogged CW.

Effect of Ca:Mg ratio and high ammoniacal nitrogen on characteristics of struvite precipitated from waste activated sludge digester effluent

This study revealed the relationship between the presence of calcium impurities and ammoniacal nitrogen concentration upon crystallization of struvite. The research hypothesis was that the presence of both calcium and high concentrations of ammoniacal nitrogen (328-1000 mg/L) in waste activated sludge may influence the struvite quality and acid stability. Hence, we studied the impact of Ca:Mg ratio upon morphology, particle size, purity and dissolution of struvite, in the presence of varying levels of excess ammoniacal nitrogen. X-ray diffraction revealed that up to 31.4% amorphous material was made which was assigned to hydroxyapatite. Increasing the ammoniacal nitrogen concentration and elevation of the Mg:Ca ratio maximized the presence of struvite. Struvite particle size was also increased by ammoniacal nitrogen as was twinning of the crystals. Tests with dilute solutions of organic acid revealed the sensitivity of struvite dissolution to the physical characteristics of the struvite. Smaller particles (21.2 μm) dissolved at higher rates than larger particles (35.86 μm). However, struvite dissolved rapidly as the pH was further reduced irrespective of the physical characteristics. Therefore, addition of struvite to low pH soils was not viewed as beneficial in terms of controlled nutrient release. Overall, this study revealed that waste activated sludge effluent with high ammoniacal nitrogen was prospective for synthesis of high quality struvite material.

Ruminal and histological characteristics and nitrogen balance in lamb fed diets containing cactus as the only roughage

This study examined rumen fermentation, histological, blood, and urinary characteristics as well as ammoniacal nitrogen concentration, pH, nitrogen balance, and microbial protein in lamb fed diets containing spineless cactus as the sole roughage source plus levels of wheat bran (WB) in comparison with a control diet based on spineless cactus and buffelgrass. Twenty-eight uncastrated, crossbreed lambs with an average initial weight of 22.6 ± 2.37 kg were used in the experiment. The treatments consisted of a standard diet (control) containing buffelgrass and spineless cactus and three diets containing cactus as the only roughage source plus varied concentrations of WB (30, 37, and 44%, on a dry matter basis). Results were evaluated by analysis of variance, and contrasts were applied at the 5% probability level for mean comparison. Rumen villus height and width were greater and musculature was lower in the lamb fed diets containing 37% and 44% WB compared with those fed control diet. In the intestine, the crypts were smaller in the animals which consumed the diets with 30, 44, and 37% WB. All WB levels resulted in lower nitrogen intake and retention. Microbial protein concentration, microbial protein efficiency, microbial nitrogen, urea, and glucose were not significantly affected. Feeding lamb with diets containing levels of wheat bran, with cactus as the only roughage source, does not negatively affect their ruminal-fermentation, blood, and urinary characteristics; ammoniacal nitrogen concentration; pH; or microbial protein. However, nitrogen balance and ruminal and intestinal morphometric characteristics are impaired.

Microeukaryote community in a partial nitritation reactor prior to anammox and an insight into the potential of ciliates as performance bioindicators

An in-depth, long-term, multidisciplinary study was conducted in order to study the microeukaryote community in a partial nitritation (PN) reactor prior to anammox. The PN reactor operated with moving bed biofilm reactor (MBBR) technology, using plastic supports (carriers) for biofilm development. The microeukaryote community from the biofilm (BF) and the surrounding media (mixed liquor or ML) were analysed separately. Despite the physicochemical conditions under which the PN-MBBR operated (an average of 305.9±117mg TAN l^-1 and 328.4±131.9mg N-NO₂^- l^-1), up to 24 microeukaryotic taxa were observed by microscope. Microeukaryote species showed an uneven distribution in the PN-MBBR, thus suggesting the existence of two habitats: the BF, preferred by species with specific structures for adhering to a substrate, such as the stalked Peritrichia, and the ML, preferred by free-swimming or non-substrate dependent species. The results indicated that most ciliate population dynamics mainly responded to the nitrous acid and free ammonia concentrations and, to a lesser extent, to sCOD values. In the BF, variations in the population of Epistylis camprubii and Opercularia coarctata suggest the existence of competition between these species due to niche overlap. A V4 18S rDNA molecular survey (Illumina) was carried out for some samples with the aim of obtaining maximum coverage of the main eukaryote species that were microscopically detected throughout the study. The diversity and abundance data provided by both detection methods were compared. The study helped identify broader tolerance ranges of the microeukaryote taxa to the physicochemical parameters analysed.

Rural environment study for water from different sources in cluster of villages in Mehsana district of Gujarat

Water pollution and water scarcity are major environmental issues in rural and urban areas. They lead to decline in the quality of water, especially drinking water. Proper qualitative assessment of water is thus necessary to ensure that the water consumed is potable. This study aims to analyze the physicochemical parameters in different sources of water in rural areas and assess the quality of water through a classification system based on BIS and CPCB standards. The classification method has defined water quality in six categories, viz., A, B, C, D, E, and F depending on the levels of physicochemical parameters in the water samples. The proposed classification system was applied to nine villages in Kadi Taluka, Mehsana district of Gujarat. The water samples were collected from borewells, lakes, Narmada Canal, and sewerage systems and were analyzed as per APHA and IS methods. It was observed that most of the physicochemical parameters of Narmada Canal and borewell water fell under class A, thus making them most suitable for drinking. Further, a health camp conducted at Karannagar village, Mehsana revealed no incidents of any waterborne diseases. However, there were certain incidents of kidney stones and joint pain in few villages due to high levels of TDS. Toxic metal analysis in all the water sources revealed low to undetectable concentration of toxic metals such as lead, arsenic, mercury, and cadmium in all the water sources. It is also recommended that the regular treatment of the Narmada Canal water be continued to maintain its excellent quality.

Treatment of landfill leachate using ASBR combined with zeolite adsorption technology

Sanitary landfilling is the most common way to dispose solid urban waste; however, improper landfill management may pose serious environmental threats through discharge of high strength polluted wastewater also known as leachate. The treatment of landfill leachate to fully reduce the negative impact on the environment, is nowadays a challenge. In this study, an aerobic sequencing batch reactor (ASBR) was proposed for the treatment of locally obtained real landfill leachate with initial ammoniacal nitrogen and chemical oxygen demand (COD) concentration of 1800 and 3200 mg/L, respectively. ASBR could remove 65 % of ammoniacal nitrogen and 30 % of COD during seven days of treatment time. Thereafter, an effective adsorbent, i.e., zeolite was used as a secondary treatment step for polishing the ammoniacal nitrogen and COD content that is present in leachate. The results obtained are promising where the adsorption of leachate by zeolite further enhanced the removal of ammoniacal nitrogen and COD up to 96 and 43 %, respectively. Furthermore, this combined biological-physical treatment system was able to remove heavy metals, i.e. aluminium, vanadium, chromium, magnesium, cuprum and plumbum significantly. These results demonstrate that combined ASBR and zeolite adsorption is a feasible technique for the treatment of landfill leachate, even considering this effluent's high resistance to treatment.