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The presence of ammonium (NH4+) in wastewater above the permissible limits leads to undesirable ecological impact and public health concerns. In this study, the anaerobic ammonium oxidizing (anammox) bacteria-mediated nitrogen removal was investigated using a sequential batch reactor (SBR). Effects of different salinity levels were evaluated on the bacterial activity at: mild (below 0.2 g NaCl/L), elevated (18.2 g NaCl/L) and suitable salinity (2–0.5 g NaCl/L) levels mimicking the environmental conditions that are present in real wastewater. Within a suitable salinity period of 0.5–2 g NaCl/L, the highest average total nitrogen removal efficiencies (TNREs) and total nitrogen removal rates (TNRRs) of 67 (± 11)% and 37 (± 29) g N/m3/d, respectively, were achieved. In addition to the salinity tests, the effect of relatively high nitrite levels (> 40 mg N/L) was observed in the reactor resulting in the decrease in anammox activity, but increasing biomass potential for the treatment of high nitrite containing wastewater. Interestingly, the supplementation of hydrazine at 7.5 mg N2H4/L indicated enhanced anammox activity with a nitrogen removal rate of 0.7 ± 0.01 mg N/g MLSS/h, while test without hydrazine showed a rate of 0.68 ± 0.06 mg N/g MLSS/h. Therefore, denitrifying activity decreased with the addition of hydrazine, which on the other hand benefits the anammox start-up. Illumina sequencing analysis revealed that the microbial community has changed with the rise of the salinity levels and was dominated with Anaerolineae, Gammaproteobacteria, Clostridia and various key anammox organisms, such as Candidatus Brocadia and Candidatus Kuenenia strains (at 3%). [ABSTRACT FROM AUTHOR]

The study presents the research results on the rejected water generated in dewatering sludge stabilised in Autothermal Thermophilic Aerobic Digestion (ATAD) technology. The research was carried out in three municipal wastewater treatment plants (WWTPs), with a capacity of 1500 to 3260 m3 d−1 and a sludge node capacity of 835 to 2000 kg DM d−1. The mean content of Kjeldahl nitrogen (TKN) in the rejected water samples taken from each object ranged from 485 to 1573 mg N L−1, ammonium nitrogen 318 to 736 mg N L−1, and the average concentration of total phosphorus ranged from 96 to 281 mg P L−1. The average content of organic matter expressed as five-day biological oxygen demand (BOD5) ranged from 205 to 730 mg O2 L−1, while chemical oxygen demand (COD) ranged from 767 to 4884 mg O2 L−1. The study determined the kinetics of the biochemical decomposition of organic matter, assuming that it follows the first-order equation. The average reaction rate constant k in subsequent treatment plants was estimated at 0.424, 0.513 and 0.782 d−1. The R2 coefficient determining the model's adjustment to empirical values was not lower than 0.952. The organic matter biodegradability index average values ranged from 0.17 to 0.26. [ABSTRACT FROM AUTHOR]

The study presents the research results on the rejected water generated in dewatering sludge stabilised in Autothermal Thermophilic Aerobic Digestion (ATAD) technology. The research was carried out in three municipal wastewater treatment plants (WWTPs), with a capacity of 1500 to 3260 m3 d−1 and a sludge node capacity of 835 to 2000 kg DM d−1. The mean content of Kjeldahl nitrogen (TKN) in the rejected water samples taken from each object ranged from 485 to 1573 mg N L−1, ammonium nitrogen 318 to 736 mg N L−1, and the average concentration of total phosphorus ranged from 96 to 281 mg P L−1. The average content of organic matter expressed as five-day biological oxygen demand (BOD5) ranged from 205 to 730 mg O2 L−1, while chemical oxygen demand (COD) ranged from 767 to 4884 mg O2 L−1. The study determined the kinetics of the biochemical decomposition of organic matter, assuming that it follows the first-order equation. The average reaction rate constant k in subsequent treatment plants was estimated at 0.424, 0.513 and 0.782 d−1. The R2 coefficient determining the model’s adjustment to empirical values was not lower than 0.952. The organic matter biodegradability index average values ranged from 0.17 to 0.26.

In this study, a bio-electrochemical reactor comprising of anaerobic and aerobic chambers with filled granular activated carbon as biocarrier and third electrode was developed to investigate the effect of ammonium and COD concentrations on the power generation and COD removal. Two important operating parameters including initial COD concentrations (50–2000 mg/L) and initial ammonium concentrations (40–1000 mg/L) were optimized to attain the best response of electricity generation and COD removal using response surface methodology (RSM) through an experiments design software. A total of thirteen runs of experiments were employed for statistical analysis of data and developing empirical model, which has ability to predict optimum condition. Based on the results, the maximum COD removal efficiency was 96.8%, when the produced current at the maximum level was 1.149 mA. It was found that main variables as solely or combination effects significantly affect the efficiency of MFCs. Image 1 • To develop a novel fixed bed air-cathode microbial fuel cells. • To conduct simultaneous nitrification and denitrification and carbon removal. • To investigate the effects of NH 4 +-N, and COD concentrations on the MFC performance. • To develop mathematical models using RSM. • To optimize the variables and responses. [ABSTRACT FROM AUTHOR]

Fluoride removal from aqueous solutions was studied using nanofiltration and sorption techniques which have always been best key ways to deal with water contaminated by fluoride. In this presented work, we were firstly interested on fluoridated rejected water overcoming the drawback of RO membrane process of groundwater treatment plant in Baltic region (Kretinga, Lithuania). Opoka sorbent has shown effective results of fluoride sorption with efficiency higher than 77 %. In order to understand the sorption phenomenon and to validate the results obtained, we have applied experimental data on Freundlich and Langmuir isotherms which allow us to determine isotherms parameters (KF; 1/n and KL; qmax) and to confirm the experiment. Because of the unacceptable tariff of drinking water treated by RO, defluoridation with nanofiltration method is proposed in this study as a solution which can replace reverse osmosis technique. For that, tests of nanofiltration for fluoride removal were carried out at laboratory scale by using nanofiltration flat sheet membranes (NF270 and NF90). [ABSTRACT FROM AUTHOR]

Wastewater treatment plants (WWTPs) are important routes for releasing microplastics into the environment, with the produced sludge acting as a recipient of microplastics from wastewater. There is little information on the impact of sludge processes on the number of microplastics in sludge. In this study, the presence of microplastics in sludge produced by the Sari WWTP in northern Iran was investigated. Samples were taken in 3 replications and microplastics larger than 37 μm were extracted. The sludge from primary settling tank, clarifier, after sludge thickener and after aerobic digester, and after dewatering contained 214, 206, 200, 238, and 129 microplastics/g dry weight, respectively. According to the amount of sludge produced for each unit, this equals 280, 362, 599, 601, and 276 million microplastics/day, respectively, of which more than 85% were fibers. The numbers of microplastics in the sludge from the output of the sludge thickener and the aerobic digester did not significantly differ. However, their numbers decreased by more than 50% after dewatering, probably due to the destruction of flocs in the digestive process and the release of attached microplastics, which are returned into the wastewater treatment process with the rejected water. Polyester and polyethylene were the predominant types of fibers and particles, respectively. Given the annual amount of sludge produced, more than 100 billion microplastics enter the environment per year. Wastewater sludge, therefore, is an important source for the emission of microplastics, especially fibers, to the environment, warranting further evaluation of the associated environmental hazards. [Display omitted] • Primary and secondary sludge contribute most to the separation of MPs from wastewater. • Fibers are the predominant type of MPs in wastewater sludge. • Dewatering reduced the numbers of MPs in sludge by more than 50%. • Large amounts of MPs are returned to the aeration tank by rejected water. [ABSTRACT FROM AUTHOR]