Arsenic thiolation and the role of sulfate-reducing bacteria from the human intestinal tract

BACKGROUND: Arsenic (As) toxicity is primarily based on its chemical speciation. Although inorganic and methylated As species are well characterized in terms of metabolism and formation in the human body, the origin of thiolated methylarsenicals is still unclear. OBJECTIVES: We sought to determine whether sulfate--reducing bacteria (SRB) from the human gut are actively involved in the thiolation of monomethylarsonic acid (MMA(V)). METHODS: We incubated human fecal and colon microbiota in a batch incubator and in a dynamic gut simulator with a dose of 0.5 mg MMA(V) in the absence or presence of sodium molybdate, an SRB inhibitor. We monitored the conversion of MMAV into monomethyl monothioarsonate (MMMTA(V)) and other As species by high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry analysis. We monitored the sulfate-reducing activity of the SRB by measuring hydrogen sulfide (H2S) production. We used molecular analysis to determine the dominant species of SRB responsible for As thiolation. RESULTS: In the absence of sodium molybdate, the SRB activity-primarily derived from Desulfovibrio desulfuricans (piger)-was specifically and proportionally correlated (p < 0.01) to MMA(V) conversion into MMMTA(V). Inactivating the SRB with molybdate did not result in MMA(V) thiolation; however, we observed that the microbiota from a dynamic gut simulator were capable of demethylating 4% of the incubated MMA(V) into arsenous acid (iAs(III)), the trivalent and more toxic form of arsenic acid (iAs(V)). CONCLUSION: We found that SRB of human gastrointestinal origin, through their ability to produce H2S, were necessary and sufficient to induce As thiolation. The toxicological consequences of this microbial As speciation change are not yet clear. However, given the efficient epithelial absorption of thiolated methylarsenicals, we conclude that the gut microbiome-and SRB activity in particular-should be incorporated into toxicokinetic analysis carried out after As exposure

Use of calcium/iron oxide composites for sorption of phosphorus from wastewater

Received: January 31st, 2023 ; Accepted: May 28th, 2023 ; Published: June 27th, 2023 ; Correspondence: [email protected] development of an effective, low-cost and natural sorbent is of great significance for phosphorus removal and recovery from small and medium size industrial and municipal wastewater. Commonly used phosphorus removal methods are costly and thus rarely applied in the small-scale WWTPs. This research was aimed at preparing and characterising three different calcium/iron composites for evaluating their sorption performance for the removal of phosphorus from aqueous solutions and domestic wastewater. The obtained composite materials belonging to the Brownmillerite mineralogical subgroup were characterised by the Powder X-ray Diffraction (PXRD), specific surface area analysis by Brunauer-Emmett-Teller (BET) method and scanning electron microscope (SEM). It was found that for aqueous solutions the sorption process is pH- dependent, showing the optimal sorption conditions for phosphorus removal at pH 3 to pH 6. However, all three proposed composites significantly increased the pH of wastewater. All three tested materials adsorbed phosphorus from wastewater. Maximal phosphorus adsorption capacity from the domestic wastewater was 17.75 mg g-1 , 8.25 mg g-1 and 4.46 mg g-1 for CaFeOxide, CaFeHydr and CaFeReg respectively. In further research it is planned to develop an environmentally friendly and cost-effective phosphorus recovery technology with the potential to apply the used sorbent as a slow-release fertiliser in agriculture

SMOOTH TEMPERATURE DECREASING FOR NITROGEN REMOVAL IN COLD (9-15° C) ANAMMOX BIOFILM REACTOR TESTS

For N-rich wastewater treatment the anaerobic ammonium oxidation (anammox) and nitritation-anammox (deammonification) processes are widely used. In a deammonification moving bed biofilm reactor (MBBR) a maximum total nitrogen removal rate (TNRR) of 1.5 g N m-2d-1(0.6 kg N m-3d-1) was achieved. During biofilm cultivation, temperature was gradually lowered by 0.5° C per week, and a similar TNRR was sustained at 15° C. qPCR analysis showed an increase in Candidatus Brocadia quantities from 5×103 to 1×107 anammox gene copies g-1 TSS despite temperature lowered to 15° C. Fluctuations in TNRR were rather related to changes in influent NH4+ concentration. To study the short-term effect of temperature on the TNRR, a series of batch-scale experiments were performed which showed sufficient TNRRs even at 9-15° C (4.3-5.4 mg N L-1 h-1, respectively) with anammox temperature constants ranging 1.3-1.6. After biomass was adapted to 15° C, the decrease in TNRR in batch tests at 9° C was lower (15-20%) than for biomass adapted to 17-18° C. Our experiments show that a biofilm of a deammonification reactor adapted to 15° C successfully tolerates shortterm cold shocks down to 9° C retaining a high TNRR

Stability of the Broiler Antibody Under Heat Stress Using Dry Rice

This study examines the impact of using dry rice, characterized by low calories and high resistant starch content, on broiler performance under heat stress conditions in Indonesia. Broilers face challenges related to stress, particularly heat stress, which can compromise their immunity. The research investigates the potential of resistant starch in dry rice to enhance broiler digestion performance and immunity. The experiment, conducted at Zakiyah Farm and the Laboratory of the Wates Veterinary Center, Yogyakarta, involved three treatments (T1, T2, and T3) with five replications each. Observed variables included water consumption, carcass weight, Packed Cell Volume (PCV), bursa fabricius weight, and Hi-Test Nd antibody levels. Results showed no significant impact on water consumption, carcass weight, and PCV across all treatments. However, a decrease in bursa weight in T1 and T3 indicated an increased level of stress. The lowest seropositive Hi-Test Nd values in T1 and T3 suggested that the use of dry rice through the sowing method might alleviate heat stress on broilers. In conclusion, this research emphasizes the potential of dry rice to maintain the stability of broiler antibodies under heat stress conditions, emphasizing the need for further exploration of alternative dietary components

Techno-economic Analysis of Rooftop Photovoltaic System (RPVS) using Thin-Frameless Solar Panels for Household Customers in Indonesia

The availability of thin-frameless solar panels on the market today makes the installation of rooftop Photovoltaic (RPVS) systems more attractive. The purpose of this research is to analyze financially the use of thinframeless solar panels for on-grid RPVS by household electricity customers in Indonesia. The investment cost, the maintenance costs, and the electricity cost savings were involved for the financial analysis, such as Internal Rate of Return (IRR), Net Present Value (NPV), and Pay Back Period (PBP). The calculation is carried out for ideal conditions, the direction of a non-ideal rooftop and the yearly increase of electricity prices is 15 %. The analysis results show that the minimum available rooftop area is still sufficient for the rooftop area needs for solar panel placement, the thin solar panels are safer than standard solar panels, and savings on electricity payments for the return on investment of the RPVS is to be attractive with the IRR > 12 %. The average investment cost of the non-ideal condition is 8 % higher than the ideal condition. This study provides an overview to the policymakers and developers in exploiting the potential of RPVS, especially in Indonesia. For future research directions, this study needs to analyze the technical and economic feasibility of using hybrid smart-grid technology with batteries

Anaeroobset ammoniumi oksüdatsiooniprotsessi läbiviivate bakterite rikastamine anaeroobse kääriti väljavoolu lämmastikurikka vädu käitlemiseks ning anammox protsessi kiirendamine protsessi vaheühenditega

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Lämmastikurikaste reovete käitlemine tavapäraste nitrifikatsiooni-denitrifikatsiooni meetoditega on energiamahukas. Antud doktoritöös uuriti alternatiivset viisi lämmastikuärastuse läbiviimiseks autotroofsete bakterikultuuride abil. Dissertatsiooni raames rikastati anaeroobset ammooniumi oksüdatsiooni (anammox) protsessi läbiviivaid baktereid setteveest biokilekandjatele ning lämmastikuärastust teostati liikuvate biokilekandjatega süsteemis. Erinevates biokilesüsteemides (maksimaalne lämmastikuärastuse kiirus 1 kg N m–3 d–1) käivitati efektiivne kahe-etapiline ning üheetapiline autotroofne lämmastikuärastuse protsess anaeroobse kääriti separeerimisel allesjääva lämmastikurikka vädu käitlemiseks. Dissertatsioonis hinnati ka anammox protsessi vaheühendite mõju nitriti poolt inhibeeritud ja inhibeerimata anammox protsessil põhineva biokilesüsteemi kandjate lämmastikuärastuse efektiivsusele. Antud vaheühendite lisamine võimaldab ületada nitriti poolt pärsitud anammox-süsteemides inhibitsiooni, samal ajal kiirendades lämmastikuärastust. Pärast kaheetapilise (nitritatsioon ja anammox protsessid eraldi mahutites) anammox protsessi käivitamist liikuvate biokilekandjatega süsteemis saavutati üheetapilistes lämmastikuärastuse süsteemides efektiivne nitritatsiooni ning deammonifikatsiooni protsess kõrgendatud vaba ammoniaagi (FA) ning kõrgendatud HCO3– (CO2) kontsentratsiooni tingimustes. Antud meetoditel käivitatud autotroofne lämmastikuärastuse protsess on võimalik senisest energiaefektiivsemal moel tööle seada ka täismahulistel reoveepuhastuse seadmetel lämmastikurikaste reovete käitlemiseks.Autotrophic nitrogen removal technologies have been developed to save energy on aeration and on addition of organic carbon sources. In this study the technology of anaerobic ammonium oxidizing (anammox) bacteria enrichment and the performance of a moving bed biofilm reactor for the treatment of nitrogen-rich wastewater was studied in detail. Reject water the anaerobic digester effluent of the Tallinn Wastewater Treatment Plant was used as a substrate and also as a source of anammox bacteria. The anammox organisms were enriched onto the biofilm carriers’ by selective environmental conditions and substrate loading. Satisfactory autotrophic total nitrogen (TN) removal rates (1 kg N m–3 d–1) were achieved for the treatment of digester effluent showing a potential for a full-scale application of the developed technology. The anammox process started up with carriers having nitrifying biomass on it showed a somewhat better stability against increased nitrite concentrations. Rapid overcoming from nitrite inhibition or tolerance to higher nitrite concentrations is important for sustaining a stable TN removal rate in anammox process operated at high substrate loading. We have demonstrated the acceleration of post-inhibition recovery of the anammox process by optimum (small) amounts of intermediate metabolites (hydrazine and hydroxylamine) on the anammox process, which is a matter of great interest as it can be used in case of inhibition in water treatment systems. After the start-up of two-stage deammonification systems, the nitritation process was developed from the nitrifying process by limiting the activity of nitrite oxidizing bacteria to minimum. A suitable technique for that was application of a combination of low HRT, increased free ammonia and inter¬mittent aeration. The deammonification process in a single reactor encountered problems when nitrite was further oxidized into nitrate in a form mainly unavailable to anammox organisms. Nitrite oxidation into nitrate was avoided by means of applying increased free ammonia (FA) concentration and also by increased HCO3– (CO2) concentrations. The methods developed for the start-up of one and two-step deammonification processes and for anammox bacteria enrichment and inhibition recovery can be applied for a full-scale cost-saving treatment