Energy-Positive Disintegration of Waste Activated Sludge—Full Scale Study

This study aimed to evaluate the effects of mechanical disintegration of waste activated sludge (WAS) on full scale anaerobic digestion, considering the possibility of obtaining a positive energy balance. The results showed that an increase in energy density (εL) used in disintegration was accompanied by an increase in the release of organic compounds from sludge (SCOD increased from 211 ± 125 mg O2/L for εL = 0 kJ/L to 6292 ± 2860 mgO2/L for εL = 180 kJ/L). Some of them were volatile fatty acids. The percentage share of WAS subject to disintegration was also documented as a crucial parameter affecting the efficiency of biogas production. An increase in the value of this parameter from 25% to 100%, even at much lower εL used in disintegration (therefore with much smaller amounts of organic compounds released from sludge flocs) resulted in an increase in biogas production. Conducting disintegration of the entire stream of WAS directed to the fermentation tank at εL 30 kJ/L resulted in an increase in biogas production by 14.1%. Such a surplus would allow production of approximately 360 kWh/d net electricity. Mechanical disintegration of thickened WAS therefore may be an economically justifiable strategy for the intensification of anaerobic sludge stabilisation.

Efficiency of an up-flow Anaerobic Sludge Blanket reactor coupled with an electrochemical system to remove chloramphenicol in swine wastewater

The application and design of treatment systems in wastewater are necessary due to antibiotics' potential toxicity and resistant genes on residual effluent. This work evaluated a coupled bio-electrochemical system to reduce chloramphenicol (CAP) and chemical oxygen demand (COD) on swine wastewater (SWW). SWW characterization found CAP of <10 μg/L and 17,434 mg/L of COD. The coupled system consisted of preliminary use of an Up-flow Anaerobic Sludge Blanket Reactor (UASB) followed by electrooxidation (EO). UASB reactor (primary stage) was operated for three months at an organic load of 8.76 kg of COD/m3d and 50 mg CAP/L as initial concentration. In EO, we carried out a 22 (time operation and intensity) factorial design with a central composite design; we tried two Ti cathodes and one anode of Ti/PbO2. Optimal conditions obtained in the EO process were 240 min of operation time and 1.51 A of current intensity. It was possible to eliminate 44% of COD and 64.2% of CAP in the preliminary stage. On bio-electrochemical, a total COD and CAP removal were 82.35% and >99.99%, respectively. This coupled system can be applied to eliminate antibiotics and other organic pollutants in agricultural, industrial, municipal, and other wastewaters.

Enrichment of Homoacetogens Converting H2/CO2 into Acids and Ethanol and Simultaneous Methane Production

An anaerobic granular sludge was enriched to utilize H2/CO2 in a continuous gas-fed up-flow anaerobic sludge reactor by applying operating conditions expected to produce acetic acid, butyric acid and ethanol. Three stages of fermentation were found: Stage I with acetic acid accumulation with the highest concentration of 35 mM along with a pH decrease from initial 6 to 4.5. In Stage II, H2/CO2 was replaced by 100% H2 to induce solventogenesis, whereas butyric acid was produced with the highest concentration of 2.5 mM. At Stage III with 10 μM tungsten (W) addition, iso-valeric acid, valeric acid and caproic acid were produced at pH 4.5 -5.0. In the batch tests inoculated with the enriched sludge taken from the bioreactor (day 70), however, methane production occurred at pH 6. Exogenous 15 mM acetate addition enhanced both the H2 and CO2 consumption rate compared to exogenous 10, 30 and 45 mM acetate by the enriched sludge. Exogenous acetate failed to be converted to ethanol using H2 as electron donor by the enriched acetogens.

MICROBIAL ENRICHMENT PROCESS IN THE ANODE OF MICROBIAL FUEL CELL SYSTEM USING TOFU WASTEWATER (TWW) ANAEROBIC SLUDGE

Microbial fuel cell consisting two main components which are anode and cathode materials. In the microbial fuel cell, both anode and cathode compartments are separated with a separator. Anode generates the protons and electrons while cathode converts protons into water with the presence electrons and oxygen. During the Microbial fuel cell operation, the performance of anode is very crucial due to it provides the protons and electrons. Hence, the high efficiency microbial fuel cell is very related with the high anode performance. This work addressed to the enrichment process of electroactive bacteria (EAB) in anode of microbial fuel cell. In this work, some parameters such as current generations, , and pH changes were used to assess the enrichment process of EAB was reached. In addition, the presence of EAB on the anode surface was identified based on the morphology of anode surface. The removal of COD and the pH value were determined by using the American public health analysis method and pH tester, respectively. The morphology of anode surface was analysed by using a scanning electron microscope. Whereas, current generation was tested by using a mustimeter. The removal of COD and final pH were obtained 71.4 % and 5.7, respectively. The optimum current generation was observed 0.19 mA. The surface morphology of anode before enriched with microbes was clear surface, while after enriched with microbes was attached by microbes. The removal of COD, pH changes, current generation and morphology of anode surface could be used to assess the EAB in the anode compartment. Keywords: Microbial fuel cell; anode; cathode; electroactive bacteria; pH changes.

PROJETO DE REATOR ANAERÓBIO DE FLUXO ASCENDENTE (RAFA) PARA TRATAMENTO DE VINHAÇA

Brazil is the largest sugar and alcohol producer in the world, consequently, it is also a major vinasse producer, which is a problem, as it has a high potential for pollution, severely impacting the soil and water, despite being used in fertigation of cane fields. When treated in anaerobic conditions, however, it can produce energy and be used as a biofertilizer for the soil. This treatment can be performed by an Upflow Anaerobic Sludge Blanket (UASB), considered efficient by the literature. Based on this, this article tries to gather equations and collect data, reviewing the scientific literature with the objective of designing an UASB for the treatment of vinasse, exposing an alternative of suitable final disposal for this by-product. The results show good opportunities, with a great potential for reducing BOD and COD and producing biogas, electricity and biofertilizer, in addition to providing a compilation of equations and important data for future calculations.

Anaerobic Digestion for Biogas Production from Municipal Sewage Sludge: A Comparative Study between Fine Mesh Sieved Primary Sludge and Sedimented Primary Sludge

Two different types of primary sewage sludge have been used as feedstock for production of biogas through anaerobic digestion (AD): the one type was sludge from a typical primary clarifier (PC), while the other type of sludge produced by a rotating belt filter, commonly called microsieve (MS). Initially the main physicochemical characteristics of the sludges, such as total solids (TS), volatile solids (VS), VS/TS, pH and carbon to nitrogen ratio (C/N) were determined, for MS: 37.86 ± 0.08%, 83.00 ± 0.41%, 0.83 ± 0.00, 6.67 ± 0.08 and 19.68 ± 0.69, respectively, and for PC: 2.61 ± 0.08%, 78.77 ± 1.91%, 0.79 ± 0.02, 6.61 ± 0.10 and 14.46 ± 1.23, respectively. Then, calculated amounts of the sludges were inserted into airtight vials and were inoculated using anaerobic sludge. The daily biogas production was measured over a period of 30 days. PC sludge maximized the daily biogas production (44.20 mlbiogas/gvsd) 11 days after inoculation, while the MS sludge reach a peak (37.74 mlbiogas/gvsd) 14 days after inoculation. The cumulative biogas production over the 30 days of AD was in the same laver (442.29 mlbiogas/gvs for PC versus 434.73 mlbiogas/gvs for MS). However, PC sludge indicated higher daily biogas production, compared to MS sludge, while the opposite was observed for the period following the peak point. The Volatile Solids Reduction for PC and MS sludges was recorded as 46.06% and 32.39%, respectively.

Nitrogen Removal by an Anaerobic Iron-Dependent Ammonium Oxidation (Feammox) Enrichment: Potential for Wastewater Treatment

Nitrogen pollution in water is a growing concern. Anthropogenic activities have increased the amount of nitrogen released into watercourses, which harms human health and the environment, and causes serious problems, such as eutrophication. Feammox is a recently discovered biological pathway associated with the nitrogen cycle that has gained scientific interest. This process couples anaerobic ammonium oxidation with iron reduction. This work presents a study on the Feammox mechanism from the enrichment of an activated sludge obtained from a sewage treatment plant. The enrichment was carried out at neutral pH to study the N2 pathway, that is, the Feammox process with the oxidation of ammonium (NH4+) directly to N2. In addition, different sources of iron were studied: iron chloride (FeCl3); ferrihydrite; and goethite. The characterization of the sludge showed the genes associated with ammonia monooxygenase, nitrate and nitrite reductases processes, along with relevant microbial species. The enrichment, carried out for 42 days and monitored every 14 days, showed that FeCl3 as a source of Fe was more effective for the coupled process of oxidation of NH4+ and the reduction of Fe(III) to Fe(II). At the end of the enrichment period, a removal of 31% and 32.2% of NH4+, and an increase in Fe(II) concentration by 52.4 and 63.9 times regarding the initial value were achieved in aerobic and anaerobic sludge, respectively. This study provides information on the potential of Feammox in the removal of N from wastewater, and the oxidation/reduction yields in the initial enrichment phase.