Joanna Rodziewicz

Effect of the C:N:P ratio on the denitrifying dephosphatation in a sequencing batch biofilm reactor (SBBR)

A series of investigations were conducted using sequencing batch biofilm reactor (SBBR) to explore the influence of C:N:P ratio on biological dephosphatation including the denitrifying dephosphatation and the denitrification process. Biomass in the reactor occurred mainly in the form of a biofilm attached to completely submerged disks. Acetic acid was used as the source of organic carbon. C:N:P ratios have had a significant effect on the profiles of phosphate release and phosphate uptake and nitrogen removal. The highest rates of phosphate release and phosphate uptake were recorded at the C:N:P ratio of 140:70:7. The C:N ratio of 2.5:1 ensured complete denitrification. The highest rate of denitrification was achieved at the C:N:P ratio of 140:35:7. The increase of nitrogen load caused an increase in phosphates removal until a ratio C:N:P of 140:140:7. Bacteria of the biofilm exposed to alternate conditions of mixing and aeration exhibited enhanced intracellular accumulation of polyphosphates. Also, the structure of the biofilm encouraged anaerobic-aerobic as well as anoxic-anaerobic and absolutely anaerobic conditions in a SBBR. These heterogeneous conditions in the presence of nitrates may be a significant factor determining the promotion of denitrifying polyphosphate accumulating organism (DNPAO) development.

Electrolytically aided denitrification on a rotating biological contactor

The study was conducted at a bench scale on a rotating biological contactor under both conventional conditions (without the flow of electric current) and with the passage of an electric current having the following densities: 0.2 A m−2, 0.8 A m−2 and 1.5 A m−2. Stainless‐steel discs covered with an immobilized biofilm served as a cathode, whereas an electrode made of stainless steel immersed in the wastewater of the flow tank of the contactor served as an anode. Experiments were carried out on municipal wastewater containing nitrogen in the organic and ammonium forms. The highest efficiency of nitrogen removal was observed with the passage of electric current at the density of 0.2 A m−2. The efficiency of the denitrification process was over 64% and the nitrification efficiency was 93.4%.

Effect of fermented wastewaters from butter production on phosphates removal in a sequencing batch reactor

This study determined the potential for fermented wastewaters from butter production plant to act as a carbon source to facilitate phosphates removal. Synthetic dairy wastewaters were treated using SBR, with doses of fermented wastewaters. An increase in the fermented wastewater doses were found to improve the effluent quality in respect of phosphates and nitrates. The lowest concentrations of phosphate and nitrates, respectively 0.10 ± 0.04 mg PO(4)-PL(-1) and 1.03 ± 0.22 mg NO(3)-NL(-1), were noted in the effluent from the reactor fed with fermented wastewaters in a dose of 0.25 L d(-1) per 0.45 L d(-1) of wastewaters fed to the reactor. In the case of the two highest doses, an increase in effluent COD was stated. The higher effectiveness resulted from the fact that the introduction of fermented wastewaters caused an increase in the easily-available carbon compounds content and the predominance of acetic acid amongst VFAs available to dephosphatating and denitrifying bacteria.

The effect of volatile fatty acids (VFAs) on nutrient removal in SBR with biomass adapted to dairy wastewater

This study aims to determine the effect of volatile fatty acids on nitrates and orthophosphate removal in a sequencing batch reactor (SBR) with activated sludge biomass adapted to process dairy wastewater. The research also determine whether it is the type of fatty acid applied that is responsible for the effectiveness of denitrification and dephosphatation at varying nitrate:orthophosphate ratios, or whether these processes are additionally affected by the presence of microorganisms that have adapted to the specific carbon composition of the wastewater being treated. At the beginning of an operating cycle SBRs were dosed with VFAs to provide a source of carbon. A comparative analysis was performed of nitrate and orthophosphate removal at initial nitrate concentrations of 1.22, 7.3 and 15.2 mgNNO3·L−1. Doses of fatty acids were approximately 10.5 mgCOD·mg−1PPO4. They consisted of acetic, propionic, butyric, isobutyric, valeric, isovaleric and caproic acids. Increases of nitrate concentration from 1.22 to 15.2 mg NNO3·L−1 were observed to reduce the quantity of removed orthophosphate depending on the fatty acid applied, from 7.2–9.2 mgPPO4·L−1 to 4.5 – 6.7 mgPPO4·L−1. Every increase in the removed nitrates by 5.0 mgNNO3·L−1 was accompanied by a decrease in the removed orthophosphate of around 1 mgPPO4·L−1. The reactor containing acetic acid was found to remove the highest amount of orthophosphate irrespective of the nitrates concentration. Acids present in significant amount in dairy wastewaters (i.e. acetic, propionic and butyric) were more effective source of carbon in the denitrification process compared to low concentration acids.

Recycling potential of air pollution control residue from sewage sludge thermal treatment as artificial lightweight aggregates

Thermal treatment of sewage sludge produces fly ash, also known as the air pollution control residue (APCR), which may be recycled as a component of artificial lightweight aggregates (ALWA). Properties of APCR are typical: high content of Ca, Mg, P2O5, as well as potential to induce alkaline reactions. These properties indicate that ALWA prepared with a high content of APCR may remove heavy metals, phosphorus, and ammonium nitrogen from wastewater with high efficiency. The aim of this preliminary study was to determine the optimal composition of ALWA for potential use as a filter media in wastewater treatment systems. Five kinds of ALWA were produced, with different proportions of ash (shown as percentages in subscripts) in mixture with bentonite: ALWA0 (reference), ALWA12.5, ALWA25, ALWA50, and ALWA100. The following parameters of ALWA were determined: density, bulk density, compressive strength, hydraulic conductivity, and removal efficiency of ions Zn2+, NH4+, and PO43−. Tests showed that ALWA had good mechanical and hydraulic properties, and might be used in wastewater filtering systems. Phosphates and zinc ions were removed with high efficiency (80-96%) by ALWA25-100 in static (batch) conditions. The efficiency of ammonium nitrogen removal was low, <18%. Artificial wastewater treatment performance in dynamic conditions (through-flow), showed increasing removal efficiency of Zn2+, PO43− with a decrease in flow rate.

Analysis of the Sorption Efficiency of Acid, Basic and Direct Dyes Using Chitosan, Fly Ashes Immobilized onto Chitosan and Modified Sawdust Immobilized onto Chitosan as Sorbents

In this study, we analyzed the sorption and desorption of three dyes, namely, acid red 18 (AR18), basic violet 10 (BV10) and direct black 22 (DB22), onto three sorbents of waste material chosen from different branches of industry, namely, chitosan, modified sawdust and fly ash — sorbent 1: chitosan beads, sorbent 2: modified sawdust immobilized onto chitosan and sorbent 3: fly ashes immobilized onto chitosan. Each of these sorbent materials was investigated to determine multiple application feasibility in sorption and desorption cycles. Our study demonstrated that the number of sorption/desorption cycles depended on both the dye and the sorbent. The highest number of sorption/desorption cycles (i.e. n = 7) was achieved for a combination of BV10 and sorbent 2, i.e. modified sawdust immobilized onto chitosan. A comparable effectiveness of six cycles was observed for a combination of AR18 and sorbent 1 (chitosan beads). However, only one sorption/desorption cycle was achieved for sorbent 3, irrespective of the type of dye used.

Hydrogenotrophic denitrification process efficiency and the number of denitrifying bacteria (MPN) in the sequencing batch biofilm reactor (SBBR) with platinum and carbon anodes

ABSTRACT This work reports on the effect of electric current density and anode material (platinum, carbon) on the concentration of oxidized and mineral forms of nitrogen, on physical parameters (pH, redox potential, electrical conductivity) and the number of denitrifying bacteria in the biofilm (MPN). Experiments were conducted under anaerobic conditions without and with the flow of electric current (with density of 79 mA·m−2 and 132 mA·m−2). Results obtained in the study enabled concluding that increasing density of electric current caused a decreasing concentration of nitrate in the reactor with platinum anode (R1) and carbon anode (R2). Its concentration depended on anode material. The highest hydrogenotrophic denitrification efficiency was achieved in R2 in which the process was aided by inorganic carbon (CO2) that originated from carbon anode oxidation and the electrical conductivity of wastewater increased as a result of the presence of HCO3− and CO32− ions. Strong oxidizing properties of the platinum anode (R1) prevented the accumulation of adverse forms of nitrogen, including nitrite and ammonia. The increase in electric current density affected also a lower number of denitrifying bacteria (MPN) in the biofilm in both reactors (R1 and R2). Metal oxides accumulated on the surface of the cathode had a toxic effect upon microorganisms and impaired the production of a hydrogen donor.

Anaerobic rotating disc batch reactor nutrient removal process enhanced by volatile fatty acid addition

RBC effluent needs further treatment because of water-quality standards requiring low nitrogen and phosphorus concentrations. It may be achieved by using reactors with biomass immobilized on the fillings surface as post-denitrification biofilm reactors. Due to the lack of organic matter in treated wastewater, the introduction of external carbon sources becomes necessary. The new attached growth bioreactor – anaerobic rotating disc batch reactor (ARDBR) – was examined as a post-denitrification reactor. The impact of selected volatile fatty acids on nutrient removal efficiency in an ARDBR was studied. The biofilm was developing on totally submerged discs mounted coaxially on a vertical shaft. Acetic, propionic, butyric and caproic acids were applied. Wastewaters were removed from the reactors after 24-h treatment, together with the excess solids. In the ARDBR tank, there was no biomass in the suspended form at the beginning of the treatment process. Acids with a higher number of carbon atoms (butyric and caproic) were the most efficient in denitrification process. The highest phosphorus removal efficiency was noted in the ARDBR with butyric and propionic acids. The lowest unitary consumption of the external source of carbon in denitrification was recorded for acetic acid, whereas the highest one for caproic acid.

PHOSPHORUS REMOVAL IN FILTERS FILLED WITH LWA MADE OF FLY ASHES

The effectiveness of phosphorus removal in vertical-flow filters with double-layer filling composed of light weight aggregate made of fly ashes from sewage sludge thermal treatment (FASSTT LWA) and gravel was determined. Synthetic wastewaters containing 7.36 mg/L of phosphorus were fed into filter columns filled with gravel and FASSTT LWA (gravel was the bed’s lower layer, whereas the top layer of the FASSTT LWA constituted 0, 12, 25, 50, and 100% of the depth of the column) at hydraulic loads from 0.003, to 0.007 m/d. The study demonstrated that the efficiency of phosphorus removal depends on the ratio between the gravel and FASSTT LWA. Phosphorus removal is mainly due to adsorption on the surface of the filter filling. The highest phosphorus removal rate was achieved in the filter column with 50% FASSTT LWA and 50% gravel content, irrespective of the hydraulic load applied. The study confirmed the possibility of using FASSTT LWA to produce granular filling and application as the filling of filter columns used for the treatment of wastewaters containing significant concentration of phosphorus.

Nitrogen Removal in Vertical-Flow Filters Filled with Lightweight Aggregate Made of Fly Ashes and Gravel

AbstractThe effectiveness of nitrogen removal in vertical-flow filters with double-layer filling composed of lightweight aggregate made of fly ashes from sewage sludge thermal treatment (FASSTT LWA) and gravel at a varying hydraulic load was determined. Synthetic wastewaters containing 47  mg/L of total nitrogen (TN) were fed into 15 filter columns filled with gravel and FASSTT LWA (gravel was the bed’s lower layer, whereas the top layer of the FASSTT LWA constituted 0, 12, 25, 50, and 100% of the depth of the column) at hydraulic loads of 3, 5, and 7  mm/day. The study demonstrated a significant TN removal by the filters, which was accompanied by a high concentration of NO3-N in the effluent. The results point to differentiated effectiveness of NH4-N removal by both the FASSTT LWA and gravel. The highest TN removal rate reaching up to 74.93% was achieved in the filter column with 100% FASSTT LWA content, irrespective of the hydraulic load applied.