Optimal integration of vacuum UV with granular biofiltration for advanced wastewater treatment: Impact of process sequence on CECs removal and microbial ecology.

This study explored process synergies attainable by integrating a vacuum ultraviolet-based advanced oxidation process with biofiltration. A comparison using granular activated carbon or granular zeolite as filtration media were examined in context of advanced wastewater treatment for potable reuse. Six biofiltration columns, three with granular activated carbon and three with granular zeolite, were operated in parallel and batch-fed daily with nitrified secondary effluent. After achieving a pseudo-steady state through the filter columns, vacuum ultraviolet treatment was applied as pre-treatment or as post-treatment, at two different applied energies (i.e., VUV-E1=1 kWh/m3 and VUV-E10=10 kWh/m3). Once granular activated carbon had transitioned to biologically activated carbon, as determined based on soluble chemical oxygen demand removal, adsorption was still observed as the main mechanism for contaminants of emerging concern and nitrate removal. Vacuum ultraviolet pre-treatment markedly improved contaminants of emerging concern removal through the integrated system, achieving 40% at VUV-E1 and 90% at VUV-E10. When applied as post-treatment to zeolite column effluents, VUV-E1 and VUV-E10 further increased contaminants of emerging concern removal by 20% and 90%, respectively. In the zeolite system, vacuum ultraviolet pre-treatment also increased soluble chemical oxygen demand removal efficiency, indicating that higher energy vacuum ultraviolet increased biodegradability. Total prokaryotes were two-fold more abundant in biologically activated carbon than in zeolite, with vacuum ultraviolet pretreatment markedly affecting microbial diversity, both in terms of richness and composition. Media type only marginally affected microbial richness in the biofilters but showed a marked impact on structural composition. No clear relationship between compositional structure and depth was observed.

Modeling the impact of food wastes on wastewater treatment plants.

Food waste (FW) enriched with readily biodegradable organics can enhance biological nutrient removal (BNR), and biogas production. This study conducted extensive wastewater treatment simulations using BioWin software to predict the impact of food waste on nutrient removal, biogas generation, and energy balance. A total of 114 scenarios were tested to simulate different treatment technologies i.e. conventional activated sludge, Modified Ludzack-Ettinger (MLE), anaerobic-anoxic-aerobic (A2O), Bardenpho, and 2nd generation BNR technologies. The simulations also included sidestream treatment for nitrogen removal, as well as mainstream partial nitrification based on BNR. The results showed that FW addition enhanced nitrogen removal and decreased effluent nitrogen for BNR processes by 3.6-7.9 mg/L for MLE, 0.6-1.3 mg/L for A2O, and 1-2.3 mg/L for Bardenpho. In addition, FW addition decreased net operational cost by 26%-63% for BNR processes operating at mainstream conventional dissolved oxygen (DO) of 2 mg/L, 24%-78% for partial nitrification system, 29%-54% for sidestream, and 23%-76% for sidestream with mainstream partial nitrification process. The total net energy benefit considering both the net change in aeration energy and methane energy for a typical 37,854 m3/d or 10 MGD plant increased with FW addition by 3300-7900 kWh/d with a variation between BNR types, due to a substantial increase in methane production. Carbon diversion scenarios showed that the higher primary treatment efficiencies decreased the net operational cost and increased net energy gain.

Synergism of co-digestion of food wastes with municipal wastewater treatment biosolids.

Five semi-continuous flow anaerobic digesters treating a mixture of food waste (FW) and municipal biosolids (primary sludge and thickened wasted activated sludge) at an solids retention time (SRT) of 20 days and different blend ratios i.e. 0, 10%, 20%, 40% by volume with the fifth digester treating only biosolids at the same COD/N ratio as the 40% FW digester were operated to investigate co-digestion performance. Sixty days of steady-state operation at organic loading rates (OLR) of 2.2-3.85kgCOD/m3/d showed that COD removals were higher for the three co-digesters than for the two municipal biosolids digesters i.e. 61-69% versus 47-52%. Specific methane production per influent CODs were 1.3-1.8 folds higher in co-digestion than mono-digestion. The first-order COD degradation kinetic constants for co-digestion were more than double the mono-digestion. Additional methane production through synergism accounted for a minimum of 18-20% of the overall methane production. The estimated non-biodegradable fraction of the FW particulate COD was 7.3%. However, the co-digesters discharged 1.23-1.64 times higher soluble nitrogen than the control.

Mitochondrial Neurogastrointestinal Encephalopathy: Clinical, Biochemical and Molecular Study in Three Egyptian Patients.

Background: Mitochondrial Neurogastrointestinal Encephalopathy syndrome is a rare autosomal recessive disorder. The disease is caused by mutations in the thymidine phosphorylase gene. This article reports the clinical, biochemical and molecular findings in three Egyptian patients with Mitochondrial Neurogastrointestinal Encephalopathy sundrome from two different pedigrees. Subjects and Methods: The three patients were subjected to thorough neurologic examination. Brain Magtnetic Resonance Imaging. Histochemical and biochemical assay of the mitochondrial respiratory chain complexes in muscle homogenate was performed (1/3). Thymidine Phosphorylase enzyme activity was performed in 2/3 patients and Thymidine Phosphorylase gene sequencing was done (2/3) to confirm the diagnosis. Results: All patients presented with symptoms of severe gastrointestinal dysmotility with progressive cachexia, neuropathy, sensory neural hearing loss, asymptomatic leukoencephalopathy. Histochemical analysis of themuscle biopsy revealed deficient cytochrome C oxidase and mitochrondrial respiratory chain enzyme assay revealed isolated complex 1 deficiency (1/3). Thymidine Phosphorylase enzyme activity revealed complete absence of enzyme activity in 2/3 patients. Direct sequencing of Thymidine Phosphorylase gene revealed c.3371 A>C homozygous mutation. Molecular screening of both families revealed heterozygous mutation in both parents and 4 siblings. Conclusions: Mitochondrial Neurogastrointestinal Encephalopathy syndrome is a rare mitochondrial disorder with an important diagnostic delay. In case of pathogenic mutations in Thymidine Phosphorylase gene in the family, carrier testing and prenatal diagmosis of at risk members is recommended for early detection. The possibility of new therapeutic options makes it necessary to diagnose the disease in an early state.

Characterization of typical household food wastes from disposers: fractionation of constituents and implications for resource recovery at wastewater treatment.

Food wastes with typical US food composition were analyzed to characterize different constituents in both particulate and soluble phases i.e., solids, chemical oxygen demand (COD), 5-day biochemical oxygen demand (BOD), nitrogen (N), phosphorus (P). Relationships between various pollutants were also investigated using 50 samples. One gram of dry food waste generated 1.21 g COD, 0.58 g BOD5, 0.36 g Total SS, 0.025 g Total N, and 0.013 g Total P. Distribution of constituents between particulate and aqueous phases indicated that 40% of COD and 30% of nitrogen were present in soluble form. Relative mass ratios of COD and nitrogen to solids were three to five times higher in particulates than in aqueous phase. However, COD/N ratios were higher in aqueous form than particulates at 63:1 versus 42:1. Detailed relationships between parameters showed that COD, nitrogen, and phosphorus in particulates are 200%, 3.6%, and 3.5% of the volatile suspended solids.

Treatment of high-strength pet food wastewater using two-stage membrane bioreactors.

A two-stage membrane bioreactor was used to treat dissolved-air-flotation pretreated, high-strength pet food wastewater characterized by oil and grease concentrations of 50 000 to 82 000 mg/L and total chemical oxygen demand (COD) and five-day biochemical oxygen demand (BOD5) concentrations of 100 000 and 80 000 mg/L, respectively, to meet stringent surface discharge criteria (i.e., BOD5, total suspended solids [TSS], and ammonium-nitrogen [NH4(+)-N] of < 10 mg/L at an overall hydraulic retention time of 6.3 days). Organic contaminants were removed primarily in the first stage, followed by almost complete removal of ammonia in the second stage. Despite a rise in poorly biodegradable COD in the second stage, overall removal of TSS, BOD5, COD, and ammonia was 100, 99.9, 95.2, and 99.7%, respectively, thus readily achieving the required criteria. Consistent nitrite accumulation over a period of more than 100 days, even at dissolved oxygen concentrations of more than 2.5 mg/L, was remarkable. A residual alkalinity requirement for nitrification was quantified. Membrane performance was extensively studied in this work.

Biodegradation kinetics of high strength oily pet food wastewater in a membrane-coupled bioreactor (MBR).

Aerobic respirometric experiments were conducted at a temperature of 40 degrees C to determine biokinetic parameters describing growth and decay of aerobic biomass acclimatized in a membrane-coupled bioreactor (MBR). The kinetic parameters were determined with the volatile fatty acids (VFA) acetic acid and propionic acid as substrates as well as the soluble fraction of a high strength rendering wastewater as substrate. The oxygen uptake rate (OUR) and cumulative oxygen uptake (OU) recorded during the experiments were fitted to Monod kinetic model to obtain true yield (Y(t)), intrinsic maximum substrate removal (k), half-saturation constant (K(s)) and endogenous decay coefficient (k(d)). K(s) were determined to be 181, 271 and 806 mg COD l(-1) and k as 1.89, 1.08 and 0.85 mg COD mg VSS(-1)h(-1) for acetate, propionate and rendering wastewater, respectively. The continuous-flow MBR was operated under two HRT conditions, 10 and 5 d, attaining high BOD removal efficiencies of 99% and 87%, respectively. The observed yield in the MBR was 0.03 g VSS g(-1)COD.

Kinetic modeling of aerobic biodegradation of high oil and grease rendering wastewater.

Batch scale activated sludge kinetic studies were undertaken for the treatment of pet food wastewater characterized by oil and grease concentrations of up to 21,500 mg/L, COD and BOD concentrations of 75,000 and 60,000 mg/L, respectively as well as effluent from the batch dissolved air flotation (DAF) system. The conducted kinetics studies showed that Haldane Model fit the substrates and biomass data better than Monod model in DAF-pretreated wastewater, while the modified hydrolysis Monod model better fit the raw wastewater kinetic data. For the DAF pretreated batches, Haldane Model kinetic coefficients k, K(S), Y and Ki values of 1.28-5.35 g COD/g VSS-d, 17,833-23,477 mg/L, 0.13-0.41 mg VSS/mg COD and 48,168 mg/L, respectively were obtained reflecting the slow biodegradation rate. Modified hydrolysis Monod model kinetic constants for the raw wastewater i.e., k, K(S), Y, and K(H) varied from 1-1.3 g COD/g VSS-d, 5580-5600 mg COD/l, 0.08-0.85 mg VSS/mg COD, and 0.21-0.66 d(-1), respectively.

A novel two-stage MBR denitrification process for the treatment of high strength pet food wastewater.

A novel paradigm using pre-denitrification process is presented to optimize an existing system of two-stage MBRs treating high strength pet food wastewater. Successive reduction of organics in the 1st stage and almost complete nitrification in the 2nd stage generated effluent meeting stringent surface discharge criteria i.e. BOD5, TSS and NH4+ -N of < 10 mg/L at an overall HRT of 6.3 days. Pre-anoxic zone was created by a submerged coil in the path of influent to the 1st stage. Final effluent and the 1st stage mixed liquor were recirculated to the coil. With prevailing high denitrification rates, more than 94% of the recirculated nitrates were denitrified in less than 15 min of effective anoxic residence time. At a recycle ratio of 3:1, total nitrogen was reduced by 84%, aeration energy by 25% and the external alkalinity requirement by 65%, enhancing economical viability of the system.

Conventional and thermophilic aerobic treatability of high strength oily pet food wastewater using membrane-coupled bioreactors.

Although thermophilic treatment systems have recently gained considerable interest, limited information exists on the comparative performances of membrane-coupled bioreactors (MBR) at thermophilic and conventional conditions. In this study aerobic MBRs operating at room temperature (20 degrees C) and at lower thermophilic range (45 degrees C) were investigated for the treatment of dissolved air flotation (DAF) pretreated pet food wastewater. The particular wastewater is characterized by oil and grease (O & G) concentrations as high as 6 g/L, COD of 51 g/L, BOD of 16 g/L and volatile fatty acid (VFA) of 8.3 g/L. The performances of the two systems in terms of COD, BOD and O & G removal at varying hydraulic retention time (HRT) are compared. COD removal efficiencies in the thermophilic MBR varied from 75% to 98% and remained constant at 94% in the conventional MBR. The O & G removal efficiencies were 66-86% and 98% in the thermophilic and conventional MBR, respectively. Interestingly, high concentrations of VFA were recorded, equivalent to 50-73% of total COD, in the thermophilic MBR effluent. The observed yield in the thermophilic MBR was 40% of that observed in the conventional MBR.

Simultaneous carbon and nitrogen removal in anoxic-aerobic circulating fluidized bed biological reactor (CFBBR).

Biological nutrient removal (BNR) in municipal wastewater treatment to remove carbonaceous substrates and nutrients, has recently become increasingly popular worldwide due to increasingly stringent regulations. Biological fluidized bed (BFB) technology, which could be potentially used for BNR, can provide some advantages such as high efficiency and a compact structure. This work shows the results of simultaneous elimination of organic carbon and nitrogen using a circulating fluidized bed biological reactor (CFBBR, which has been developed recently for chemical engineering processes. The CFBBR has two fluidized beds, running as anoxic and aerobic processes to accomplish simultaneous nitrification and denitrification, with continuous liquid recirculation through the anoxic bed and the aerobic bed. Soluble COD concentrations in the effluent ranging from 4 to 20 mg l(-1) were obtained at varying COD loading rates; ammonia nitrogen removal efficiencies averaged in excess of 99% at a minimum total hydraulic retention time (HRT) of 2.0 hours over a temperature range of 25 degrees C to 28 degrees C. Effluent nitrate nitrogen concentration of less than 5 mg l(-1) was achieved by increasing effluent recycle rate. No nitrite accumulation was observed either in the anoxic bed or in the aerobic bed. The system was able to treat grit chamber effluent wastewater at a HRT of 2.0 hours while achieving average effluent BOD, COD, NH3-N, TKN, nitrates, total phosphate, TSS and VSS concentrations of 10 mg l(-1), 18 mg l(-1), 1.3 mg l(-1), 1.5 mg l(-1), 7 mg l(-1), 2.0 mg l(-1), 10 mg l(-1) and 8 mg l(-1) respectively. The CFBBR appears to be not only an excellent alternative for conventional activated sludge type BNR technologies but also capable of processing much higher loadings that are suitable for industrial applications.

The treatability study of high strength pet food wastewater: a continuous flow aerobic system performance evaluation.

This paper presents continuous flow two stage activated sludge treatability studies for the treatment of pet food wastewaters characterized by oil & grease concentration of 50,000-66,000 mg l(-1), total COD & BOD concentrations of 100,000 mg l(-1) and 80,000 mg l(-1), respectively. A pre-treatment system, dissolved air flotation (DAF) achieved 97-99% reduction in oil and grease down to about 400-800 mg l(-1). The pilot experimental results showed that for the DAF pretreated effluent, 97% soluble COD removal efficiency can be achieved by using two stage conventional activated sludge system at a 6-7 days HRT and applied initial soluble COD to biomass ratio of 1.17 mg COD mg VSS. Meanwhile, the system achieved 99.9% soluble BOD removal. Analysis of system kinetics indicated that this particular wastewater is very difficult to biodegrade, with an extremely high half velocity constant "Ks" of 5800 mg l(-1). The research showed the potential applications of activated sludge systems for the treatment of high oil and grease wastewater.

Treatability and kinetics studies of mesophilic aerobic biodegradation of high oil and grease pet food wastewater.

In this work, batch activated sludge studies were investigated for the treatment of raw pet food wastewater characterized by oil and grease concentrations of 50,000-66,000 mg/L, COD and BOD concentrations of 100,000 and 80,000 mg/L, respectively, as well as effluent from an existing anaerobic digester treating the aforementioned wastewater. A pre-treatment process, dissolved air flotation (DAF) achieved 97-99% reduction in O&G to about 400-800 mg/L, which is still atypically high for AS. The batch studies were conducted using a 4-L bioreactor at room temperature (21 degrees C) under different conditions. The experimental results showed for the DAF pretreated effluent, 92% COD removal efficiency can be achieved by using conventional activated sludge system at a 5 days contact time and applied initial soluble COD to biomass ratio of 1.17 mg COD/mg VSS. Similarly for the digester effluent at average oil and grease concentrations of 13,500 mg/L, activated sludge affected 63.7-76.2% soluble COD removal at 5 days. The results also showed that all kinetic data best conformed to the zero order biodegradation model with a low biomass specific maximum substrate utilization rate of 0.168 mg COD/mg VSS day reflecting the slow biodegradability of the wastewater even after 99% removal of oil and grease.