Total Kjeldahl Nitrogen Removal Research Articles

‘Solar septic tank’: evaluation of innovative decentralized treatment of blackwater in developing countries

Abstract An innovative decentralized wastewater treatment system, namely the ‘Solar Septic Tank (SST)’, was constructed and tested at the household scale in a community in central Thailand. This study aimed to investigate the long-term performance of the SST in treating blackwater subject to year-round variation. Results of the 3-year continuous operation and monitoring showed significant improvement in the SST effluent quality with the potential to minimize environmental problems and public health risks. The SST achieved significantly higher total chemical oxygen demand, soluble chemical oxygen demand, total biochemical oxygen demand (TBOD), soluble biochemical oxygen demand, total kjeldahl nitrogen, total solid and total volatile solid removal efficiencies than a conventional septic tank (CST). The average TBOD concentration of the SST effluent was 150 ± 75 mg/L, meeting the Thai discharge standard (less than 200 mg/L of TBOD), while the average TBOD concentration of the CST was 240 ± 140 mg/L, higher than the Thai discharge standard. The Escherichia coli inactivation in the SST was 1–2 log reduction more than that in the CST. The removal efficiencies of TBOD and pathogens exhibited positive correlation with the ratios of the SST temperature.

Zeolite-intermittent cycle moving bed air-lift bioreactor (Zeo-ICMBABR) for composting leachate treatment; simultaneous COD, nitrogen and phosphorous compounds removal.

Anaerobically pretreated composting leachate contains high ammonia load and soluble organic matter, which requires further treatment. In this study, simultaneous removal of COD, nitrogen, and phosphorus compounds from anaerobically pretreated composting leachate investigated by using an intermittent cycle moving bed airlift bioreactor (ICMBABR) supported by zeolite as a biofilm. The efficiency of COD, Total Kjeldahl Nitrogen (TKN), and phosphorous removal and contaminants profile during the process, and the mass balances were analyzed. A multilayer design used for the experimental design, and the effect of four variables including hydraulic retention times (4, 6, 8h), the zeolite ratios (20, 35, 50%), the influent COD concentration (1, 2, and 3g/L) and aeration duration (64, 73, and 82%) investigated by Response Surface Methodology (RSM). According to the results and process profile the sequence of anoxic and aerobic conditions, presence of the anaerobic zone in the bottom of the reactor, as well as the use of zeolite as adsorbent media, significantly allowed the simultaneous removal of COD (99%), TKN (95%), and total phosphorus compounds (90%) from anaerobically pretreated composting leachate and favorable potential to remove nitrogen compounds by high efficiency (79%) through simultaneous nitrification and denitrification (SND).

Influence of rain events on the efficiency of a compact wastewater treatment plant: a case study on a university campus aiming water reuse for agriculture.

In this study, the efficiency of contaminant removal from a compact wastewater treatment plant (CWTP) in a university campus under different rain conditions was evaluated. Wastewater samples were collected weekly for 1year and the physicochemical parameters were monitored. Removal efficiency higher than 77%, reaching values above 95% for samples with lower wastewater flow rates, was found for biological oxygen demand (BOD) and total and fecal coliforms. The pH values remained in the range of 6.0-8.0. However, pH values below 6.8 impaired the nitrification rate and, therefore, the removal of total Kjeldahl nitrogen (TKN) and ammonia was lower than the expected, with concentration values above those set by the Brazilian regulation for wastewater discharge. The results show that the flow rate of wastewater at the entrance of the CWTP is directly related to the rain events, thus affecting its efficiency, mainly in the removal of total solids, turbidity, and organic matter. The assessment of the treated wastewater reuse on site for agricultural purposes showed to be a prominent and more sustainable alternative regarding the discharge of wastewater into water bodies.

Modified electrochemical processes for industrial-scale treatment of wastewater having high TKN content

Electrochemical phenomena were implemented to treatment of industrial wastewater containing high nitrogen concentrations. Organic nitrogen and ammonia, measured by Total Kjeldahl Nitrogen (TKN), raise concerns for most conventional wastewater treatment plants having limited capability of their removal. To avoid contamination of ecosystems with an excessive nitrogen discharge, environmental regulations do not permit for dilution of effluent containing nitrogenous compounds but rather require their adequate removal. This is a challenge for many industrial facilities producing wastewater containing TKN at the level of thousands milligrams per liter. The studied wastewater comprised such TKN along with a significant concentration of ferrous ions in a dissolved form. It was found that ferrous ions in so high concentrations could be advantageous as they provide a platform for designing a sustainable process. In this study, combined electrochemical advanced oxidation and modified electro-Fenton like process was designed and validated at three distinct scales with the goal of finding a scalable solution for TKN removal. An Electro-Fenton Sequential Batch Reactor (EF-SBR) was developed to facilitate the removal efficiency of ammonia and TKN, by more than 99% and 98%, respectively. The reproducibility of the process was validated through several SBR cycles. Moreover, the implementation of EF-SBR permitted to optimize the specific energy consumption and resulted in a pronounced decrease in sludge production.

Concomitant wastewater treatment with lipid and carotenoid production by the oleaginous yeast Rhodosporidium toruloides grown on brewery effluent enriched with sugarcane molasses and urea

In this study, secondary brewery wastewater (SBWW) supplemented with sugarcane molasses (SCM) was used for SBWW treatment with concomitant lipid and carotenoid production by the yeast Rhodosporidium toruloides NCYC 921. In order to improve the biomass production, ammonium sulfate, yeast extract and urea were tested as nitrogen sources. Urea was chosen as the best low-cost nitrogen source. A fed-batch cultivation was carried out with SBWW supplemented with 10 g L−1 of sugarcane molasses as carbon source, and 2 g L−1 of urea as nitrogen source. A maximum biomass concentration of 42.5 g L−1 was obtained at t = 126.5 h and the maximum biomass productivity was 0.55 g L−1 h−1 at t = 48.25 h. The maximum lipid content was 29.9 % w/w (DCW) at t = 94 h of cultivation and the maximum carotenoid content was 0.23 mg g−1 at 120 h of cultivation. Relatively to the SBWW treatment, after the batch phase, 45.8 % of total Kjeldahl nitrogen removal, 81.7 % of COD removal and 100 % of sugar consumption were observed. Flow cytometry analysis revealed that 27.27 % of the cells had injured membrane after the inoculation. This proportion was reduced to 10.37 % at the end of the cultivation, indicating that cells adapted to the growth conditions.

Nutrient Transformation and Removal from Treated Wastewater Recycled Via Aquifer Storage and Recovery (ASR) in a Carbonate Aquifer

Wastewater reuse coupled to managed aquifer recharge (MAR) provides a means to store and reuse treated wastewater (TWW) year-round. Determining the fate of nutrients in the subsurface during MAR remains challenging for environmental regulation due to the interaction of the MAR source water with site specific aquifer conditions. To facilitate the understanding of natural treatment processes, this study uses operational monitoring data from a full-scale aquifer storage and recovery (ASR) scheme using TWW to assess nutrient (N and P) transformation and fate. Analysis of median water quality injected into and recovered from the ASR wells for two complete ASR cycles (June 2014 to March 2016) was used to describe the removal of nutrients in an anoxic carbonate aquifer. Total nitrogen (TN) removal was dominated by redox processes, with median removal of 40 to 60% for TN and nitrate (the dominant N species) and higher removal of ammonia (95%) and total Kjeldahl nitrogen (TKN) (70%). Total phosphorous (TP) removal was also observed (~ 90%) due to sorption (filterable reactive phosphorous median removal of ~ 80%). A 40% increase in median salinity was evident within each ASR cycle due to recovery of the entire volume of injected water each year (ambient groundwater is 200% higher in TDS, on average). A reduction in salinity of the recovered water could be achieved by leaving a residual of source water in the aquifer to create a buffer zone between the ambient groundwater and the fresher source water.

Proposal of upgrading Isfahan north wastewater treatment plant: An adsorption/bio-oxidation process with emphasis on excess sludge reduction and nutrient removal

There is a rising challenge in managing the activated sludge process due to excess sludge disposal from the wastewater treatment plant and inadequate effluent quality due to the stricter standard of effluent quality. Hence, the incorporation of oxic-settling-anoxic process and ultrasonic waves in the return sludge line was proposed to assess the excess sludge reduction and nutrient removal in the adsorption/bio-oxidation activated sludge process as a proposal upgrading. The results indicated that sludge production from adsorption/bio-oxidation process could be reduced using oxic-settling-anoxic and ultrasonic by 50% at each studied mixed liquor suspended solids level. Compared to the adsorption/bio-oxidation process, the total and soluble chemical oxygen demand removal efficiencies in adsorption/bio-oxidation process with oxic-settling-anoxic and ultrasonic slightly decreased suggesting a lysis phenomenon. During the operation of adsorption/bio-oxidation process with oxic-settling-anoxic and ultrasonic, the total Kjeldahl nitrogen removal efficiency improved in A and B stages, with 38.3 ± 8.1% and 83.1 ± 6.5% versus 36.8 ± 14.5% and 75.1 ± 7.3%, respectively. According to the stoichiometric calculations, in B stage of adsorption/bio-oxidation process with oxic-settling-anoxic and ultrasonic, the soluble available ultimate biochemical oxygen demand and net NO3 produced for denitrification were 69.5 and 43.8 mg/L, respectively. Overall, the experimental data revealed that the adsorption/bio-oxidation process with oxic-settling-anoxic and ultrasonic produced lower excess biological sludge and better total Kjeldahl nitrogen removal efficiency compared to the adsorption/bio-oxidation system alone.

Nutrient Removals by Pinestraw Harvesting in Slash Pine Plantations in Florida

Abstract Pinestraw harvesting is an important industry in the southeastern United States. There is a need to understand how fertilization can be used efficiently to sustain or increase long-term pinestraw yields and avoid adverse environmental consequences. The effects of fertilization on needlefall nutrient concentrations, pinestraw yields, and nutrient removals on soils with contrasting soil nutrient sorption potential (Entisol vs. Ultisol) were compared using two midrotation slash pine plantations in North Florida. Diammonium phosphate was applied at 0, 144, 430, or 718 kg ha–1 in the spring of 2009 and 2010. Pinestraw was harvested annually in 2009–12. Needlefall mass, pinestraw yields, total Kjeldahl nitrogen concentrations in needlefall and pinestraw, and total Kjeldahl nitrogen, P, K, Ca, and Mg removals increased with fertilization. Diammonium phosphate at 718 kg ha–1 year–1 increased pinestraw yield over the control by 37 and 35 percent 2 years after the second fertilization, and by 11 percent (from 21.5 to 23.8 Mg ha–1) and 12 percent (from 25.0 to 28.1 Mg ha–1) over the 4-year control totals, at Entisol and Ultisol sites, respectively. Differences between sites were larger than fertilization response for most variables. Yields, nutrient concentrations, and removals were higher at the more fertile Ultisol than Entisol and, at both sites, higher than most reported in the literature.

Improved Wastewater Treatment by Combined System of Microbial Fuel Cell with Activated Carbon/TiO2 Cathode Catalyst and Membrane Bioreactor

A two-stage continuous process was developed for treating medium-strength wastewater combining microbial fuel cell (MFC) using activated carbon (AC)/TiO2 composite as cathode catalyst and submerged membrane bioreactor (MBR). Synthetic wastewater, having total chemical oxygen demand (COD) of around 3 g/L, was introduced first in the anodic chamber of MFC in a continuous mode of operation followed by aerobic MBR. Submerged hollow-fibre ultra-filtration membrane assembly was attached to draw permeate from MBR. The electrical performance of MFC was evaluated by polarisation, which showed a maximum volumetric power density of 1.02 W/m3 with much lower whole-cell internal resistance of 10 Ω. The coulombic efficiency of MFC was estimated to be 0.31%, demonstrating AC/TiO2 composite as a promising cathode catalyst for applications in MFC. The permeate of MFC–MBR system showed 98.3 ± 0.3% and 81.9 ± 1.8% of COD and total Kjeldahl nitrogen removal efficiency, respectively, producing permeate with total suspended solids concentration of less than 5 mg/L. Thus, a two-stage reliable process for treatment of wastewater is demonstrated using integrated MFC–MBR for generating high-quality recyclable effluent and facilitating recovery of bio-electricity.

TiO2/Activated carbon photo cathode catalyst exposed to ultraviolet radiation to enhance the efficacy of integrated microbial fuel cell-membrane bioreactor

Two integrated microbial fuel cell-membrane bioreactor (MFC-MBR) were developed to treat medium-strength wastewater with simultaneous power generation. Both the systems were operated with photo-sensitized cathode (with TiO2-Activated carbon) with one irradiated by UV-A light (MMT-UV), while the other was not in direct contact with any light sensitization (MMT). In polarization, MMT-UV exhibited higher maximum power density of 494 mW m−2 as compared to MMT (239 mW m−2). Normalized energy recovery was also estimated to be 0.122 kWh m−3 for MMT-UV and 0.058 kWh m−3 for MMT. On the other hand, overall chemical oxygen demand and total Kjeldahl nitrogen removal efficiency were almost similar and high enough ( ̴ 95% and 86–90%, respectively) for these type of two-stage wastewater treatment systems with very less footprint. Hence, the integrated MFC-MBR with TiO2-Activated carbon as cathode-catalyst in presence of UV showed excellent treatability of wastewater with simultaneous bioelectricity generation to reduce the overall energy demand.

Simultaneous removal of sulfur and nitrogen compounds with methane production from concentrated latex wastewater in two bioreactor zones of micro‐oxygen hybrid reactor

AbstractBACKGROUNDA micro‐oxygen hybrid reactor (MOHR), a two‐zone reactor with suspended sludge zone (SZ) and attached biofilm zone (AZ) at its lower and upper parts respectively, was applied to simultaneously remove sulfur and nitrogen compounds with methane production from concentrated latex wastewater with high concentrations of sulfate (1200 mg L−1) and ammonium (235 mg L−1). Microbial community structures coupled with microbial activities were analyzed and discussed for clarifying relationships of microorganisms in both zones of the MOHR.RESULTSThe operating dissolved oxygen in the MOHR was controlled at 0.10–0.15 and 0.05 mg L−1 in the SZ and AZ respectively at various loading rates (LRs) and hydraulic retention times (HRTs). The average optimal overall performances of the MOHR for sulfate (SO42−), total Kjeldahl nitrogen (TKN) and chemical oxygen demand (COD) removal efficiencies were 90.3, 67.8 and 93.0% respectively at HRT 10 days. Elemental sulfur and nitrogen gas were evaluated as major end‐products at 90.2 and 67.9% respectively, with 0.27 L CH4 g−1 CODremoved of methane selectivity. The genera Desulfobulbus and Dongia as well as Thiobacillus denitrificans served as dominant microorganisms in biological sulfate removal. The largest abundance belonged to denitrifying microorganisms with nitrous oxide reductase (nosZ) as target gene.CONCLUSIONThe MOHR achieved high performance in simultaneous removal of sulfur and nitrogen compounds along with methane production at HRT 10 days. Microorganisms involved in sulfur and nitrogen compound removal processes were more prevalent in the SZ than in the AZ, whereas methanogenic activity was higher in the AZ than in the SZ. © 2019 Society of Chemical Industry

Treatment of Liquid Phase of Digestate from Agricultural Biogas Plant in a System with Aerobic Granules and Ultrafiltration

Management of digestate from manure co-digestion with a very high chemical oxygen demand (COD) to nitrogen ratio and high nitrogen loads are a major bottleneck in the development of agricultural biogas plants. The liquid phase of digestate mixed with municipal wastewater was treated in aerobic granular sludge batch reactors at cycle lengths (t) of 6 h (GSBR6h), 8 h (GSBR8h), and 12 h (GSBR12h), corresponding to nitrogen loads of 1.6, 1.2, and 0.8 g/(L·d). Thauera sp., Lacibacter sp., Thermanaerothrix sp., and Planctomyces sp. predominated in granules favoring effective granule formation and nitrogen removal. Increasing cycle lengths (t) significantly decreased proteins in soluble fraction of extracellular polymeric substances (EPS) in granules and increased polysaccharides in tightly bound EPS that resulted in higher granule diameters and higher COD removal. In GSBR6h, heterotrophic nitrification/denitrification was very efficient, but ammonium was fully oxidized in the last hour of the cycle. So in further studies, the effluent from GSBR8h was subjected to ultrafiltration (UF) at transmembrane pressures (TMPs) of 0.3, 0.4, and 0.5 MPa. A GSBR8h-UF system (TMP of 0.4 MPa) ensured full removal of total Kjeldahl nitrogen (TKN), suspended solids, and substantial reduction of COD and color with good permeate flux. The NOx-rich (about 250 mg/L), clear permeate can be reused in line with assumptions of modern circular economy.

Use of broken brick to enhance the removal of nutrients in subsurface flow constructed wetlands receiving hospital wastewater.

Eight horizontal subsurface flow pilot scale artificial wetlands were constructed to evaluate the effectiveness of broken brick to remove nutrients from hospital wastewater. The average total suspended solids (TSS), 5-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), NH4-N, NO3-N, and phosphate percent removal efficiency of constructed wetlands were, respectively, 93.2%, 90.4%, 83.7%, 64%, 64.3%, 52.1% and 56.1% in the dry season and 89.7%, 85.8%, 82.9%, 66%, 62.7%, 56.1% and 59.5% in the rainy season. Broken brick bed wetlands provide better removal efficiency of TKN, ammonia, nitrate, and phosphate with an average removal rate of 73%, 71.3%, 79.6% and 77.1% in the dry season and 74.7%, 70.7%, 70.9% and 73.6% in the rainy season, respectively, and it provides better adsorption sites for ammonium, nitrate, and phosphate. Typha with the broken brick bed significantly improved (P < 0.05) the treatment performance of the constructed wetland systems for the removal of ammonia, nitrate, and phosphate. The seasonal variation could not significantly influence the removal of all the pollutants, but better performance of nitrate and phosphate was achieved in a dry season. Use of locally available broken brick as a substrate media can increase the nutrient removal efficiency of wetlands at a cheaper cost when applied in full scale constructed wetlands.

Laboratory-scale investigation on the role of microalgae towards a sustainable treatment of real municipal wastewater.

Engineered microalgal-bacteria consortia are an attractive solution towards a low-cost and sustainable wastewater treatment that does not rely on artificial mechanical aeration. In the research conducted for this study, a bench-scale photo-sequencing-batch reactor (PSBR) was operated without external aeration. A spontaneous consortium of microalgae and bacteria was developed in the PSBR at a concentration of 0.8-1.7 g TSS/L. The PSBR ensured removal efficiency of 85 ± 8% for chemical oxygen demand (COD) and 98 ± 2% for total Kjeldahl nitrogen (TKN). Nitrogen balance revealed that the main mechanisms for TKN removal was autotrophic nitrification, while N assimilation and denitrification accounted for 4% and 56%, respectively. The development of dense microalgae-bacteria bioflocs resulted in good settleability with average effluent concentration of 16 mgTSS/L. The ammonium removal rate was 2.9 mgN L-1 h-1, which corresponded to 2.4 mgN gTSS-1 h-1. Although this specific ammonium removal rate is similar to activated sludge, the volumetric rate is lower due to the limited total suspended solids (TSS) concentration (three times less than activated sludge). Therefore, the PSBR footprint appears less competitive than activated sludge. However, ammonium was completely removed without artificial aeration, resulting in a very cost-effective process. Only 50% of phosphorus was removed, suggesting that further research on P uptake is needed.

Optimization of nitrogen and phosphorus removal from pig slaughterhouse and packing plant wastewater through electrocoagulation in a batch reactor

This work evaluated the removal of total Kjeldahl nitrogen (TKN) and total phosphorus (P) through electrocoagulation and used aluminum electrodes to optimize the potential differential (pd) and hydraulic retention time (HRT) variables in a batch reactor. The experimental design used was Rotatable Central Composite Design (RCCD). The application of the electrocoagulation in the treatment of effluents from pig slaughterhouses and packing plants proved to be efficient in relation to the removal of TKN and total phosphorus, obtaining maximum efficiency equal to 67.15% and 99%, respectively. The maximum TKN removal value was found in Test 12, where treatment conditions were 30 minutes for HRT and 20 volts for pd, which corresponds to 0.86 A of electric current and a current density of 17.2 mA cm-2. For P, the only test that removed below 99% was the first. Through statistical analyses, it was only possible to obtain a mathematical model for TKN removal. While the response surface graph did not present a defined range of the best conditions for the independent variables, it was possible to observe the tendency for better removal, a wide range of pd and values over 30 minutes for retention time.

Soft drink industry wastewater treatment in microwave photocatalytic system – Exploration of removal efficiency and degradation mechanism

The present study investigated the photolytic and photocatalytic treatment of soft drink industry wastewater (SDIW) in presence of microwave (MW) irradiation. The treatment efficiency was investigated in terms of removal rate of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN) and total phosphate (TP) in microwave photolysis (MWP) system, MW photocatalytic system with one and two electrodeless discharge lamp (EDL), denoted as MWPC-1 and MWPC-2 respectively. The MWPC-2 system showed highest efficiency with a COD, TKN and TP removal rate of 7.48, 82.5 and 0.63 mg/L/min respectively. The COD removal was achieved by direct interaction MW and UV with organics. The photocatalytic oxidation of NH3 to nitrite and nitrate at catalyst surface cause TKN removal from SDIW. On the other hand, major route of TP removal was phosphate reduction occurred in the aqueous phase. On the other hand, the desorption study performed with the catalyst used in the MWPC experiments indicated a TP concentration <2 mg/L and COD and TKN concentrations <5 mg/L indicating the complete removal of organic matter, TKN and TP from aqueous and solid phase during the MWPC process.

CO2 bio-fixation and biofuel production in an airlift photobioreactor by an isolated strain of microalgae Coelastrum sp. SM under high CO2 concentrations.

Microalgae cultivation is a promising approach to remove ambient CO2 via photosynthesis process. This paper investigates the impact of high CO2 concentrations (6, 12, and 16%) on algae growth, CO2 biofixation, lipid and carbohydrate contents, and nutrient removal of newly isolated microalgae, Coelastrum sp. SM. In addition, the ability of microalgae to produce biodiesel at optimal condition was studied. The microalgae were cultivated in wastewater using an airlift photobioreactor. Under 12% CO2, the maximum biomass productivity and CO2 fixation rate were 0.267gL-1day-1 and 0.302gL-1h-1, respectively. Total Kjeldahl nitrogen (TKN), total phosphorous (TP), nitrate, and sCOD removal efficiency were 84.01, 100, 86.811, and 73.084%, respectively. Under 12% CO2 and at the same condition for cell growth, the highest lipid and carbohydrate contents were 3 7.91 and 58.45%, respectively. The composition of fatty acids methyl ester (FAME) of the microalga lipid was defined. Based on the obtained results and FAME profile, Coelastrum sp. SM was a suitable feedstock for biodiesel production and also, the organism had a great potential for CO2 biofixation, which is also more suitable than any other reported strains in other related studies.

Performance of the first stage of the French system of vertical flow constructed wetlands with only two units in parallel: influence of pulse time and instantaneous hydraulic loading rate.

The technology of vertical flow constructed wetlands - French system for treating raw wastewater depends on several hydraulic factors, one of them being the duration of the pulse feeding and the resulting instantaneous hydraulic loading rate. This paper analyses two scenarios in the same system, the first of a faster feeding by pump and the second of a slower feeding by siphon, both with instantaneous hydraulic loading rate values lower than the literature recommendations. The system treated raw wastewater from a population equivalent of 100 p.e. in Brazil, and was comprised by only the first stage and two units in parallel. The shorter duration of feeding time and higher instantaneous hydraulic loading rate were associated with significantly higher chemical oxygen demand and total Kjeldahl nitrogen removal efficiencies, but with no significant differences in terms of biochemical oxygen demand (BOD) and suspended solids (SS). Oxygen concentrations and redox potential in the effluent were evaluated, together with the effluent flow rate profiles. The removal efficiencies were associated with the accumulation of solids in the upper part of the filter resulting from seven years of operation and to the operating hydraulic conditions, which are important elements in the performance of the system.

Resilience and reliability of compact vertical-flow treatment wetlands designed for tropical climates

Most of the tropical areas have sanitation problems to contend with. The French system of vertical-flow treatment wetlands (FS-VFTW) fed with raw wastewater could be a good water and sludge management solution. The purpose-adapted tropical design can reduce area requirement to below 1 m2/population equivalents (p.e.). The Taupinière FS-VFTW on Martinique Island was built according to this design, with one stage but with a saturated layer at the bottom of the filter and a simplified trickling filter (TF) added for further treatment to meet the high performances targeted. Unsaturated/saturated vertical-flow filters (US/S FS-VFTW) have shown improved performances on total nitrogen, carbon and suspended solids removal in temperate climates, but the performances in tropical conditions remain unknown.Here, we report on real-world-operation in the French Overseas Territories (FOT), the reliability and performances of this VFCW tropical-design. The system experienced loading conditions ranging from 30% to 165% of nominal carbonaceous biological oxygen demand (BOD5), as well as tropical rainstorms that brought over 7 times the nominal hydraulic load. Over a period of 3 years, 29 campaigns collected 24-h flow-proportional samples at each treatment stage (raw wastewater, FS-VFTW outlet, TF outlet). When applied loads were close to nominal values, the US/S FS-VFTW itself guarantees 85/90/60/50% removal and 125/25/40/50 mg/L at the outlet for chemical oxygen demand (COD)/total suspended solids (TSS)/total Kjeldahl nitrogen (TKN)/total nitrogen (TN), respectively. By comparison with US/S systems in mainland France, it appears that the warmer tropical-climate temperatures facilitate both nitrification and denitrification kinetics.Performances in overload conditions confirm that the US/S FS-VFTW remains robust and reliable although COD and TKN removal are impacted, especially after strong tropical rain events. By adding a simple compact trickling filter to a US/S FS-VFTW, the treatment system delivers high-level performances (>95% removal for BOD5, COD, TSS and TKN) at less than 1 m2/p.e.

LAB-SCALE STUDY ON CO-DIGESTION OF KITCHEN WASTE, SLUDGE AND SEWAGE

Anaerobic digestion is widely used for biodegradable solid organic wastes in order to recover bio-energy in the form of biogas. Some previous studies presented that co-digestion of various substrates can improve biogas yields as well as enhanceperformance of organic wastes digestion, in comparison with digestion of sole solid waste. This study aimed to evaluate the performance of anaerobic mono-digestion and anaerobic co-digestion of the following mixtures: (a) sole kitchen waste (KW), (b) KW and sewage (SW), (c) sole sludge (SL)and (d) KW and SL. This study was conductedby four lab-scale anaerobic complete mixing reactors (numbered MH1 – MH4) in 4,5 liters working volume atorganic loading rate (OLR) 2,0 g(VS).L-1.d-1. The KW was collected from canteen B4 and SW was collected from effluent from septic tank C6 Building in Ho Chi Minh University of Technology (HCMUT). The results show that the reactor of sole KW obtained average total chemical oxygen demand (tCOD), soluble chemical oxygen demand (sCOD), total solid (TS), volatile solid (VS), total phosphorus (TP) and total Kjeldahl nitrogen (TKN) of 62 %, 62 %, 71 %, 72 %, 73 % and 45 %, respectively, whereas reactor of KW and SW co-digestion had were tCOD, sCOD, TS, VS, TP and TKN removal of 73 %, 78 %, 75 %, 79 %, 59 % and 57 %, respectively. Thus co-digestion of KW and SW revealed an efficient enhancement of digestion, instead of sole KW digestion. Similarly, TS (74 %) and VS removals (75 %) of co-digesting mixtures of SL and KW were higher than those of sole SL digestion (67 %). Furthermore, co-digestion of SL and KW obtained better performance in tCOD and sCOD removals (70 % and 76 %, respectively).