Stable Effluent Quality Research Articles

Application of a water-energy-carbon coupling index to evaluate the long-term operational stability of the anaerobic-anoxic-oxic-membrane bioreactor (A2/O-MBR) process under the influence of rainstorms

In the context of global climate change, sudden rainstorms and typhoons induce fluctuations in hydraulic shocks to wastewater treatment plants (WWTPs) in coastal areas, causing two challenges of stable effluent quality and low-carbon operation. We established a quantitative evaluation method for resistance of wastewater treatment processes to hydraulic shocks based on the water-energy-carbon nexus using operational data from a WWTP in southeast coastal China from July 2018 to December 2022. The effects of hydraulic shocks on the operational stability of the anaerobic-anoxic-oxic-membrane bioreactor (A2/O-MBR) process were analyzed following five steps. The results showed that the gray water footprint (GWF) of the process was 9.3% lower than that of the A2/O process. The energy footprint (ENF) and carbon footprint (CF) were approximately 2.1 times and 1.7 times higher than those of the A2/O process, respectively. The resistance to hydraulic shocks of the A2/O-MBR process is approximately 5.5 times higher than that of the A2/O process. In conclusion, the A2/O-MBR process exhibits higher process operational stability when subjected to hydraulic shocks, which is more conducive to the efficient and stable operation of WWTPs in rainstorm and typhoon-prone areas. The evaluation methodology provides qualitative technical support for selecting upgrading processes for WWTPs in different regions.

Performance of a Double-Filter-Medium Tandem Membrane Bioreactor with Low Operating Costs in Domestic Wastewater Treatment

To reduce the operating costs of conventional membrane bioreactors (MBRs) and improve the stability and quality of the dynamic membrane bioreactor (DMBR) effluent, a homemade inexpensive filter cloth assembly was connected to an up-flow ultra-lightweight-medium filter (UUF) in lieu of expensive membrane modules to form a double-filter-medium tandem (DT)-MBR. DT-MBR was used to treat domestic wastewater, and its removal efficiencies for chemical oxygen demand, ammonia nitrogen, total nitrogen, and total phosphorus were similar to those of aerobic MBR, with average removal rates of 91.1%, 98.4%, 15.1%, and 50.7%, respectively. The average suspended solid (SS) of the final effluent was 5.6 mg∙L−1, and the filter cloth assembly played a leading role in SS removal, with an average removal rate of 86.0% and a relatively stable removal effect with little impact via backwashing. The activated sludge zeta potential, flocculation and sedimentation properties, particle size distribution, microbial compositions, extracellular polymeric substances (EPS), and filtration resistance of the cake layer were analyzed; it was found that the cake layer, which can also be called the dynamic membrane (DM), had an excellent filtration performance. However, the DM theory could not reasonably explain why the effluent quality of the filter cloth assembly maintained good stability even after backwashing. The real reason must be related to the sieving of cloth pores. Therefore, the concept of an in situ autogenous static membrane (ISASM) was proposed. With low operating costs and good and stable effluent quality, DT-MBR is a desirable alternative to the traditional MBR.

Biological pretreatment coupled gravity-driven membrane filtration for purifying decentralized domestic wastewater toward resource reuse

Membrane bioreactor (MBR) is an effective technology for the decentralized wastewater treatment; however, its high energy consumption and complex operation & maintenance limit its intensive application. This study introduced an innovative membrane-based process, gravity-driven membrane (GDM) filtration, to treat the decentralized wastewater without any cleaning procedures, and different biological pretreatments were constructed, including (I) tubular filler (TF-8), (II) tubular filler (TF-4), (III) fiber bundle filler (FBF), and (IV) sole aeration (control) to improve the filtration performance. The results indicated that the flux of GDM control can be maintained during long-term filtration in treating the real decentralized wastewater, and introducing the biological pretreatment processes could improve the stabilized flux of GDM without any influence on its stability. The average flux of TF-8/GDM was 3.69 ± 0.89 L m−2 h−1 during long-term filtration. Furthermore, coupling pre-treatment to GDM can effectively improve permeability quality and withstand the shock of water quality fluctuations. The average removal rates of chemical oxygen demand (COD) and dissolved organic carbon (DOC) by TF-8 were 59.7% and 48.3%, respectively. Besides, the organic contaminants could be further removed by the following GDM process owing to the biodegradation function of the self-formed biofilm on the membrane surface, and the DOC concentration in the GDM effluent can be reduced to as low as 4.5 mg L−1. Additionally, the elements of nitrogen (N) and phosphorus (P) could be effectively retention through the coupling process, with a retention rate of 84.3%–94.6% for total nitrogen (TN) and 99.8%–104.8% for total phosphorus (TP), respectively. Therefore, these findings can benefit to develop of new strategies to provide stable effluent quality, resource recovery, and energy consumption reduction in the membrane-based decentralized domestic wastewater treatment.

Activated Carbon Assisted Fenton-like Treatment of Wastewater Containing Acid Red G

The Fenton reaction as an effective advanced oxidation technology has been widely used in wastewater treatment for its stable effluent quality, simple operation, mild condition, and higher organic degradation with non-selectivity. However, the traditional Fenton reaction is limited by the sluggish regeneration of Fe2+, resulting in a slower reaction rate, and it is necessary to further increase the dosage of Fe2+, which will increase the production of iron sludge. Activated carbon (AC) has a strong adsorption property, and it cannot be ignored that it also can reduce Fe3+. In this study, the degradation of acid red G (ARG) by adding AC to the Fe3+/H2O2 system, the role of the reducing ability, and the reason why AC can reduce Fe3+ were studied. By adding three kinds of ACs, including coconut shell-activated carbon (CSPAC), wood-activated carbon (WPAC), and coal-activated carbon (CPAC), the ability of ACs to assist the Fe3+/H2O2 Fenton-like system to degrade ARG was clarified. Through the final treatment effect and the ability to reduce Fe3+, the type of AC with the best promotion effect was CSPAC. The different influence factors of particle size, the concentration of CSPAC, concentration of H2O2, concentration of Fe3+, and pH value were further observed. The best reaction conditions were determined as CSPAC powder with a particle size of 75 μm and dosage of 0.6 g/L, initial H2O2 concentration of 0.4 mmol/L, Fe3+ concentration of 0.1 mmol/L, and pH = 3. By reducing the adsorption effect of CSPAC, it was further observed that CSPAC could accelerate the early reaction rate of the degradation process of ARG by the Fe3+/H2O2 system. FT-IR and XPS confirmed that the C-O-H group on the surface of CSPAC could reduce Fe3+ to Fe2+. This study can improve the understanding and role of AC in the Fenton reaction, and further promote the application of the Fenton reaction in sewage treatment.

Process characteristics and energy self-sufficient operation of a low-fouling anaerobic dynamic membrane bioreactor for up-concentrated municipal wastewater treatment

Up-concentration of municipal wastewater using physico-chemical methods can effectively enrich organic matter, facilitating subsequent anaerobic digestion of up-concentrated wastewater for enhanced methanogenesis at reduced energy consumption. An anaerobic dynamic membrane bioreactor (AnDMBR) assisted with biogas-sparging was developed to treat up-concentrated municipal wastewater, focusing on the effects of operating temperature and hydraulic retention time (HRT) as well as COD mass balance and energy balance. The COD removal stabilized at about 98 % over the experimental period, while gaseous and dissolved methane contributed 43–49 % and 2–3 % to the influent COD reducing greenhouse gas emissions. The formed dynamic membrane exists mainly as a heterogeneous cake layer with a uneven distribution feature, ensuring the stable effluent quality. Without adopting any physico-chemical cleaning, the transmembrane pressure (TMP) maintained at a low range (2.7 to 14.67 kPa) with the average TMP increasing rate of 0.089 kPa/d showing a long-term low-fouling operation. Increasing the concentration ratio, the methane production rate decreased from 0.18 to 0.15 L CH4/gCOD likely due to the accumulation of particulate organics. Microbial community analysis indicated the predominant methanogenic pathway shifted from hydrogenotrophic to acetoclastic methanogenesis in response to the temperature change. Net energy balance (0.003–0.600 kWh/m3) can be achieved only under room temperature (25 °C) rather than mesophilic conditions (36 °C).

Dynamic membranes with sparse nanofibers as the skeletons yield better and more stable effluent quality without sacrificing the flux in bioreactors

Previous studies found that the inhabitation of filamentous bacteria on the support materials with large apertures in dynamic membrane bioreactor (DMBR) could stabilize the DM structure and resulted in stable effluent quality. However, it is hard to cultivate the filamentous bacteria on support materials in DMBR intentionally. In present study, a polyvinyl alcohol (PVA) nanofiber layer was coated on 180-μm nylon mesh to simulate the inhabitation of filamentous bacteria. The nanofiber coated mesh with 1 h spinning time (referred as PVA-1h) had a similar porosity (14.9%) to that of 25-μm nylon mesh and dominant pore size of 1.0–2.5 μm. Short-term test indicated that the PVA-1h had a low initial effluent turbidity of 5.3 NTU and could form DM within 5 min. Long-term test in DMBR demonstrated that better and more stable effluent quality (0.71 ± 0.31 NTU) was achieved by PVA-1h compared to typical used support materials of 25-μm mesh (1.04 ± 0.60 NTU). However, the PVA-1h had an operation flux of 30–50 L/(m2·h) with a water head loss ≤2 cm, which was comparable with the 25-μm mesh but much greater than that of 2.6-μm mesh (<5 L/(m2·h)). In addition, the filtration resistance change between the PVA-1h and 25-μm mesh were very similar. Therefore, this study demonstrated that with proper density of nanofiber as the skeletons, DMs would be formed more quickly and stably, resulting in better and more stable effluent quality in DMBR without sacrificing operation flux.

Impact of organics, aeration and flocs on N2O emissions during granular-based partial nitritation-anammox

Partial nitration-anammox is a resource-efficient technology for nitrogen removal from wastewater. However, the advantages of this nitrogen removal technology are challenged by the emission of N2O, a potent greenhouse gas. In this study, a granular sludge one-stage partial nitritation-anammox reactor comprising granules and flocs was run for 337 days in the presence of influent organics to investigate its effect on N removal and N2O emissions. Besides, the effect of aeration control strategies and flocs removal was investigated as well. The interpretation of the experimental results was complemented with modelling and simulation. The presence of influent organics (1 g COD g-1 N) helped to suppress NOB and significantly reduced the overall N2O emissions while having no significant effect on anammox activity. Besides, long-term monitoring of the reactor indicated that constant airflow rate control resulted in more stable effluent quality and less N2O emissions than DO control. Still, floc removal reduced N2O emissions at DO control but increased N2O emissions at constant airflow rate. Furthermore, anammox bacteria could significantly reduce N2O production during heterotrophic denitrification, likely via competition for NO with heterotrophs. Overall, this study demonstrated that the presence of influent organics together with proper aeration control strategies and floc management could significantly reduce the N2O emissions without compromising nitrogen removal efficiency during one-stage partial nitritation-anammox processes.

Integrated Anaerobic-Aerobic and Wetland System for Wastewater Treatment and Recycling in Fish Canning Industry

Fish canning industry is one of the top priority industries in Indonesia that is competitive in international market and essential to food security. It is also an industry with high water consumption due to its water-intensive processes such as thawing and washing that produces large amount of wastewater containing very high load of organic pollutants which must be treated properly before disposal into the environment. This study was conducted using wastewater characteristics from one of the fish canning plants in Bali, Indonesia, that already implemented wastewater treatment using a combination of aerobic treatments with trickling filter and activated sludge. The treatment system has difficulty to achieve a good and stable effluent quality, especially during high load production season. It is necessary to find a better system that can treat the high load of organic content in wastewater and produce a cleaner effluent that can be recycled back into the production process. This study is aimed to develop a model of integrated system comprised of sedimentation, coagulation-flocculation, Upflow Anaerobic Sludge Blanket (UASB) and Modified Ludzack-Ettinger (MLE) that can be used as a base design for further implementation in pilot-scale facility. The integrated system was designed to remove 99 % of BOD, 99 % of oil and grease, 98 % of TSS and 87.8 % of total nitrogen achieving effluent quality of 59.9 mg/L BOD, 0.6 mg/L oil and grease, 27.4 mg/L TSS, and 30.0 mg/L total nitrogen in nitrates form. Compared to the existing treatment system with effluent quality of 351.4 mg/L BOD, 337 mg/L TSS and 111.1 mg/L ammonia, this system could improve the effluent quality significantly by maintaining a hydraulic retention time (HRT) of 55.3 h. Combining constructed wetland with HRT of 28.8 h as water reclamation system to refine the water quality, the nitrogen content could be reduced to less than 10 mg/L to meet the requirement as raw water for clean water production process. The design in this study could be used to replace the existing aerobic treatment system and enable the industry to solve the environmental problems of wastewater disposal and water conservation and expand further the production capacity simultaneously.

The influence of the outlet position and substrate on the nitrogen purification of vertical flow constructed wetlands

To investigate the influence of outlet location on nitrogen removal in Vertical Flow Wetlands (VFWS), three VFWS, that were, wetland H (planting Pennisetum Hydridum), wetland X (planting Pennisetum purpureum Schum.) and wetland CK (no planting) were constructed. High, medium and low water outlets were set in each wetland, namely A, B and C. The main results were as followed: TN (total nitrogen) removal efficiency of A, B, C in H wetland was 61.3%, 55.4%, 53.2 %, and variance analysis was 100.2, 137.1, 177.8. A, B, C in X wetland was 58.3%, 56.6%, 50.2%, and variance analysis was 55.6, 68.8, 116.4. A, B, C in CK wetland was 53.1%, 51.5%, 50.2%, and variance analysis was 131.9, 188.7, 275.4, respectively. The content of nitrogen and urease activity in the substrate decreased with increasing of substrate depth. These results indicated that planting Pennisetum Hydridum and Pennisetum purpureum Schum. In VFW and appropriately raising outlet position could help improve nitrogen removal efficiency and obtain relatively stable effluent quality, and the upper substrate (0-10 cm) was the main site for nitrogen interception and purification. It can provide theoretical basis for the scientific construction and management of VFW.

Application of MBR Technology in Schoolyard Domestic Sewage Treatment

This paper discusses the special features of campus sewage, and chooses more suitable sewage treatment for campus sewage. At the same time, it expounds the advantages and disadvantages of it. Compared with city sewage from industry and agriculture, campus sewage has much more characteristic content of pollutants with higher COD, SS and tiny toxic pollutants[5]. Therefore rather than using the traditional activated sludge process, MBR is more appropriate for schoolyard domestic sewage treatment for small area, stable effluent quality, good removal efficiency and little residual sludge production. Additionally, new campuses of universities are always built far away from the city centre, and the water transportation cost can be saved with a sewage treatment system in the campus. The treated water has the quality to be used as gray water for campus watering, cleaning and so on, which can also help the universities to save money. Undeniably, it also has the disadvantages of high energy consumption and cost, for it needs to update the active membrane regularly. If it is used in cities, it will be a huge financial burden for governments. But when it is used in campuses, less sewage will need less membranes, and the polluted membranes can also be used for students’ research.

Plant diversity improves the effluent quality and stability of floating constructed wetlands under increased ammonium/nitrate ratio in influent

The major targets of constructed wetlands (CWs) during wastewater treatment include achieving high-quality effluent and maintaining stable effluent quality. Plant species diversity can increase nitrogen (N) removal efficiency and improve effluent quality by decreasing the effluent N concentrations, including nitrate (NO3−-N), ammonium (NH4+-N) and total inorganic nitrogen (TIN) concentrations in CWs. However, the effect of plant diversity on the stability of effluent quality in response to perturbation in the form of an increased NH4+/NO3− ratio in influent has not been studied. This study conducted a microcosm experiment and assembled four plant species richness levels (1, 2, 3 and 4) and 15 species compositions by using 90 simulated CW microcosms to investigate the effect of plant diversity on the effluent N concentrations and their stability with an increase in the influent NH4+/NO3− ratio from 0:100 to 33:67 in the later stage of the experiment. The results showed that (1) plant species richness maintained a positive effect on effluent quality under an increased influent NH4+/NO3− ratio; (2) high species richness enhanced the stability of effluent water quality; (3) the presence of Phragmites australis in the community decreased the effluent TIN concentration and improved its stability under perturbation; and (4) the presence of Typha latifolia had a positive effect on N removal efficiency under perturbation. The establishment of communities with high plant species richness and proper species (such as P. australis) could simultaneously improve the effluent quality and stability in CWs for treating wastewater with increased NH4+/NO3− ratio.

Implication of Non-electrostatic Contribution to Deionization in Flow-Electrode CDI: Case Study of Nitrate Removal From Contaminated Source Waters.

While flow-electrode capacitive deionization (FCDI) operated in short-circuited closed cycle (SCC) mode appears to hold promise for removal of salt from brackish source waters, there has been limited investigation on the removal of other water constituents such as nitrate, fluoride or bromide in combination with salt removal. Of particular concern is the effectiveness of FCDI when ions, such as nitrate, are recognized to non-electrostatically adsorb strongly to activated carbon particles thereby potentially rendering it difficult to regenerate these particles. In this study, SCC FCDI was used to desalt source waters containing nitrate at different concentrations. Results indicate that nitrate can be removed from source waters using FCDI to concentrations <1 mg NO3-N L−1 though a lower quality target such as 10 mg L−1 would be more cost-effective, particularly where the influent nitrate concentration is high (50 mg NO3-N L−1). Although studies of the fate of nitrate in the FCDI system show that physico-chemical adsorption of nitrate to the carbon initially plays a vital role in nitrate removal, the ongoing process of nitrate removal is not significantly affected by this phenomenon with this lack of effect most likely due to the continued formation of electrical double layers enabling capacitive nitrate removal. In contrast to conventional CDI systems, constant voltage mode is shown to be more favorable in maintaining stable effluent quality in SCC FCDI because the decrease in electrical potential that occurs in constant current operation leads to a reduction in the extent of salt removal from the brackish source waters. Through periodic replacement of the electrolyte at a water recovery of 91.4%, we show that the FCDI system can achieve a continuous desalting performance with the effluent NO3-N concentration below 1 mg NO3-N L−1 at low energy consumption (~0.5 kWh m−3) but high productivity.

Anaerobic Treatment of Wastewater in Colder Climates Using UASB Reactor and Anaerobic Membrane Bioreactor

Direct anaerobic treatment in the main line of a wastewater treatment plant is a promising way of recovering chemical energy, even in moderate climates. Full-scale applications of upflow anaerobic sludge blanket (UASB) reactors are common in warm climates and have recently begun to appear in areas with colder climate. Several new types of reactors optimized for low temperature treatment were proposed such as UASB-Digester or anaerobic membrane bioreactor (AnMBR). However, long-term operation of such systems treating real wastewater at winter temperatures is needed to assess their suitability. The aim of this article is to evaluate the operation of a laboratory-scale UASB reactor (1.9 L) before and after the installation of ultrafiltration membrane for solids separation from the effluent. The laboratory model treated wastewater at 15°C for over 850 days. The organic loading rate of the UASB reactor and AnMBR was 1.4 and 1.6 g COD/[L·d], respectively, while the hydraulic retention time was around 9 and 10 h. Energy recovery from the wastewater in gaseous methane was 4% and 6% in the UASB reactor and AnMBR, respectively. The methane content was 63% ± 17% and 64% ± 2%, respectively. In the UASB reactor, 64% of the influent chemical oxygen demand (COD) was removed in long term. The AnMBR ran at average 85% COD removal. Results show that AnMBR can deliver more stable effluent quality for wastewater treatment even at low (15°C) temperature. However, even the AnMBR effluent requires further posttreatment. Thus, simpler and less energy demanding UASB appears more relevant for wastewater pretreatment under European conditions.

Real-time optical monitoring of the wastewater treatment process

One activated sludge process line was optically monitored in situ by a novel image analysis equipment. The results of the image analysis were studied to find out dependencies to the process variables of the wastewater treatment plant (WWTP) and to the quality of the treated wastewater. The quality parameter of the treated wastewater, suspended solids, was modelled using the image analysis results. The model can be used for evaluating the performance of the WWTP and for the better control for stable effluent quality. It was shown that the results of the online optical monitoring reveal useful information from the process and can be used in forecasting the quality of biologically treated wastewater. The optical monitoring method together with process measurements has an important role in keeping the process in stable operating conditions and avoiding environmental risks.

하수처리장의 포기조 최적 DO 농도 산정 및 공기송풍량 자동제어를 통한 에너지 절감 효과 도출

생물학적 하수처리공정에서 안정적인 방류수질 확보와 처리 비용을 적게 하는 것은 매우 중요하다. 하지만 유입수 유량 및 성분 농도의 변화와 미생물의 비선형적인 동특성, 기타 환경 요인에 의해서 최적의 운전 제어를 하기가 쉽지 않기 때문에, 기존의 하수처리장에서는 필요한 양 이상의 폭기 및 화학물질을 과량 주입하는 방법 등을 사용하였다. 본 연구에서는 포기조에서 미생물에 필요한 용존산 소농도를 유지함과 동시에 과폭기로 인한 전력 비용을 감소할 수 있는 최적 제어 방법을 제안하였다. 최적 제어를 위하여 실시간 미생물 호흡률 측정기(Oxygen uptake rate, OUR)을 이용하여 측정하였고, 실시간 호흡률 측정값을 바탕으로 현재 미생물에 필요한 최적 DO 농도를 제안하였으며, 이에 따라 공기송풍기가 자동제어될 수 있도록 구성하였다. 최적 제어 방법을 통하여 하수처리장 포기조의 공기 송풍량에 소요되는 전력비용을 절감할 수 있었다. It is important to keep stable effluent water quality and minimize operation cost in biological wastewater treatment plant. However, the optimal operation is difficult because of the change of influent flow rate and concentrations, the nonlinear dynamics of microbiology growth rate and other environmental factors. Therefore, many wastewater treatment plants are operated for much more redundant oxygen or chemical dosing than the necessary. In this study, the optimal control scheme for dissolved oxygen (DO) is suggested to prevent over-aeration and the reduction of the electric cost in plant operation while maintaining the dissolved oxygen (DO) concentration for the metabolism of microorganisms in oxic reactor. For optimal control, The oxygen uptake rate (OUR) is realtime measured for the identification of influent characterization and the identification of microorganisms' oxygen requirement in oxic reactor. Optimal DO seT-Point needed for the microorganism is suggested based on real time measurement of oxygen uptake of microorganism and the control of air blower. Therefore, both stable effluent quality and minimization of electric cost are satisfied with a suggested optimal setpoint decision system by providing the necessary oxygen supply requirement to the microorganisms coping with the variations of influent loading.

Modeling the dioxin emission of a municipal solid waste incinerator using neural networks

Incineration is considered as an efficient approach in dealing with the increasing demand for municipal and industrial solid waste treatment, especially in areas without sufficient land resources. Facing the concern of health risk, the toxic pollutants emitted from incinerators have attracted much attention from environmentalists, even though this technology is capable of reducing solid waste volume and demand for landfill areas, together with plenty of energy generation. To reduce the negative impacts of toxic chemicals emitted from incinerators, various monitoring and control plans are made not only for use in facilities performance evaluation but also better control of operation for stable effluent quality. How to screen out the key variables from massive observed and control variables for modeling the dioxin emission has become an important issue in incinerator operation and pollution prevention. For these reasons, this study used 4-year monitoring data of an incinerator in Taiwan as a case study, and developed a prediction model based on an artificial neural network (ANN) to forecast the dioxin emission. By doing this, a simplified monitoring strategy for incinerators with regarding to dioxin emission control can be achieved. The result indicated that the prediction model based on a back-propagation neural network is a promising method to deal with complex and non-linear data with the help of statistics in screening out the useful variables for modeling. The suitable architecture of an ANN for using in the dioxin prediction consists of 5 input factors, 3 basic layers with 8 hidden nodes. The R2 was found to equal 0.99 in both the training and testing steps. In addition, sensitivity analysis can identify the most significant variables for the dioxin emission. From the obtained results, the frequency of activated carbon injection showed as the factor of highest relative importance for the dioxin emission.

The Experimental Study on Landfill Leachate Treatment by Coagulation-Sedimentation + Electro-Oxidation Joint Reactor

The technology used the coagulation-sedimentation + electro-oxidation joint reactor has been studied to treat landfill leachate. First adding FeCl30.4g/L into all leachate for coagulation and sedimentation, its CODcr elimination rate can achieve 35%, but does have no effect on ammonia nitrogen. Then using electro-oxidation reactor to deal with effluent water, the reaction order of electro-oxidation reactor is first-level, as the reaction conditions are 20mA/cm2 of electric current density, 140min of reaction time, the leachate CODcr elimination rate can reach to above 90%, the ammonia nitrogen elimination rate meets to 98% around. Using coagulation-sedimentation + electro coagulation joint reactor to treat landfill leachate can get stable effluent water quality with good treatment effect, has very high elimination efficiency of CODcr and ammonia nitrogen. It is a suitable treatment technology for landfill leachate.

Biotreatment of Industrial Wastewaters under Transient-State Conditions: Process Stability with Fluctuations of Organic Load, Substrates, Toxicants, and Environmental Parameters

Biotreatment of industrial wastewater is often challenged by operation under transient states with respect to organic loads, pollutants, and physical characteristics. Furthermore, the potential presence of inhibitory compounds requires careful monitoring and adequate process design. This review describes difficulties encountered in biological treatment of wastewater with highly variable influent characteristics. Typical design aspects of biological processes are presented and discussed with respect to their success in treating highly fluctuating wastewaters. In general, biomass retention is a key factor for dealing with highly fluctuating and/or inhibitory wastewater, but the how it operates also affects the stability of performance, as it was shown that dynamic operation instead of operation at a constant flow enhances biodegradation onset and more evenly distributed activity. Although ultimately stable effluent quality must be achieved, the microbial population stability is not necessarily high, as it was shown that microbial diversity and flexibility may play a critical role in functional stability.

Glycosphingolipids as a Possible Signature of Microbial Communities in Activated Sludge and the Potential Contribution of Fungi to Wastewater Treatment under Cold Conditions

Seven strains of fungi were isolated from activated sludge and identified as Mucor sp., Geotrichum sp., Trichosporon sp., Candida sp., and Trichoderma sp. by 28S rDNA D2 region sequences analysis. The structures of the main ceramide monosaccharides (CMSs) from these fungi were identified as glucosylceramide (GlcCer) consisting of ceramide moieties of 9-methyl-octadeca-sphingadienine (9-Me d18:2), with 2-hydroxyhexadecanoate (h16:0) (Mucor sp. and Geotrichum sp.), 2-hydroxyoctadecanoate (h18:0) (Trichosporon sp. and Candida sp.), and 2-hydroxyoctadecenoate (h18:1) (Trichoderma sp.). Seasonal changes in glycosphingolipids in activated sludge suggest the possibility that microbial flora in activated sludge changes with the seasons, and that fungi adaptable to low temperatures dominate in the cold period, resulting in the maintenance of stable effluent quality. Mucor sp., Geotrichum sp., and Candida sp. satisfactorily reduced the BOD of synthetic sewage at 10 degrees C. These results indicate that fungi in activated sludge can contribute to wastewater treatment in cold conditions.

A high filtration system with synthetic permeable media for wastewater reclamation

A novel filtration process with synthetic permeable media was investigated for secondary effluent reclamation. Polyurethane was chosen as the filter medium among three tested media. Compressibility and up-flow velocity were changed to determine the optimum operation for the system. An equation was introduced to express the relationship between the removal efficiency and up-flow velocity. In a pilot study, the synthetic medium filtration with compression showed very stable effluent quality without clogging trouble, though the system operated with three times higher filtration rate and much longer backwashing interval than conventional systems.