A novel sulfate reduction, autotrophic denitrification, nitrification integrated (SANI) process for saline wastewater treatment

This paper reports on a lab-scale evaluation of a novel and integrated biological nitrogen removal process: the sulfate reduction, autotrophic denitrification and nitrification integrated (SANI) process that was recently proposed for saline sewage treatment. The process consisted of an up-flow anaerobic sludge bed (UASB) for sulfate reduction, an anoxic filter for autotrophic denitrification and an aerobic filter for nitrification. The experiments were conducted to evaluate the performance of the lab-scale SANI system with synthetic saline wastewater at various hydraulic retention times, nitrate concentrations, dissolved oxygen levels and recirculation ratios for over 500 days. The system successfully demonstrated 95% chemical oxygen demand (COD) and 74% nitrogen removal efficiency without excess sludge withdrawal throughout the 500 days of operation. The organic removal efficiency was dependent on the hydraulic retention time, up-flow velocity, and mixing conditions in the UASB. Maintaining a sufficient mixing condition in the UASB is important for achieving effective sulfate reduction. For a typical Hong Kong wastewater composition 80% of COD can be removed through sulfate reduction. A minimum sulfide sulfur to nitrate nitrogen ratio of 1.6 in the influent of the anoxic filter is necessary for achieving over 90% nitrate removal through autotrophic denitrifiers which forms the major contribution to the total nitrogen removal in the SANI system. Sulfur balance analyses confirmed that accumulation of elementary sulfur and loss of hydrogen sulfide in the system were negligible.     

进水N/S值对同步脱硫反硝化特性的影响

研究了不同进水N/S值条件下,不同接种物的厌氧体系的同步脱硫反硝化特性。结果表明:在N/S为0.6或0.4的条件下,3个体系对硫化物的去除率均达到90%以上,其中以进水N/S为0.4时产生的悬浮态硫最多;硝态氮的去除特性与硫化物不同,3个体系对硝态氮的去除率均在进水N/S为1.0时达到100%,且此时N2的产量也最大。可见,尽管同步脱硫反硝化工艺具备同时脱氮及除硫的能力,但其进水N/S的控制值却不相同。对于脱硫而言,最佳的进水N/S为0.4;对于脱氮而言,最佳的进水N/S为1.0。此外,研究发现3个不同接种物的厌氧体系对硫化物及硝态氮的去除途径不同,进水N/S值的影响也有差异。对于接种了厌氧污泥的体系,存在自养反硝化和异养反硝化的竞争,改变进水N/S值可调节二者的竞争,高N/S值会抑制硫化物自养反硝化过程,降低对硫化物的去除率;对于接种脱氮硫杆菌的纯菌体系,多硫自催化反应会与硫化物自养反硝化反应竞争硫化物,降低对硝态氮的去除率,高N/S值会导致出水硝态氮浓度较高;对于添加脱氮硫杆菌的强化厌氧污泥体系,以硫化物自养反硝化过程为主,最佳的N/S为0.4。     

Engineered ecosystem for sustainable on-site wastewater treatment

A pilot-scale engineered ecosystem (PSEE) operated for over 2 years in sub-tropical conditions, produced an effluent with COD (median 38 mg/L) and TSS (median 3mg/L) levels comparable to that required by the AS/NZS 1547:2000 Onsite Domestic Wastewater Management standard. Only partial nitrification was achieved as dissimilatory nitrate reduction to ammonia occurred; however the level of NH(4)-N was reduced by 75% and total inorganic nitrogen by 53%. Phosphorus was not removed by the system due to the lack of regular sludge removal. Mass balances around the system showed that bacteria removed 36% of the influent nitrogen and 76% of the influent COD. Algae and plants were shown to remove 5% of the influent nitrogen, and 6% of the influent phosphorus. Challenges in developing a sustainable on-site wastewater treatment system were largely met by minimising chemical, energy and labour inputs, eliminating the need for frequent sludge handling, and creating an effluent quality suitable for re-use in non-potable applications. However, the sludge removal from the system needs to be adequately managed to avoid excessive accumulation as this can cause a range of negative impacts.     

UBAF/化学除磷处理宾馆污水并回用

济南南郊宾馆的排水量及杂用水量均较大,为此采用水解—上向流曝气生物滤池(UBAF)—纤维过滤器(加药除磷)工艺处理宾馆污水,通过将UBAF的滤层分成缺氧区和好氧区,使UBAF具有了碳化、硝化与反硝化的功能,其对氨氮的去除率>85%,对COD的去除率在80%左右,在回流比为50%的条件下对总氮的去除率约30%。UBAF出水投加硫酸铝后进行纤维过滤除磷,在投量为20mg/mgTP的条件下可确保出水TP<1mg/L。     

Sulfide-induced nitrate reduction in the sludge of an anaerobic digester of a zero-discharge recirculating mariculture system

The anaerobic digester is a vital component in a zero-discharge mariculture system as therein most of the organic matter is mineralized and nitrogen-containing compounds are converted to gaseous N₂. Although denitrification is a major respiratory process in this nitrate-rich treatment stage, also sulfate respiration takes place and may cause undesirable high sulfide concentrations in the effluent water. To examine the effect of sulfide on nitrate reduction, in situ depth profiles of inorganic nitrogen and sulfur compounds were determined. Additionally, nitrate reduction was examined as a function of ambient sulfide concentrations in sludge collected from different locations in the anaerobic reactor. Depth profiles showed high concentrations of nitrate and low concentrations of sulfide and ammonia in the aqueous layer of the reactor. A sharp decrease of nitrate and an increase in sulfide and ammonia concentrations was measured at the water-sludge interface. Nitrate reduction was highest in this interface zone with rates of up to 8.05 ± 0.57 μmol NO₃⁻ h⁻¹ g_(sludge)⁻¹. Addition of sulfide increased the nitrate reduction rate at all sludge depths, pointing to the important role of autotrophic denitrification in the anaerobic reactor. Dissimilatory nitrate reduction to ammonia (DNRA) was found to be low in all sludge layers but was enhanced when sludge was incubated at high sulfide concentrations. Although nitrate reduction rates increased as a result of sulfide addition to sludge samples, no differences in nitrate reduction rates were observed between the samples incubated with different initial sulfide concentrations. This as opposed to sulfide oxidation rates, which followed Michaelis-Menten enzymatic kinetics. Partial oxidation of sulfide to elemental sulfur instead of a complete oxidation to sulfate, could explain the observed patterns of nitrate reduction and sulfide oxidation in sludge incubated with different initial sulfide concentrations.     

污泥减量工艺:HA-A/A-MCO的好氧脱氮机制分析

针对污泥减量技术存在对氮、磷去除能力低的问题,开发了一种具有强化脱氮除磷功能并可实现污泥减量化的HA-A/A-MCO工艺。在该工艺取得同步脱氮除磷和污泥减量优异效果的条件下,采用其处理校园生活污水,当进水TN平均为47 mg/L时,出水TN为10.9 mg/L,系统的总脱氮率为76.8%,其中好氧脱氮量占总脱氮量的50%,缺氧脱氮量占26%;HA-A/A-MCO系统存在着在好氧条件下具有反硝化能力的菌属,对好氧脱氮有一定贡献,且DO浓度对其反硝化能力没有抑制作用;好氧池中的DO浓度梯度有利于在污泥絮体内形成缺氧环境,从而促进同步硝化反硝化(SND)的发生,但减小污泥絮体尺寸会削弱絮体内部缺氧区域比例、降低SND的脱氮效率。     

SMSBR去除焦化废水中有机物及氮的特性

选用一体化膜—序批式生物反应器 (SubmergedMembraneSequencingBatchReac tor ,简称SMSBR)处理焦化废水 ,考察了能否通过膜分离的强化作用提高生物处理系统对焦化废水的处理效果 ,使出水COD达到新的排放标准 ( <10 0mg/L) ,并提高脱氮效率。研究结果表明 :在HRT为 32 .7h ,平均COD容积负荷为 0 .4 5kg/ (m3·d)的条件下 ,出水COD可以稳定在 10 0mg/L以下 (平均为 86.4mg/L) ;要使COD达到新的排放标准 ,进水COD容积负荷应低于 0 .67kg/ (m3·d) (该负荷下出水COD在 10 0mg/L上下波动 ,平均为 10 6.3mg/L) ;好氧段存在明显的反硝化现象 ,使COD的去除得到强化 ;在保证系统温度、碱度、溶解氧和不受进水COD负荷冲击的情况下 ,出水NH3-N可低于 1mg/L ,但泥龄太长所产生的微生物代谢产物抑制了硝化反应过程中的硝酸盐细菌 ,使好氧段出水NO2 -N/NOx-N平均为 91.1% ,因此系统获得极其稳定高效的短程硝化作用 ,有利于进一步脱氮 ;按“缺氧 1—好氧—缺氧 2”方式运行时 ,若“缺氧 2”的HRT>8.4 4h ,可实现 81.34 %的反硝化率 (外加碳源 :COD/N为 2 .1g/g) ,平均TN去除率为 87.2 % ,最高达 90 .2 %。     

Simultaneous heterotrophic and sulfur-oxidizing autotrophic denitrification process for drinking water treatment: control of sulfate production

A long-term performance of a packed-bed bioreactor containing sulfur and limestone was evaluated for the denitrification of drinking water. Autotrophic denitrification rate was limited by the slow dissolution rate of sulfur and limestone. Dissolution of limestone for alkalinity supplementation increased hardness due to release of Ca²⁺. Sulfate production is the main disadvantage of the sulfur autotrophic denitrification process. The effluent sulfate concentration was reduced to values below drinking water guidelines by stimulating the simultaneous heterotrophic and autotrophic denitrification with methanol supplementation. Complete removal of 75 mg/L NO₃-N with effluent sulfate concentration of around 225 mg/L was achieved when methanol was supplemented at methanol/NO₃-N ratio of 1.67 (mg/mg), which was much lower than the theoretical value of 2.47 for heterotrophic denitrification. Batch studies showed that sulfur-based autotrophic NO₂-N reduction rate was around three times lower than the reduction rate of NO₃-N, which led to NO₂-N accumulation at high loadings.     

Simultaneous methanogenesis and denitrification of pretreated effluents from a fish canning industry

A lab-scale hybrid upflow sludge bed-filter (USBF) reactor was employed to carry out methanogenesis and denitrification of the effluent from an anaerobic industrial reactor (EAIR) in a fish canning industry. The reactor was initially inoculated with methanogenic sludge and there were two different operational steps. During the first step (Step I: days 1-61), the methanogenic process was carried out at organic loading rates (OLR) of 1.0-1.25 g COD l-1 d-1 reaching COD removal percentages of 80%. During the second step (Step II: days 62-109) nitrate was added as KNO3 to the industrial effluent and the OLR was varied between 1.0 and 1.25 g COD l-1 d-1. Two different nitrogen loads of 0.10 and 0.22 g NO3(-)-N l-1 d-1 were applied and these led to nitrogen removal percentages of around 100% in both cases and COD removal percentages of around 80%. Carbon to nitrogen ratio (C:N) in the influent was maintained at 2.0 and eventually it was increased to 3.0, by means of glucose addition, to control the denitrification process. From these results it is possible to establish that wastewater produced in a fish canning industry can be used as a carbon source for denitrification and that denitrifying microorganisms were present in the initially methanogenic sludge. Biomass productions of 0.23 and 0.61 g VSS:g TOC fed for Steps I and II, respectively, were calculated from carbon global balances, showing an increase in biomass growth due to denitrification.     

硫自养波形潜流人工湿地的脱氮机理及工况优化

将硫自养反硝化工艺与潜流人工湿地相结合,考察了其对低碳氮比污水中氮的去除效果。结果表明,增加曝气装置后硫自养波形潜流人工湿地的脱氮效果可以得到保障,在气水比为8∶1、水力负荷为0.8 m³/(m²·d)时,TN去除率为(70±5)%,出水TN浓度低于8 mg/L;NH4+-N去除率在90%以上,出水NH4+-N浓度低于3 mg/L;COD去除率为(50±2)%,出水COD浓度低于40 mg/L;p H值可维持在7~9。同时,石灰石填料具有同步除磷的效果。该工艺具有脱氮效率高、效果好、运行费用低的特点。     

UASB/曝气沉淀/IC反应器处理高浓度硫酸盐有机废水

在赤霉素生产过程中产生的高浓度硫酸盐有机废水,处理难度较大。采用UASB／曝气沉影IC反应器工艺处理该废水,UASB中的硫酸盐还原菌将硫酸根还原为硫化物,曝气池中的脱硫杆菌则将硫化物氧化为单质硫,并在沉淀池中去除,IC反应器去除COD。系统稳定运行后,对硫酸盐的去除率〉90％,对COD的去除率〉80％。     

Organic removal by denitritation and methanogenesis and nitrogen removal by nitritation from landfill leachate

A system consisting of a two-stage UASB and anoxic-oxic reactor was used to enhance COD and nitrogen removal from landfill leachate. To improve denitrification efficiency, the raw leachate with recycled final effluent was pumped into the first-stage UASB (UASB1) to carry out simultaneous denitrification and methanogenesis. The results over 180 d show that the maximum organic removal rate in UASB1 and UASB2 was 12.5 and 8.5 kgCODm(-3)d(-1) in the oxic zone of the A/O reactor, respectively. The COD and biochemical oxygen demand (BOD5) removal efficiency of the system was 80-92% and about 99%, respectively. Without controlling temperature (17-30 degrees C) and dissolved oxygen (0.5-4.0 mgL(-1)), the maximum NH4+-N removal rate was 0.68 kg NH4+-Nm(-3)d(-1), and about 99% of NH4+-N removal was obtained by nearly complete nitritation. The 81-93% total nitrogen removal was obtained by complete denitrification in the UASB1 and in the anoxic zone of the A/O reactor. Fluorescence in situ hybridization (FISH) analysis of the sludge samples from A/O reactor showed that ammonia oxidizing bacteria (AOB) consisted 4% of the eubacterium, while nitrite oxidizing bacteria (NOB) counted less than 0.2% of that. The study shows that the main factors achieving and maintaining nitritation are a proper range of free ammonia concentration obtained by dilution recycled final effluent that inhibits NOB but not AOB; effective control on aeration time by indication of "ammonia valley" on pH profile; and highly efficient denitrification and its reproducing alkalinity to result in pH above 8.5.     

Innovative process scheme for removal of organic matter, phosphorus and nitrogen from pig manure

Disposal of pig manure often requires treatment with respect to environmental legislations. In this study different processes for reduction of the organic matter (anaerobic digestion, effluent separation by decanter centrifugation, membrane microfiltration, post-digestion in upflow anaerobic sludge blanket (UASB) reactor, partial oxidation), nitrogen (oxygen-limited autotrophic nitrification-denitrification, OLAND) and phosphorus (phosphorus removal by precipitation as struvite, PRS) from pig manure were tested. Results obtained showed that microfiltration was unsuitable for pig manure treatment. PRS treated effluent was negatively affecting the further processing of the pig manure in UASB, and was therefore not included in the final process flow scheme. In a final scheme (PIGMAN concept) combination of the following successive process steps was used: thermophilic anaerobic digestion with sequential separation by decanter centrifuge, post-digestion in UASB reactor, partial oxidation and finally OLAND process. This combination resulted in reduction of the total organic, nitrogen and phosphorus contents by 96%, 88%, and 81%, respectively.     

Combined bioelectrochemical and sulfur autotrophic denitrification for drinking water treatment

A combined bioelectrochemical and sulfur autotrophic denitrification process for drinking water treatment was put forward and investigated extensively in this paper. In this new process, the bioelectrochemical denitrification was carried out in the upper part of the reactor while sulfur denitrification in the lower part. The H+ produced in Sulfur Part could be consumed by hydrogen denitrification in Bioelectrochemical Part. Therefore, the limestone for pH adjustment in Sulfur Part was not necessary in this combined process, which avoided the problem of hardness increase. The sulfate accumulation in this combined reactor was less than that of the sulfur limestone autotrophic denitrification system. The effluent from two parts was kept neutral at optimum operation conditions. When the influent nitrate was 30 mg-N/L, the reactor could be operated efficiently at the hydraulic retention time ranged from 1.9 to 5h (corresponding minimum current was 16-3 mA), i.e. the effluent NO3(-)-N removal ranged from 90% to 100% without nitrite accumulation and the effluent sulfate concentration was lower than 170 mg/L. The maximum volume-loading rate of the reactor was 0.381 kg NO3(-)-N/(m3d). The biomass and scanning electron microscope micrographs of Sulfur Part were also analyzed.     

Nitrogen removal from on-site treated anaerobic effluents using intermittently aerated moving bed biofilm reactors at low temperature

On-site post-treatment of anaerobically pre-treated dairy parlour wastewater (DPWWe; 10 degrees C) and mixture of kitchen waste and black water (BWKWe; 20 degrees C) was studied in moving bed biofilm reactors (MBBR). The focus was on removal of nitrogen and of residual chemical oxygen demand (COD). Moreover, the effect of intermittent aeration and continuous vs. sequencing batch operation was studied. All MBBRs removed 50-60% of nitrogen and 40-70% of total COD (CODt). Complete nitrification was achieved, but denitrification was restricted by lack of carbon. Nitrogen removal was achieved in a single reactor by applying intermittent aeration. Continuous and sequencing batch operation provided similar nitrogen and COD removal, wherefore simpler continuous feeding may be preferred for on-site applications. Combination of pre-treating upflow anaerobic sludge blanket (UASB) -septic tank and MBBR removed over 92% of CODt, 99% of biological oxygen demand (BOD7), and 65-70% of nitrogen.     

DEAMOX--new biological nitrogen removal process based on anaerobic ammonia oxidation coupled to sulphide-driven conversion of nitrate into nitrite

This paper reports about the successful laboratory testing of a new nitrogen removal process called DEAMOX (DEnitrifying AMmonium OXidation) for treatment of typical strong nitrogenous wastewater such as baker's yeast effluent. The concept of this process combines the recently discovered anammox (anaerobic ammonium oxidation) reaction with autotrophic denitrifying conditions using sulphide as an electron donor for the production of nitrite from nitrate within an anaerobic biofilm. To generate sulphide and ammonia, a Upflow Anaerobic Sludge Bed (UASB) reactor was used as a pre-treatment step. The UASB effluent was split and partially fed to a nitrifying reactor (to generate nitrate) and the remaining part was directly fed to the DEAMOX reactor where this stream was mixed with the nitrified effluent. Stable process performance and volumetric nitrogen loading rates of the DEAMOX reactor well above 1000 mgN/l/d with total nitrogen removal efficiencies of around 90% were obtained after long-term (410 days) optimisation of the process. Important prerequisites for this performance are appropriate influent ratios of the key species fed to the DEAMOX reactor, namely influent N-NO(x)/N-NH(4) ratios >1.2 (stoichiometry of the anammox reaction) and influent S-H(2)S/N-NO(3) ratios >0.57 mgS/mgN (stoichiometry of the sulphide-driven denitrification of nitrate to nitrite). The paper further describes some characteristics of the DEAMOX sludge as well as the preliminary results of its microbiological characterisation.     

Nitrogen control in AO process with recirculation of solubilized excess sludge

In order to establish a sludgeless process with a nitrogen-controlled effluent, batch and continuous experiments in a lab scale anoxic-oxic (AO) process were carried out to investigate the possibility of ozonized sludge (OS) usage as a denitrification energy source. Through ozonation at an ozone dose of 1.2g O(3)/g MLVSS, 63.2% of treated MLVSS was solubilized, 12.7% of COD was lost (probably due to complete oxidation to CO(2)), and soluble COD/TN ratio of OS appeared to be only about 10.78 because ozonation released cellular proteins and other nitrogenous substances. In oxic conditions, incubation of OS supernatant with activated sludge generated nitrate without significant ammonia accumulation, which meant that rapid nitrification occurred following ammonia generation from heterotrophic degradation of nitrogen-bearing cellular substances. In anoxic conditions, externally supplied nitrate was removed at the expense of organic carbons in the OS supernatant. However, ammonia was accumulated as anoxic incubation proceeded probably because of heterotrophic degradation of nitrogenous materials as in oxic conditions. Thus it was appeared that solubilized excess sludge acted as a reducing power for denitrification but also as a nitrogen source. In addition, 24-41% of COD contained in OS supernatant were found to be consumed for denitrification. But the remaining COD was not assimilated further even in the presence of nitrate. It was concluded by a nitrogen balance analysis that the energy source contained in OS was not sufficient to completely reduce the nitrogen that was originated from OS itself to nitrogen gas.     

Characterization of sulfate-reducing granular sludge in the SANI process

Hong Kong practices seawater toilet flushing covering 80% of the population. A sulfur cycle-based biological nitrogen removal process, the Sulfate reduction, Autotrophic denitrification and Nitrification Integrated (SANI^®) process, had been developed to close the loop between the hybrid water supply and saline sewage treatment. To enhance this novel process, granulation of a Sulfate-Reducing Up-flow Sludge Bed (SRUSB) reactor has recently been conducted for organic removal and provision of electron donors (sulfide) for subsequent autotrophic denitrification, with a view to minimizing footprint and maximizing operation resilience. This further study was focused on the biological and physicochemical characteristics of the granular sulfate-reducing sludge. A lab-scale SRUSB reactor seeded with anaerobic digester sludge was operated with synthetic saline sewage for 368 days. At 1 h nominal hydraulic retention time (HRT) and 6.4 kg COD/m³-d organic loading rate, the SRUSB reactor achieved 90% COD and 75% sulfate removal efficiencies. Granular sludge was observed within 30 days, and became stable after 4 months of operation with diameters of 400–500 μm, SVI₅ of 30 ml/g, and extracellular polymeric substances of 23 mg carbohydrate/g VSS. Fluorescence in situ hybridization (FISH) analysis revealed that the granules were enriched with abundant sulfate-reducing bacteria (SRB) as compared with the seeding sludge. Pyrosequencing analysis of the 16S rRNA gene in the sulfate-reducing granules on day 90 indicated that the microbial community consisted of a diverse SRB genera, namely Desulfobulbus (18.1%), Desulfobacter (13.6%), Desulfomicrobium (5.6%), Desulfosarcina (0.73%) and Desulfovibrio (0.6%), accounting for 38.6% of total operational taxonomic units at genera level, with no methanogens detected. The microbial population and physicochemical properties of the granules well explained the excellent performance of the granular SRUSB reactor.     

Limited filamentous bulking in order to enhance integrated nutrient removal and effluent quality

Limited filamentous bulking has been proposed as a means to enhance floc size and make conditions more favorable for simultaneous nitrification/Denitrification (SND). Moreover a slightly heightened SVI is supposed to increase the removal of small particulates in the clarifier. Integrated nitrogen, phosphorus and COD removal performance under limited filamentous bulking was investigated using a bench-scale plug-flow enhanced biological phosphorus removal (EBPR) reactor fed with raw domestic wastewater. Limited filamentous bulking in this study was mainly induced by low DO levels, while other influencing factors associated with filamentous bulking (F/M, nutrients, and wastewater characteristics) were not selective for filamentous bacteria. The optimum scenario for integrated nitrogen, phosphorus and COD removal was achieved under limited filamentous bulking with an SVI level of 170-200 (associated with a DO of 1.0-1.5 mg/L). The removal efficiencies of COD, TP and NH₄⁺-N were 90%, 97% and 92%, respectively. Under these conditions, the solid-liquid separation was practically not affected and sludge loss was never observed. A well-clarified effluent with marginal suspended solids was obtained. The results of this study indicated the feasibility of limited filamentous bulking under low DO as a stimulation of simultaneous nitrification/denitrification for enhancing nutrient removal and effluent quality in an EBPR process.