Horizontal-Flow Biofilm System with Step Feed for Nitrogen Removal

The aim of this study was to develop a simple biological system suitable for the treatment of dairy parlor wash waters. A novel horizontal-flow biofilm system with step feed was designed, constructed, and tested in the laboratory for organic carbon removal, nitrification, and denitrification of a synthetic dairy wastewater with average filtered chemical oxygen demand (CODf) of 2,060?mg/L, total nitrogen (TN) of 288?mg/L, and ammonia nitrogen (NH4–N) of 127?mg/L. The novel biofilm system consisted of two reactor units placed on top of one another, each comprising a stack of horizontal plastic sheets. Part of the wastewater was pumped onto Sheet 1 (top feed) and the remainder onto Sheet 11 (step feed) and flowed over the horizontal sheets down through the system. Three hydraulic loading rates were examined: 32.3, 25.1, and 19.3?L/m2?day, based on the top plan area, and the respective removals of CODf were 96, 96, and 97% and of TN, 86, 83, and 75% were achieved. The system was simple and cheap to construct and operate.     

Algae Grown on Dairy and Municipal Wastewater for Simultaneous Nutrient Removal and Lipid Production for Biofuel Feedstock

Algae grown on wastewater media are a potential source of low-cost lipids for production of liquid biofuels. This study investigated lipid productivity and nutrient removal by green algae grown during treatment of dairy farm and municipal wastewaters supplemented with CO2. Dairy wastewater was treated outdoors in bench-scale batch cultures. The lipid content of the volatile solids peaked at Day 6, during exponential growth, and declined thereafter. Peak lipid content ranged from 14–29%, depending on wastewater concentration. Maximum lipid productivity also peaked at Day 6 of batch growth, with a volumetric productivity of 17 mg/day/L of reactor and an areal productivity of 2.8?g/m2/day, which would be equivalent to 11,000 L/ha/year (1,200 gal/acre/year) if sustained year round. After 12 days, ammonium and orthophosphate removals were 96 and >99%, respectively. Municipal wastewater was treated in semicontinuous indoor cultures with 2–4 day hydraulic residence times (HRTs). Maximum lipid productivity for the municipal wastewater was 24 mg/day/L, observed in the 3-day HRT cultures. Over 99% removal of ammonium and orthophosphate was achieved. The results from both types of wastewater suggest that CO2-supplemented algae cultures can simultaneously remove dissolved nitrogen and phosphorus to low levels while generating a feedstock potentially useful for liquid biofuels production.     

HMBR法处理某黄金矿山氨氮废水试验研究

针对某黄金矿山外排水氨氮浓度较高的特点,采用复合式膜生物反应器(HMBR)系统进行处理。研究了在好氧区pH为弱酸性及中性条件下,HMBR法对氨氮和COD等典型污染物的去除特征。试验确定了HMBR法最佳工艺参数:好氧区pH值控制为6.80~7.20,DO为2~3 mg/L,动态曝气运行周期6 min(运行-间歇时间4 min^-2 min),在线化学清洗措施为“柠檬酸+水-次氯酸钠”,水力停留时间为2.34 d,HMBR出水中氨氮和COD均达到GB 8978—1996《污水综合排放标准》一级要求。该研究为HMBR法处理氨氮废水的工业化应用提供数据支持。     

Nitrate Removal in Sulfur: Limestone Pond Reactors

The feasibility of using sulfur:limestone autotrophic denitrification (SLAD) pond reactors to treat nitrate-contaminated water or wastewater after secondary treatment was investigated with four lab-scale continuously fed SLAD ponds. The start-up period, temperature effects, and effects of different feed solutions were evaluated. With an influent concentration of 30 mg NO3?–N/L at an HRT of 30 days, the pond reactors had an overall nitrate removal efficiency of 85–100%. Effluent nitrite concentrations were <0.2 mg N/L in all tests. Aerobic conditions could result in a decrease of the SLAD pH of the pond by 2 to 3 units and a large increase in sulfate production ( ～ 1600–1800?mg-SO42?/L). Under unmixed (anoxic) conditions, the pH and sulfate produced were maintained at approximately 5.5 to 5.6 and 400–600?mg-SO42?/L, respectively, in all the SLAD ponds. Temperature affected the pond reactors adversely. By assuming that a first-order reaction occurred in a SLAD pond reactor, the temperature-activity coefficient, θ was found to be 1.068. Treatment of nitrate-contaminated surface water and wastewater using SLAD pond systems is feasible only if (1) the chemical oxygen demand (COD)/nitrate–N (COD/N) ratio is low (<1.2 with an initial NO3? concentration of 30 mg-N/L), (2) sulfur:limestone granules are not covered by sediment, and (3) sulfur-utilizing but nondenitrifying bacteria (SUNDB) are greatly inhibited due to the lack of DO in the pond systems. The SLAD ponds are not feasible for the treatment of raw wastewater or surface water if they contain high concentrations of organic matters due to the possible inhibition of sulfur-based autotrophic denitrifiers by heterotrophs (including heterotrophic denitrifiers). In addition, a high sulfate and low DO concentration as well as a low pH in the SLAD effluent of the pond (even when the pond is operated in an unmixed mode) also will limit the application of SLAD pond processes.     

2,4,6 Tri-Chlorophenol Containing Wastewater Treatment Using a Hybrid-Loop Bioreactor System

A hybrid-loop bioreactor system consisting of a packed column biofilm and an aerated tank bioreactor with an effluent recycle was used for biological treatment of 2,4,6 tri-chlorophenol (TCP) containing synthetic wastewater. The effects of sludge age (solids retention time) on chemical oxygen demand (COD), TCP, and toxicity removal performance of the system were investigated for sludge ages between 5 and 30?days, while the feed COD (2600±100?mg?L?1), TCP (370±10?mg?L?1), and the hydraulic residence time (25?h) were constant. Percent TCP, COD, and toxicity removals increased with increasing sludge age resulting in nearly complete COD, TCP, and toxicity removal at sludge ages above 20?days. Biomass concentrations in the packed column and in the aeration tank increased with increasing sludge age resulting in low reactor TCP concentrations, and therefore, high TCP, COD, and toxicity removals. More than 95% of COD, TCP, and toxicity removal took place in the packed column reactor. Volumetric rates of TCP and COD removal increased due to increasing biomass and decreasing effluent TCP and COD concentrations with increasing sludge age. The specific rate of TCP removal was maximum (120?mg?TCP?gX?1?day?1) at a sludge age of 20?days. TCP inhibition was eliminated by operation of the system at sludge age above 20?days to obtain nearly complete COD, TCP, and toxicity removal.     

Treatment of Dilute Wastewaters Using a Novel Submerged Anaerobic Membrane Bioreactor

Three 3?L laboratory scale submerged anaerobic membrane bioreactors (SAMBRs) with in situ membrane cleaning due to the bubbling of recycled biogas underneath them were studied for their ability to treat dilute wastewaters. Both Mitsubishi Rayon hollow-fiber and Kubota flat sheet membranes made of polyethylene with a pore size of 0.4?μm were used in this study, and the effect of different substrates (460?mg/L of glucose or synthetic) on chemical oxygen demand (COD) performance in the SAMBR was investigated. It was found that both membranes resulted in similar COD removals (>90% soluble COD at a hydraulic retention time of 3?h), but that the transmembrane pressure across the hollow fiber membranes was higher under similar conditions. Molecular weight analysis of the feed, reactor contents, effluent, and extracellular polymers using high pressure liquid chromatography showed that the membrane filtered out most of the high MW soluble organics, resulting in high COD removals. The experimental results from the SAMBR show the potential benefits of using this novel reactor design in a biological wastewater treatment process to minimize energy use and sludge production.     

光催化技术在中低浓度氨氮废水处理中的应用

对比分析有色冶金生产过程产出的中低浓度氨氮废水处理技术,利用实验室小试考察了吹脱法、折点氯化法、药剂沉淀法和光催化技术脱除废水中氨氮的效果。结果表明,采用光催化技术处理废水,氨氮脱除率为90%～99%。在此基础上开发了一套能力为40m~3/d错流式光催化有色金属氨氮废水处理装置,将此工艺及装备用于处理氨氮浓度为266.74～1 509.79 mg/L的实际工业废水,处理后废水中氨氮含量小于20mg/L,脱除率平均为72%,最高达到93.3%。     

Simultaneous Organic and Nutrient Removal in a Naturally Ventilated Biotower Treating Presettled Municipal Wastewater

The performance of a down-flow hanging sponge (DHS) system was continuously evaluated for 1 year for enhancement of organic matter and nutrient removal in the treatment of presettled municipal wastewater. A pilot-scale DHS (24 L) was installed at a wastewater-treatment site and operated at an ambient temperature of 25°C. This paper reports on the results of a long-term monitoring of the system. The DHS system was operated at three different hydraulic retention times (HRTs), i.e., 6, 4, and 2 h. The available results showed that increasing the HRT significantly improved the removal of chemical oxygen demand (COD) fractions. The removal efficiencies of COD were 89, 80, and 56% at HRTs of 6, 4, and 2 h, respectively. Also, ammonia (NH4–N) concentration significantly decreased by increasing the HRT. Ammonia removal percentages of 99, 90, and 72% were achieved when the DHS system was operated at HRTs of 6, 4, and 2 h, respectively, but decreasing HRT exerted a slightly negative effect on the removal of total phosphorous. Scanning electron microscopy observation revealed no clogging of the sponge pores after 12 months of continuous operation. Accordingly, the results suggested that the proposed system may be a competitive solution for municipal wastewater treatment under variable conditions.     

尾矿库氰渣淋溶废水深度处理工艺研究

针对黄金矿山尾矿库氰渣淋溶的低质量浓度含氰废水,采用OOT/OCT—BAF联合工艺进行处理。其试验结果表明,在进水总氰化合物为64.45 mg/L、硫氰酸盐为22.74 mg/L、COD为76.58 mg/L、铜为72.48 mg/L的条件下,当臭氧投加量为250 mg/L、臭氧投加量分流比为2∶1、BAF的废水停留时间为20 min、气水比为3∶1时,出水总氰化合物为0.02 mg/L、硫氰酸盐完全去除、COD为5.43 mg/L、铜为0.32 mg/L、氨氮为0.79 mg/L,出水达到《GB 3838—2002地表水环境质量标准》Ⅲ类水质。     

Electrochemical Pretreatment of Wastewater from Bulk Drug Manufacturing Industry

The present study involves the treatment of high strength Bulk Drug Industry Wastewater by electrochemical method. The treatability studies were carried out with four different electrodes made of mild steel, aluminum, carbon, and stainless steel. The treatment efficiencies for chemical oxygen demand (COD)/biochemical oxygen demand (BOD), color, and heavy metal removals were assessed at different electrolysis time. A comparative study for heavy metal removal between chemical precipitation using aluminum and electrocoagulation with aluminum electrode has shown electrocoagulation to be more effective. Carbon electrode has shown COD removal of 34.0% and high BOD5f/CODf ratio of 0.581 at 120-min exposure time. Among all electrodes, aluminum was found as the most efficient in removal of color, suspended solids, and heavy metals with the least energy consumption of 95.83?Wh?kg?1?CODr and anode efficiency of 5.76?kg?COD?A?1?m?2?h?1. After electrochemical treatment, certain increase in BOD/COD ratio attributed to increase in biodegradability of wastewater. The study reveals that the wastewater could be effectively pretreated by electrochemical method.     

Optimization of Biological Nutrient Removal in a Membrane Bioreactor System

The main objective of the present study is to develop a modified membrane bioreactor (MBR) system for the treatment of municipal wastewater for the enhanced biological removal of nitrogen (N) and phosphorus (P) simultaneously with the ultimate goal of optimizing the two processes. The paper will address the implementation and optimization of the MBR process with respect to biological characteristics, operational performance, and effluent quality. The system utilizes anoxic P uptake and nitrification–denitrification in a MBR. Following optimization, the system achieved 99% chemical oxygen demand (COD), 98.4% NH3–N, 77.5% TN, and 96.3% P removal producing effluent biological oxygen demand, COD, NH3–N,NO3–N,NO2–N, and P of <3, 3, 0.4, 5.8, 0.050, and 0.18?mg/L, respectively.     

Comparison of Liquid-Liquid Extraction System and Extraction-Evaporation System for High Concentrations of Phenolic Wastewater

Liquid-liquid extraction system (LLES), including extraction section and reverse extraction section, had been applied successfully in the treatment of phenolic wastewater. In this paper, a novel pilot scale system, the extraction-evaporation system (EES) without reverse extraction section was introduced. The treatment capacity of both LLES and EES reached 4.0?m3/h. According to experimental results and economical analysis, EES had higher removal efficiency and lower treatment cost than those of LLES in the treatment of the phenolic wastewater containing 3,200–6,300?mg/L phenol, the concentrations of most resin and dye industrial effluents. The highest extractive efficiency of EES could reach 99.0% within the concentration range of 4,000–5,000?mg/L phenol, and remnant phenol in wastewater varied from 43.6 to 51.2?mg/L. The highest extracted efficiency in LLES arrived at 98.2% and the remaining phenol concentration reached 95.0?mg/L. The average removal efficiency of EES increased 1%, and the treatment cost of EES decreased 4.6%. The pretreated wastewater by EES was able to meet the demands of biological or adsorptive process. Despite that the total investment cost of EES was higher than that of LLES, treatment cost of wastewater per ton by EES was lower than that of LLES.     

Industrial Plant for Olive Mill Wastewater from Two-Phase Treatment by Chemical Oxidation

Olive-oil production generates high and variable amounts of wastewaters from the olives and olive-oil washing (OMW), resulting to great environmental impact. These waters are normally stored in large holding ponds for evaporation during the summer. The present study examines the chemical-oxidation process using ferric chloride catalyst for the activation of H2O2 (Fenton reaction). Tests have been made on an industrial scale. The final average value of chemical oxygen demand (COD) was close to 371?mg?O2?L?1 (%CODremoval = 86%, CODinitial = 2684?mg?O2?L?1), and the water produced can be used for irrigation or can be discharged directly into the municipal wastewater system for tertiary treatment.     

钼铼生产废水处理工程实例

钼铼生产废水具有高氨氮、含油和重金属的特点,采用"气浮-芬顿法-沉淀-脱氨-电絮凝"工艺处理钼铼生产废水,原水氨氮20~40g/L,COD 500~1 000 mg/L,出水氨氮<10 mg/L,COD<100mg/L,重金属<0.5mg/L,达到GB 8978-1996一级排放标准。本工程具有处理效果好和运行稳定的优势,具有较好的社会与环境效益。     

UASB Treatment of Tapioca Starch Wastewater

Feasibility of the upflow anaerobic sludge blanket (UASB) process was investigated for the treatment of tapioca starch industry wastewater. After removal of suspended solids by simple gravity settling, starch wastewater was used as a feed. Start-up of a 21.5-L reactor with diluted feed of approximately 3,000 mg∕L chemical oxygen demand (COD) was accomplished in about 6 weeks using seed sludge from an anaerobic pond treating tapioca starch wastewater. By the end of the start-up period, gas productivity of 4–5 m3/m3r?day was obtained. Undiluted supernatant wastewater with a COD concentration of 12,000–24,000 mg∕L was fed during steady-state reactor operation at an organic loading rate of 10–16 kg COD/m3r?day. The upflow velocity was maintained at 0.5 m∕h with a recirculation ratio of 4:1. COD conversion efficiencies >95% and gas productivity of 5–8 m3/m3r?day were obtained. These results indicated that removal of starch solids from wastewater by simple gravity settling was sufficient to obtain satisfactory performance of the UASB process.     

Treatment of High-Strength Pharmaceutical Wastewater and Removal of Antibiotics in Anaerobic and Aerobic Biological Treatment Processes

Anaerobic and aerobic treatment of high-strength pharmaceutical wastewater was evaluated in this study. A batch test was performed to study the biodegradability of the wastewater, and the result indicated that a combination anaerobic-aerobic treatment system was effective in removing organic matter from the high-strength pharmaceutical wastewater. Based on the batch test, a pilot-scale system composed of an anaerobic baffled reactor followed by a biofilm airlift suspension reactor was designed. At a stable operational period, effluent chemical oxygen demand (COD) from the anaerobic baffled reactor ranged from 1,432 to 2,397?mg/L at a hydraulic retention time (HRT) of 1.25 day, and 979 to 1,749?mg/L at an HRT of 2.5 day, respectively, when influent COD ranged from 9,736 to 19,862?mg/L. As a result, effluent COD of the biofilm airlift suspension reactor varied between 256 and 355?mg/L at HRTs of from 5.0 to 12.5 h. The antibiotics ampicillin and aureomycin, with influent concentrations of 3.2 and 1.0?mg/L, respectively, could be partially degraded in the anaerobic baffled reactor: ampicillin and aureomycin removal efficiencies were 16.4 and 25.9% with an HRT of 1.25 day, and 42.1 and 31.3% with HRT of 2.5 day, respectively. Although effective in COD removal, the biofilm airlift suspension reactor did not display significant antibiotic removal, and the removal efficiencies of the two antibiotics were less than 10%.     

Operational Optimization and Mass Balances in a Two-Stage MBR Treating High Strength Pet Food Wastewater

A two-stage membrane bioreactor (MBR) system was evaluated for the treatment of high strength pet food wastewater characterized by oil and grease, chemical oxygen demand (COD), biochemical oxygen demand (BOD)5, total suspended solids (TSS), total Kjeldahl nitrogen (TKN), NH4–N, and TP concentrations of 2,800, 25,000, 10,000, 4,500, 1,650, 1,300, and 370?mg/L, respectively, to meet stringent surface discharge criteria of BOD5, TSS, and NH4–N of <10?mg/L, and TP of <1?mg/L. Pretreatment of the dissolved air flotation effluent with FeCl3 at a dose of 3.5?g/L, corresponding to a Fe:P molar ratio of 1.3:1 affected TP, TSS, volatile suspended solids (VSS), COD, BOD5, and TKN reductions of 88, 72, 75, 11, 11, 36, and 17%, respectively. The two-stage MBR operating at a total hydraulic retention time of 5.3?days comprising 2.5?days in the first stage and 2.8?days in the second stage, and solids retention time of 25?days in the first stage consistently met the criteria despite wide variations in influent characteristics. Very high COD and BOD5 removal efficiencies of 97.2 and 99.8% were observed in the first stage, with an observed yield of 0.14?gVSS/gCOD. A modular approach for the quantification of simultaneous nitrification denitrification (SND) in the first-stage MBR was developed and verified experimentally. The model indicated that on average, 21% of the influent nitrogen was removed by SND and predicted nitrogen loss with an accuracy of 72%. Complete nitrification of the residual organic nitrogen and ammonia was achieved in the second-stage MBR.     

Simultaneous Removal of Nitrogen and Phosphorous from Municipal Wastewater Using Continuous-Flow Integrated Biological Reactor

A pilot-scale experiment was carried out to study the simultaneous removal of nitrogen and phosphorous from municipal wastewater by an innovative continuous-flow integrated biological reactor (CIBR) process. A three-phase separator was used in the CIBR process, which not only saved energy consumption of sludge returning, but also solved the sludge–gas separating problem. The optimal working condition was 2?h aeration, 1?h agitation, and 1?h settling, with an energy consumption of 0.23?kW?h/m3. The average removal of chemical oxygen demand (COD), ammonia nitrogen (NH4+–N), total nitrogen (TN), and total phosphorus (TP) under the optimal conditions were 72.87, 75.23, 61.25, and 68.25%, respectively. The distributing rules of dissolved oxygen, pH, mixed liquid suspended solid, COD, NH4+–N, NO3?–N, TN, and TP in each phase of CIBR was studied. It was indicated that the appropriate condition was created for the simultaneous removal of nitrogen and phosphorus in the integrated reactor. The study demonstrated the feasibility of using CIBR process for simultaneous removal of nitrogen and phosphorus at the average temperature 12.2°C.     

Computer Program Development for the Design of Integrated Fixed Film Activated Sludge Wastewater Treatment Processes

The Integrated Fixed Film Activated Sludge (IFAS) wastewater treatment systems are activated sludge biological nutrient removal processes that have been enhanced by the addition of biofilm support media into the aerobic zone of the system to obtain year round nitrification in activated sludge systems that otherwise could not support it. The objective of this study was to develop a computer package called “IFAS” that allows steady-state simulation of IFAS wastewater treatment processes based on the International Association Water Quality general model for activated sludge and empirical equations for chemical oxygen demand (COD) uptake and nitrification on integrated fixed film developed at Virginia Tech. The current version of the IFAS program supports only sponge-type media; however, the model could be modified for other media if the appropriate equations and required parameters values are known. Data obtained from IFAS sponge media pilot scale plants treating a weak municipal wastewater supplemented by sodium acetate, urea, sodium bicarbonate, and potassium phosphates and operated at different aerobic mean cells residence times were used to evaluate the model with parameter values for nitrification and COD uptake rates developed in batch studies. The model-generated ammonia and soluble COD profiles were insignificantly different statistically from the experimental data. The IFAS model satisfactorily predicts carbonaceous removal and nitrification, and has the potential to be a useful tool for scientists and engineers seeking to design and optimize either IFAS or conventional biological nutrient removal activated sludge systems.     

稀土氨氮废水治理及资源化集成技术的研究

以吸附法与化学沉淀法的集成技术组成氨氮废水处理的闭路循环系统,用自制的MgHPO4(MHP)为吸附剂,对NH4+浓度为5175mg/L稀土硫酸铵废水进行了氨氮吸附性能实验,研究发现pH、MHP的投加量和氨氮初始浓度是影响氨氮去除效果的关键因素。在室温下,调节反应体系pH=9.5,MHP用量按摩尔比n(MHP)∶n(NH4+)=2∶1投料,搅拌吸附30min,氨氮去除率可达85.7%,且氨氮初始浓度越高,吸附效果越好。MHP再生与循环使用实验表明,MAP焙烧可使MHP再生,同时可回收高浓度的氨水,MHP循环使用三次,氨氮的去除率均在70%以上。如果采用MHP二级吸附法后,再用MAP沉淀法处理废水,可使出水氨氮浓度降低为87mg/L,累计氨氮去除率可达到98%以上。