Mg2+ improves biomass production from soybean wastewater using purple non-sulfur bacteria

Soybean wastewater was used to generate biomass resource by use of purple non-sulfur bacteria (PNSB). This study investigated the enhancement of PNSB cell accumulation in wastewater by Mg²⁺ under the light-anaerobic condition. Results showed that with the optimal Mg²⁺ dosage of 10 mg/L, biomass production was improved by 70% to 3630 mg/L, and biomass yield also was improved by 60%. Chemical Oxygen Demand (COD) removal reached above 86% and hydraulic retention time was shortened from 96 to 72 hr. The mechanism analysis indicated that Mg²⁺ could promote the content of bacteriochlorophyll in photosynthesis because Mg²⁺ is the bacteriochlorophyll active center, and thus improved adenosine triphosphate (ATP) production. An increase of ATP production enhanced the conversion of organic matter in wastewater into PNSB cell materials (biomass yield) and COD removal, leading to more biomass production. With 10 mg/L Mg²⁺, bacteriochlorophyll content and ATP production were improved by 60% and 33% respectively.     

Mg2+ improves biomass production from soybean wastewater using purple non-sulfur bacteria

Soybean wastewater was used to generate biomass resource by use of purple non-sulfur bacteria(PNSB). This study investigated the enhancement of PNSB cell accumulation in wastewater by Mg2+under the light-anaerobic condition. Results showed that with the optimal Mg2+dosage of 10 mg/L, biomass production was improved by 70% to 3630 mg/L,and biomass yield also was improved by 60%. Chemical Oxygen Demand(COD) removal reached above 86% and hydraulic retention time was shortened from 96 to 72 hr. The mechanism analysis indicated that Mg2+could promote the content of bacteriochlorophyll in photosynthesis because Mg2+is the bacteriochlorophyll active center, and thus improved adenosine triphosphate(ATP) production. An increase of ATP production enhanced the conversion of organic matter in wastewater into PNSB cell materials(biomass yield) and COD removal, leading to more biomass production. With 10 mg/L Mg2+, bacteriochlorophyll content and ATP production were improved by 60% and 33% respectively.     

添加原水改善SBR工艺处理猪场废水厌氧消化液性能

采用序批式反应器(SBR)工艺直接处理猪场废水厌氧消化液,处理系统的效率较低,COD去除率仅有10%左右,NH₄⁺-N去除率70%左右;处理出水水质较差,出水COD高于1 000mg/L,出水NH₄⁺-N在200mg/L左右;处理系统的工作不稳定,效能逐渐恶化.在猪场废水厌氧消化液中添加部分未经厌氧消化的猪场废水(原水),处理系统的处理效率明显提高,COD去除率高于80%,出水COD降到250～350mg/L;NH₄⁺-N去除率高于99%,出水NH₄⁺-N小于10mg/L;处理系统的稳定性也得到增强.添加原水后,猪场废水厌氧消化液的BOD₅/COD比值从0.19上升到0.54,BOD₅/TN比值从0.28上升到2.04,增加了微生物生长和反硝化所需的碳源,强化了反硝化作用,不仅提高了总氮去除效率,而且通过回补碱度,维持了处理系统的pH值稳定.     

Bio-remediation of acephate–Pb(II) compound contaminants by Bacillus subtilis FZUL-33

Removal of Pb~(2+)and biodegradation of organophosphorus have been both widely investigated respectively. However, bio-remediation of both Pb~(2+)and organophosphorus still remains largely unexplored. Bacillus subtilis FZUL-33, which was isolated from the sediment of a lake, possesses the capability for both biomineralization of Pb~(2+)and biodegradation of acephate. In the present study, both Pb~(2+)and acephate were simultaneously removed via biodegradation and biomineralization in aqueous solutions.Batch experiments were conducted to study the influence of p H, interaction time and Pb~(2+)concentration on the process of removal of Pb2+. At the temperature of 25°C, the maximum removal of Pb~(2+)by B. subtilis FZUL-33 was 381.31 ± 11.46 mg/g under the conditions of p H 5.5, initial Pb~(2+)concentration of 1300 mg/L, and contact time of 10 min. Batch experiments were conducted to study the influence of acephate on removal of Pb~(2+)and the influence of Pb2+on biodegradation of acephate by B. subtilis FZUL-33. In the mixed system of acephate–Pb2+, the results show that biodegradation of acephate by B. subtilis FZUL-33 released PO43+, which promotes mineralization of Pb2+. The process of biodegradation of acephate was affected slightly when the concentration of Pb2+was below 100 mg/L. Based on the results, it can be inferred that the B. subtilis FZUL-33 plays a significant role in bio-remediation of organophosphorus-heavy metal compound contamination.     

Simultaneous removal of Cu(II) and Cr(VI) by Mg–Al–Cl layered double hydroxide and mechanism insight

Mg–Al–Cl layered double hydroxide (Cl-LDH) was prepared to simultaneously remove Cu(II) and Cr(VI) from aqueous solution. The coexisting Cu(II) (20 mg/L) and Cr(VI) (40 mg/L) were completely removed within 30 min by Cl-LDH in a dosage of 2.0 g/L; the removal rate of Cu(II) was accelerated in the presence of Cr(VI). Moreover, compared with the adsorption of single Cu(II) or Cr(VI), the adsorption capacities of Cl-LDH for Cu(II) and Cr(VI) can be improved by 81.05% and 49.56%, respectively, in the case of coexisting Cu(II) (200 mg/L) and Cr(VI) (400 mg/L). The affecting factors (such as solution initial pH, adsorbent dosage, and contact time) have been systematically investigated. Besides, the changes of pH values and the concentrations of Mg²⁺ and Al³⁺ in relevant solutions were monitored. To get the underlying mechanism, the Cl-LDH samples before and after adsorption were thoroughly characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. On the basis of these analyses, a possible mechanism was proposed. The coadsorption process involves anion exchange of Cr(VI) with Cl⁻ in Cl-LDH interlayer, isomorphic substitution of Mg²⁺ with Cu²⁺, formation of Cu₂Cl(OH)₃ precipitation, and the adsorption of Cr(VI) by Cu₂Cl(OH)₃. This work provides a new insight into simultaneous removal of heavy metal cations and anions from wastewater by Cl-LDH.     

Nitrogen removal and simultaneous nitrification and denitrification in a fluidized bed step-feed process

For urban wastewater treatment, we conducted a novel four-stage step-feed wastewater treatment system combined with a fluidized bed laboratory experiment to investigate chemical oxygen demand (COD), NH₄⁺-N, and total nitrogen (TN) removal performance. The removal rates of COD, NH₄⁺-N and TN were 88.2%, 95.7%, and 86.4% with effluent concentrations of COD, NH₄⁺-N and TN less than 50, 8, and 10 mg/L, respectively. Biomass and bacterial activities were also measured, with results showing more nitrobacteria in the activated sludge than in the biofilm; however, bacterial activity of the biofilm biomass and the activated sludge were similar. Nitrogen concentrations during the process were also detected, with simultaneous nitrification and denitrification found to be obvious.     

Simultaneous denitrification and denitrifying phosphorus removal in a full-scale anoxic–oxic process without internal recycle treating low strength wastewater

Performance of a full-scale anoxic-oxic activated sludge treatment plant(4.0×10~5 m~3/day for the first-stage project) was followed during a year.The plant performed well for the removal of carbon,nitrogen and phosphorus in the process of treating domestic wastewater within a temperature range of 10.8℃ to 30.5℃.Mass balance calculations indicated that COD utilization mainly occurred in the anoxic phase,accounting for 88.2% of total COD removal.Ammonia nitrogen removal occurred 13.71% in the anoxic zones and 78.77% in the aerobic zones.The contribution of anoxic zones to total nitrogen(TN) removal was 57.41%.Results indicated that nitrogen elimination in the oxic tanks was mainly contributed by simultaneous nitrification and denitrification(SND).The reduction of phosphorus mainly took place in the oxic zones,51.45% of the total removal.Denitrifying phosphorus removal was achieved biologically by 11.29%.Practical experience proved that adaptability to gradually changing temperature of the microbial populations was important to maintain the plant overall stability.Sudden changes in temperature did not cause paralysis of the system just lower removal efficiency,which could be explained by functional redundancy of microorganisms that may compensate the adverse effects of temperature changes to a certain degree.Anoxic-oxic process without internal recycling has great potential to treat low strength wastewater(i.e.,TN 35 mg/L) as well as reducing operation costs.     

The biological effect of metal ions on the granulation of aerobic granular activated sludge

As a special biofilm structure, microbial attachment is believed to play an important role in the granulation of aerobic granular activated sludge (AGAS). This experiment was to investigate the biological effect of Ca^2 +, Mg^2 +, Cu^2 +, Fe^2 +, Zn^2 +, and K⁺ which are the most common ions present in biological wastewater treatment systems, on the microbial attachment of AGAS and flocculent activated sludge (FAS), from which AGAS is always derived, in order to provide a new strategy for the rapid cultivation and stability control of AGAS. The result showed that attachment biomass of AGAS was about 300% higher than that of FAS without the addition of metal ions. Different metal ions had different effects on the process of microbial attachment. FAS and AGAS reacted differently to the metal ions as well, and in fact, AGAS was more sensitive to the metal ions. Specifically, Ca^2 +, Mg^2 +, and K⁺ could increase the microbial attachment ability of both AGAS and FAS under appropriate concentrations, Cu^2 +, Fe^2 +, and Zn^2 + were also beneficial to the microbial attachment of FAS at low concentrations, but Cu^2 +, Fe^2 +, and Zn^2 + greatly inhibited the attachment process of AGAS even at extremely low concentrations. In addition, the acylated homoserine lactone (AHL)-based quorum sensing system, the content of extracellular polymeric substances and the relative hydrophobicity of the sludges were greatly influenced by metal ions. As all these parameters had close relationships with the microbial attachment process, the microbial attachment may be affected by changes of these parameters.     

Denitrification and biofilm growth in a pilot-scale biofilter packed with suspended carriers for biological nitrogen removal from secondary effluent

Tertiary denitrification is an effective method for nitrogen removal from wastewater. A pilot-scale biofilter packed with suspended carriers was operated for tertiary denitrification with ethanol as the organic carbon source. Long-term performance, biokinetics of denitrification and biofilm growth were evaluated under filtration velocities of 6, 10 and 14 m/hr. The pilot-scale biofilter removed nitrate from the secondary effluent effectively, and the nitrate nitrogen (NO₃-N) removal percentage was 82%, 78% and 55% at the filtration velocities of 6, 10 and 14 m/hr, respectively. At the filtration velocities of 6 and 10 m/hr, the nitrate removal loading rate increased with increasing influent nitrate loading rates, while at the filtration velocity of 14 m/hr, the removal loading rate and the influent loading rate were uncorrelated. During denitrification, the ratio of consumed chemical oxygen demand to removed NO₃-N was 3.99–4.52 mg/mg. Under the filtration velocities of 6, 10 and 14 m/hr, the maximum denitrification rate was 3.12, 4.86 and 4.42 g N/(m²·day), the half-saturation constant was 2.61, 1.05 and 1.17 mg/L, and the half-order coefficient was 0.22, 0.32 and 0.24 (mg/L)^1/2/min, respectively. The biofilm biomass increased with increasing filtration velocity and was 2845, 5124 and 7324 mg VSS/m² at filtration velocities of 6, 10 and 14 m/hr, respectively. The highest biofilm density was 44 mg/cm³ at the filtration velocity of 14 m/hr. Due to the low influent loading rate, biofilm biomass and thickness were lowest at the filtration velocity of 6 m/hr.     

Fluoride removal by Al, Ti, and Fe hydroxides and coexisting ion effect

Batch experiments were conducted to evaluate fluoride removal by Al,Fe,and Ti-based coagulants and adsorbents,as well as the effects of coexisting ions and formation of aluminum–fluoride complexes on fluoride removal by co-precipitation with alum(Al_2(SO_4)_3·18H_2O).Aluminum sulfate was more efficient than the other coagulants for fluoride removal in the pH range between 6 and 8.Nano-crystalline TiO_2 was more effective for fluoride removal than Al and Fe hydroxides in a pH range of 3–5.Coexisting anions in water decreased the removal of fluoride in the order:phosphate(2.5 mg/L) arsenate(0.1 mg/L) bicarbonate(200 mg/L) sulfate(100 mg/L) = nitrate(100 mg/L) silicate(10 mg/L) at a pH of 6.0.The effect of silicate became more significant at pH 7.0.Calcium and magnesium improved the removal of fluoride.Zeta-potential measurements determined that the adsorption of fluoride shifted the PZC of Al(OH)_3 precipitates from 8.9 to 8.4,indicating the chemical adsorption of fluoride at the surface.The presence of fluoride in solution significantly increased the soluble aluminum concentration at pH 6.5.A Visual MINTEQ modeling study indicated that the increased aluminum solubility was caused by the formation of AlF~(2+),AlF~(+2),and AlF_3complexes.The AlF_x complexes decreased the removal of fluoride during co-precipitation with aluminum sulfate.     

Phosphate recovery from anaerobic digester effluents using CaMg(OH)4

Dolomite lime(DL)(CaMg(OH)_4) was used as an economical source of Mg~(2+)for the removal and recovery of phosphate from an anaerobic digester effluent of a municipal wastewater treatment plant(MWWTP) wastewater. Batch precipitation results determined that phosphate was effectively reduced from 87 to less than 4 mg-P/L when the effluent water was mixed with 0.3 g/L of DL. The competitive precipitation mechanisms of different solids in the treatment system consisting of Ca~(2+)–Mg~(2+)–NH_4~+–PO_4~(3-)CO_3~(2-)were determined by comparing model predictions with experimental results. Thermodynamic model calculations indicated that hydroxyapatite(Ca_(10)(PO_4)_6(OH)_2), Ca_4H(PO_4)_3?3H_2O, Ca_3(PO_4)_2(beta), and Ca_3(PO_4)_2(am2)were more stable than struvite(MgNH_4PO_3?6H_2O) and calcite(CaCO_3). However, X-ray diffraction(XRD) analysis determined the formation of struvite and calcite minerals in the treated effluent. Kinetic experimental results showed that most of the phosphate was removed from synthetic effluent containing NH_4~+within 2 hr, while only 20% of the PO_4~(3-)was removed in the absence of NH_4~+after 24 hr of treatment. The formation of struvite in the DL-treated effluent was due to the rapid precipitation rate of the mineral. The final pH of the DL-treated effluent significantly influenced the mass ratio of struvite to calcite in the precipitates. Because more calcite was formed when the p H increased from 8.4 to 9.6, a p H range of 8.0–8.5 should be used to produce solid with high PO_4~(3-)content. This study demonstrated that DL could be used for effective removal of phosphate from the effluent and that resultant precipitates contained high content of phosphate and ammonium.     

Kinetics and mechanism of hexavalent chromium removal by basic oxygen furnace slag

Basic oxygen furnace slag(BOFS) has the potential to remove hexavalent chromium(Cr(VI))from wastewater by a redox process due to the presence of minerals containing Fe2+. The effects of the solution p H, initial Cr(VI) concentration, BOFS dosage, BOFS particle size, and temperature on the removal of Cr(VI) was investigated in detail through batch tests. The chemical and mineral compositions of fresh and reacted BOFS were characterized using scanning electron microscope(SEM) equipped with an energy dispersive spectrometer(EDS)system and X-ray diffractometer(XRD). The results show that Cr(VI) in wastewater can be efficiently removed by Fe2+released from BOFS under appropriate acidic conditions. The removal of Cr(VI) by BOFS significantly depended on the parameters mentioned above. The reaction of Cr(VI) with BOFS followed the pseudo-second-order kinetic model. Fe2+responsible for Cr(VI) removal was primarily derived from the dissolution of Fe O and Fe3O4 in BOFS. When H2SO4 was used to adjust the solution acidity, gypsum(Ca SO4·2H2O)could be formed and become an armoring precipitate layer on the BOFS surface, hindering the release of Fe2+and the removal of Cr(VI). Finally, the main mechanism of Cr(VI) removal by BOFS was described using several consecutive reaction steps.     

Using a novel adsorbent macrocyclic compound cucurbit[8]uril for Pb removal from aqueous solution

In this study, cucurbit[8]uril (CB[8]) was utilized as a kind of new adsorbent to remove Pb^2 + ions from aqueous solution. With the solution pH increased from 2 to 6, the removal efficiency of adsorption increased from 55.6% to 74.5%correspondingly. The uptake of Pb^2 + increased rapidly in the initial 30 min, and then the adsorption rate became slower. The Pseudo-second order model could be used to interpret the adsorption kinetics satisfactorily; and the rate determining step in Pb^2 + adsorption onto CB[8] was the external mass transfer step. Equilibrium isotherm study reveals that the Langmuir model gave a better fitting result than Freundlich model. The maximum adsorption capacity calculated by the Langmuir model was 152.67 mg/g for 298 K, 149.70 mg/g for 313 K and 136.42 mg/g for 323 K, respectively. The adsorption is a spontaneous process of exothermic nature. The effect of the adsorbent dosage and the influences of solution pH and co-existing cations were also investigated. The CB[8] was synthesized and characterized by ¹H NMR, IR, ESI-MS spectra, SEM-EDAX, Zeta-potential and BET-analysis. The adsorption mechanism was due to the coordination between CB[8] molecule and Pb^2 + ions.     

Anoxic phosphorus removal in a pilot scale anaerobic-anoxic oxidation ditch process

The anaerobic-anoxic oxidation ditch (A²/O OD) process is popularly used to eliminate nutrients from domestic wastewater. In order to identify the existence of denitrifying phosphorus removing bacteria (DPB), evaluate the contribution of DPB to biological nutrient removal, and enhance the denitrifying phosphorus removal in the A²/O OD process, a pilot-scale A²/O OD plant (375 L) was conducted. At the same time batch tests using sequence batch reactors (12 L and 4 L) were operated to reveal the significance of anoxic phosphorus removal. The results indicated that: The average removal efficiency of COD, NH₄⁺, PO₄³⁻, and TN were 88.2%, 92.6%, 87.8%, and 73.1%, respectively, when the steady state of the pilotscale A²/O OD plant was reached during 31–73 d, demonstrating a good denitrifying phosphorus removal performance. Phosphorus uptake took place in the anoxic zone by poly-phosphorus accumulating organisms NO₂⁻ could be used as electron receptors in denitrifying phosphorus removal, and the phosphorus uptake rate with NO₂⁻ as the electron receptor was higher than that with NO₃⁻ when the initial concentration of either NO₂⁻ or NO₃⁻ was 40 mg/L.     

膜曝气生物膜反应器同步硝化反硝化研究

炭膜作为膜曝气生物膜反应器膜组件处理人工合成废水,在单一反应器内实现了同时去碳脱氮.结果表明,当进水COD和NH^＋₄-N浓度分别为338 mg/L和75 mg/L,HRT为14 h,炭膜腔内压力为13.6 kPa时,COD、NH⁺₄-N和TN的去除效率分别为82.5%、 95.1%和84.2%.但是在反应器运行的后期TN去除效率明显下降,主要是因为高有机负荷导致无纺布上的微生物过度繁殖,严重影响了硝化过程的进行.通过荧光原位杂交和扫描电镜技术观察生物膜微生物结构,得出厌氧或兼氧菌主要分布在生物膜外层的缺氧区,而氨氧化菌主要分布在生物膜内层的好氧区.硝化细菌和反硝化细菌在生物膜内的共存实现了炭膜曝气生物膜反应器的同步硝化反硝化.     

地下渗滤处理村镇生活污水的中试

以红壤土作为填充土壤,在2cm/d的水力负荷下,进行了地下渗滤系统处理村镇生活污水的现场中试.结果表明,地下渗滤系统对COD、氨氮、总磷和总氮有着良好的去除效果,去除率分别达到84.7%、70.0%、98.0%和77.7%,出水COD、氨氮、总磷和总氮的平均浓度分别为11.7mg/L、4.0mg/L、0.04mg/L、4.7mg/L,达到建设部颁发的生活杂用水水质标准对总氮去除机理的分析表明,由硝化/反硝化实现生物脱氮是地下渗滤系统去除总氮的主要途径.在本中试系统中,反硝化效果良好但硝化效果不够理想,改善土壤环境以促进硝化作用是提高总氮去除率的关键.对土壤中氧化还原电位的测定结果表明,土壤内部的还原性质是阻碍硝化反应进行的主要原因.     

微生物燃料电池利用甘薯燃料乙醇废水产电的研究

利用空气阴极微生物燃料电池(MFC)处理甘薯燃料乙醇废水,以COD为5000mg/L的废水做底物,获得的最大电功率密度为334.1mW/m2,库仑效率(CE)为10.1%,COD去除率为92.2%.实验进一步考察了磷酸缓冲液(PBS)浓度和废水浓度对MFC产电性能的影响.PBS含量从50mmol/L增加到200mmol/L,MFC输出的最大电功率密度提高了33.4%,CE增加26.0%,但PBS对废水的COD去除率影响不大.含50mmol/LPBS的废水COD从625mg/L增加到10000mg/L,COD去除率和MFC输出的最大电功率密度在废水浓度为5000mg/L处均获得最大值,但CE值有降低的趋势,从28.9%变化至10.3%.这些结果表明,MFC可以在处理甘薯燃料乙醇废水的同时获得电能;增大PBS浓度能提高MFC的产电性能;MFC输出的最大电功率密度随废水COD增加而增大,但废水浓度过高会引起酸化使MFC产电性能下降.     

Effect of organic matter on phosphorus recovery from sewage sludge subjected to microwave hybrid pretreatment

Microwave (MW) hybrid processes are able to disrupt the flocculent structure of complex waste activated sludge, and help promote the recovery of phosphorus as struvite. In this study, to optimize struvite yield, (1) the characteristics of matter released in MW-hybrid treatments were compared, including MW, MW-acid, MW-alkali, MW-H₂O₂, and MW-H₂O₂-alkali. The results showed that selective release of carbon, nitrogen, phosphorus, Ca^2 +, and Mg^2 + achieved by sludge pretreatment using MW-hybrid processes. MW-H₂O₂ is the recommended sludge pretreatment process for phosphorus recovery in the form of struvite. The ratio of Mg^2 +:NH₄⁺-N:PO₄^3 −-P was 1.2:2.9:1 in the supernatant. (2) To clarify the effects of organic matter on struvite recovery, the composition and molecular weight distribution of organic matters were analyzed. Low molecular weight COD was found to facilitate the removal rate of NH₄⁺-N and PO₄³-P via crystallization, and the amorphous struvite crystals (< 1 kDa) from the filtered solutions had high purity. Therefore, the present study reveals the necessity of taking into consideration the interference effect of high molecular weight organic matters during struvite crystallization from sewage sludge.     

UASB反应器处理维生素B12淀粉混合废水的研究

为考察厌氧技术处理维生素Ｂ１２淀粉混合废水的可行性,进行了采用ＵＡＳＢ反应器处理废水研究,结果表明,在中温条件下,当进水ＣＯＤ浓度为１００００－１２０００ｍｇ／Ｌ时,ＣＯＤ容积负荷可达到３０ｋｇ／（ｍ＾３．ｄ）,ＣＯＤ去除率为８０％,容积产气率为１６．８０ｍ＾３／（ｍ＾３．ｄ）。     

The application of iron mesh double layer as anode for the electrochemical treatment of Reactive Black 5 dye

In this work a novel anode configuration consisting of an iron mesh double layer is proposed for the electrochemical treatment of wastewater. The removal of Reactive Black 5 dye(RB5) from synthetic contaminated water was used as a model system. At a constant anode surface area, identical process operating parameters and batch process mode, the iron mesh double layer electrode showed better performance compared to the conventional single layer iron mesh. The double layer electrode was characterized by RB5 and chemical oxygen demand(COD) removal efficiency of 98.2% and 97.7%, respectively, kinetic rate constant of 0.0385/min, diffusion coefficient of 4.9 × 10~(-5)cm~2/sec and electrical energy consumption of 20.53 kWh/kgdye removed. In the continuous flow system, the optimum conditions suggested by Response Surface Methodology(RSM) are: initial solution p H of 6.29,current density of 1.6 m A/cm~2, electrolyte dose of 0.15 g/L and flow rate of 11.47 m L/min which resulted in an RB5 removal efficiency of 81.62%.