Effect of humate on biological treatment of wastewater containing heavy metals

This paper presents results of investigations on the influence of humic substances (humate, HS) on the biological treatment of wastewater containing heavy metals (Cr, Cu, Fe, Mn, Ni, and Zn). Respirometric studies indicated that the investigated system complied with the Haldane model for inhibitory wastes. Chemical analyses showed that, while the soluble COD removal was high (82%), only 7% of ammonia was oxidized to nitrate. An addition of HS (500 mg L⁻¹) mitigated the inhibitory effect of the wastewater on the returned activated sludge. The system with HS complied with the Monod model for non-inhibitory wastes, and the removal of ammonia and metals was 99% and over 90%, respectively. It is suggested that an application of HS could be beneficial for treatment plants receiving wastewater streams containing heavy metals.     

Nitrification/denitrification in an intermittent aeration process for swine wastewater

Abstract

Nitrogen removal by a methane fermentation plus activated sludge process with the intermittent aeration was presented based upon a full‐scale pig farm experiment. Swine wastewater had a T‐N/BOD ratio from 0.2–0.29. The BOD concentration input to the process ranged from 1050–1608 mg l^‐1 and the T‐N concentration from 273–350 mg l^‐1. More than 90% of organic carbon was removed in each experimental run. Only small concentrations of NO₃‐N were found in the effluent and higher than 60% of the T‐N and 73% of NH₄‐N which were loaded to the intermittent aeration tank was removed. The nitrogen balance of each run was calculated. Denitrification was estimated to be accountable for 45–90% of the T‐N removed in the intermittent aeration tank. Denitrification rate increased as the BOD concentration increased (> 1300 mg l^‐1). The T‐N removal percentage was a function of the T‐N/BOD ratio of the influent. Although higher DO concentration (> 3 mg l^‐1) did not enhance the denitrification rate, nitrification did maintain at relative higher rates at a lower DO concentration (ave. 1.5 mg l^‐1). An operational condition of intermittent interval of aeration/nonaeration at 1:1 hr is better than that of the condition at 3:1 hr. As a result, T‐N and NH4‐N were removed up to 30% and 40% respectively, and the denitrification rate reached 79% in the intermittent aeration tank. An experimental run in a pilot plant on treating anaerobically pretreated swine wastewater was observed to verify simultaneous nitrification/denitrification. The results of the full‐scale plant experimentation seem to be confirmed by those obtained from the pilot plant runs.     

Impact of degradation on nitrogen transformation in a forest ecosystem of India

A study was performed selecting one protected forest and an adjacent degraded forest ecosystem to quantify the impact of forest degradation on soil inorganic nitrogen, fine root production, nitrification, N-mineralization and microbial biomass N. There were marked seasonal variations of all the parameters in the upper 0–10 and lower 10–20 cm depths. The seasonal trend of net nitrification and net N-mineralization was reverse of that for inorganic nitrogen and microbial biomass N. Net nitrification, net N-mineralization and fine root biomass values were highest in both forests during rainy season. On contrary, inorganic nitrogen and microbial biomass N were highest during summer season. There was a marked impact of forest degradation on inorganic nitrogen, fine root production nitrification, N-mineralization and microbial biomass observed. Soil properties also varied with soil depth. Fine root biomass, nitrification, N-mineralization and microbial biomass N decreased significantly in higher soil depth. Degradation causes decline in mean seasonal fine root biomass in upper layer and in lower depth by 37% and 27%, respectively. The mean seasonal net nitrification and N-mineralization in upper depth decreased by 42% and 37%, respectively and in lower depth by 42.21% and 39% respectively. Similarly microbial biomass N also decreased by 31.16% in upper layer 33.19% in lower layer.     

Biofiltration of trimethylamine, dimethylamine, and methylamine by immobilized Paracoccus sp. CP2 and Arthrobacter sp. CP1

A biofilter using granular activated carbon with immobilized Paracoccus sp. CP2 was applied to the elimination of 10–250 ppm of trimethylamine (TMA), dimethylamine (DMA), and methylamine (MA). The results indicated that the system effectively treated MA (>93%), DMA (>90%), and TMA (>85%) under high loading conditions, and the maximum degradation rates were 1.4, 1.2, and 0.9 g-N kg⁻¹ GAC d⁻¹. Among the three different amines treated, TMA was the most difficult to degrade and resulted in ammonia accumulation. Further study on TMA removal showed that the optimal pH was near neutral (6.0–8.0). The supply of high glucose (>0.1%) inhibited TMA removal, maybe due to substrate competition. However, complete TMA degradation was achieved under the co-immobilization of Paracoccus sp. CP2 and Arthrobacter sp. CP1 (96%). Metabolite analysis results demonstrated that the metabolite concentrations decreased by a relatively small 27% while the metabolite apparently increased by heterotrophic nitrification of Arthrobacter sp. CP1 in the co-immobilization biofilter.     

Developing a chloramine decay index to understand nitrification: A case study of two chloraminated drinking water distribution systems

The management of chloramine decay and the prevention of nitrification are some of the critical issues faced by water utilities that use chloramine as a disinfectant.In this study,potential association between high performance size exclusion chromatography(HPSEC)data obtained with multiple wavelength Ultraviolet(UV) detection from two drinking water distribution systems in Australia and nitrification occurrence was investigated.An increase in the absorbance signal of HPSEC profiles with UV detection at λ = 230 nm between apparent molecular weights of 200 to 1000 Da was observed at sampling sites that experienced rapid chloramine decay and nitrification while its absorbance signal at λ =254 nm decreased.A chloramine decay index(C.D.I) defined as the ratio of area beneath the HPSEC spectra at two different wavelengths of 230 and 254 nm,was used in assessing chloramine decay occurrences.The C.D.Is of waters at locations that experienced nitrification were consistently higher than locations not experiencing nitrification.A simulated laboratory study showed that the formation of nitrite/nitrate and/or soluble microbial products and/or the release of extracellular polymeric substances(EPS) during nitrification may contribute to the C.D.I.increase.These findings suggest that C.D.I derived from HPSEC with multiple wavelength UV detection could be an informative index to track the occurrence of rapid chloramine decay and nitrification.     

Assessment of the sources and transformations of nitrogen in a plain river network region using a stable isotope approach

The great spatial and temporal variability in hydrological conditions and nitrogen(N)processing introduces large uncertainties to the identification of N sources and quantifying N cycles in plain river network regions. By combining isotopic data with chemical and hydrologic measurements, we determined the relative importance of N sources and biogeochemical N processes in the Taige River in the East Plain Region of China. The river was polluted more seriously by anthropogenic inputs in winter than in summer. Manure and urban sewage effluent were the main nitrate(NO-3) sources, with the nitrification of N-containing organic materials serving as another important source of NO-3. In the downstream, with minor variations in hydrological conditions, nitrification played a more important role than assimilation for the decreasing ammonium(NH+4-N) concentrations.The N isotopic enrichment factors(ε) during NH+4utilization ranged from- 13.88‰ in March to- 29.00‰ in July. The ratio of the increase in δ18O and δ15N of river NO-3in the downstream was 1.04 in January and 0.92 in March. This ratio indicated that NO-3assimilation by phytoplankton was responsible for the increasing δ15N and δ18O values of NO-3in winter. The relationships between δ15N of particulate organic nitrogen and isotopic compositions of dissolved inorganic nitrogen indicated that the phytoplankton in the Taige River probably utilized NH+4preferentially and mainly in summer, while in winter, NO-3assimilation by phytoplankton was dominant.     

Nitrification performance evaluation of activated sludge under high potassium ion stress during high-ammonia nitrogen organic wastewater treatment

The recycling reverse osmosis（RO） membrane concentrate of some high-ammonia nitrogen（NH₄⁺-N） organic wastewater to the biological unit could cause potassium ion（K⁺） accumulation, thereby affecting the removal of NH₄⁺-N by activated sludge. Thus, the effects of high K⁺ stress on activated sludge nitrification performance was studied. The results showed that the high K⁺ stress promoted the floc sludge to produce more extr...     

活性污泥法模型的发展

详细阐述了国际水质协会（IAWQ）推出的活性污泥1号模型（ASM1）、2号模型（ASM2）、3号模型（ASM3）的组分、特点和缺陷，论述了活性污泥模型在废水处理中的重要作用，指出活性污泥模型研究、应用中的障碍。     

硝化工艺中硝化菌体的微生物结构及其选择附着生长模式

硝化处理效率低是硝化处理工艺的主要问题。硝化过程主要由硝化细菌完成，因此硝化作用的效果基本取决于硝化菌体的生长状况。文章通过硝化细菌生长方式进行探讨，提出硝化菌体在载体表面选择附着生长模式，对于理解硝化作用与硝化菌体生长的关系，硝化菌全生物膜的生物特征，从而相应地改善载体的优化设计，取得较好的硝化处理效果。     

同步硝化反硝化好氧颗粒污泥脱氮过程条件研究

具有同步硝化与反硝化功能的好氧颗粒污泥适合好氧与厌氧微生物生长代谢。反应液中氨氮浓度为201mg／L时，在6h反应周期内氨完全被氧化，出水中检测不到NO2^-—N，仅残留2mg／L的NO3^-—N。颗粒污泥优化的反应条件为：温度25～38℃；pH7～8；溶解氧浓度1～2mg／L。好氧颗粒污泥对COD和氨氮的亲和常数分别为100mg／L和2mg／L。