An innovative wood-chip-framework substrate used as slow-release carbon source to treat high-strength nitrogen wastewater

Removal of nitrogen in wastewater before discharge into receiving water courses is an important consideration in treatment systems. However, nitrogen removal efficiency is usually limited due to the low carbon/nitrogen (C/N) ratio. A common solution is to add external carbon sources, but amount of liquid is difficult to determine. Therefore, a combined wood-chip-framework substrate (with wood, slag and gravel) as a slow-release carbon source was constructed in baffled subsurface-flow constructed wetlands to overcome the problem. Results show that the removal rate of ammonia nitrogen (NH₄⁺-N), total nitrogen (TN) and chemical oxygen demand (COD) could reach 37.5%–85%, 57.4%–86%, 32.4%–78%, respectively, indicating the combined substrate could diffuse sufficient oxygen for the nitrification process (slag and gravel zone) and provide carbon source for denitrification process (wood-chip zone). The nitrification and denitrification were determined according to the location of slag/gravel and wood-chip, respectively. Nitrogen removal was efficient at the steady phase before a shock loading using slag-wood-gravel combined substrate because of nitrification–denitrification process, while nitrogen removal was efficient under a shock loading with wood-slag-gravel combined substrate because of ANAMMOX process. This study provides a new idea for wetland treatment of high-strength nitrogen wastewater.     

Temporal and spatial variation of nitrogen and phosphorus and eutrophication assessment for a typical arid river—Fuyang River in northern China

Based on water quality surveys over 2 years(July to December,in 2014 and 2015) in a typical arid river in northern China the Xingtai segment of the Fuyang River basin — the variation of nitrogen(N) and phosphorus(P) was analyzed.The extent of water eutrophication of this segment was also assessed using a universal index formula for eutrophic evaluation and a logarithmic power function.The results showed that the average concentration of total N(TN) was 27.2 mg/L(NH_3-N,63.5%),total P(TP) was 2.0 mg/L(solution reactive phosphorus,68.8%).Temporal and spatial variations of N and P in this segment were observed.Concentrations of N and P in the arid season were higher than those in the rainy season.Spatially,the N and P concentrations followed the same trend;i.e.,higher in the city segment than in the suburbs,and decreasing along the river.The water eutrophication in the studied segment reached extremely high levels at all times(eutrophication index ≥76.3).Spatially,its trend was clearly linked with N and P.Water shortage,pollution accumulation and a weak self-purification function are the main reasons for the prominent eutrophication in this segment.     

洱海表层沉积物中磷形态分布及pH、DO影响的分析

研究了洱海代表性区域表层沉积物中总磷分布及不同形态磷赋存特征,探讨了pH值及溶解氧对沉积物中总磷和各形态磷赋存状态的影响。结果表明洱海表层沉积物中总磷和不同形态磷分布不均,总磷含量湖心高于湖口,湖心区域闭蓄态磷(BD-P和Al-P)和生物有效态磷占总磷的比例较高,更容易受pH和DO的影响,碱性和厌氧条件会增加洱海湖心底泥中磷的潜在释放能力。     

5种植物沉床系统对富营养化水体修复效果研究

以狐尾藻、马来眼子菜、金鱼藻、伊乐藻和苦草5种沉水植物为试验材料,构建以沉水植物为核心的人工沉床,探讨富营养化水体中沉水植物的生长状况和沉水植物沉床系统对氮、磷和COD_(Mn)的净化效果。结果表明:5种沉水植物在富营养水体中生长良好,生物量明显增加,以金鱼藻生物量最大。5种沉水植物沉床系统对富营养化水体中的TP、TN和NH_4~+-N去除率较高,均值分别为70.16%、79.60%、79.82%,而对COD_(Mn)的去除率较低,平均为39.74%;其中金鱼藻沉床系统对富营养化水体中的TP、TN、氨氮、COD_(Mn)去除率均最高,分别为79.76%、85.23%、85.81%和46.16%。因此,金鱼藻沉床系统对富营养化水体修复效果最好,同时金鱼藻也是该沉床系统的优选植物。     

Heavy metal removal from industrial effluents by sorption on cross-linked starch: chemical study and impact on water toxicity

Batch sorption experiments using a starch-based sorbent were carried out for the removal of heavy metals present in industrial water discharges. The influence of contact time, mass of sorbent and pollutant load was investigated. Pollutant removal was dependent on the mass of sorbent and contact time, but independent of the contaminant load. The process was uniform, rapid and efficient. Sorption reached equilibrium in 60 min irrespective of the metal considered (e.g. Zn, Pb, Cu, Ni, Fe and Cd), reducing concentrations below those permitted by law. The material also removed residual turbidity and led to a significant decrease in the residual chemical oxygen demand (COD) present in the industrial water discharge. The germination success of lettuce (Lactuca sativa) was used as a laboratory indicator of phytotoxicity. The results show that the sorption using a starch-based sorbent as non-conventional material, is a viable alternative for treating industrial wastewaters.     

Dynamic model of Lake Chozas (León, NW Spain)—Decrease in eco-exergy from clear to turbid phase due to introduction of exotic crayfish

We developed a dynamic model of the phosphorus cycle in Lake Chozas, a small shallow water body in León (NW Spain). The calibrated model simulated seasonal dynamics of phosphorus concentrations in major components of the lake's ecological network before and after 1997, the year when an invasive allochthonous crustacean, the Louisiana red swamp crayfish (Procambarus clarkii), was introduced into the lake. The shift from clean to turbid phase, due to grazing by crayfish on submerged vegetation, caused a gradual decrease in eco-exergy, reflecting an increase in entropy, related to breakdown of ecosystem internal equilibria. This case study verifies the hypothesis of Marchi et al. (2010) that, after an initial relatively stable state, the allochthonous species may cause an increase in entropy indicating perturbation of the ecosystem.     

Eutrophication: Early warning signals,ecosystem-level and societal responses,and ways forward: This article belongs to Ambio’s 50th Anniversary Collection. Theme: Eutrophication

Eutrophication, i.e. nutrient over-enrichment, has been a topic for academic and societal debate for the past five decades both on land and in aquatic systems fed by nutrients as diffuse loading from agricultural lands and as wastewater from industrial and municipal point-sources. The use of nutrients (primarily nitrogen and phosphorus) in excess became a problem with the onset of large-scale production and use of artificial fertilizers after World War II, and the effects on the aquatic environment became obvious some two to three decades later. In this Perspective, four seminal papers on eutrophication are discussed in light of the current knowledge of the problem, including future perspectives and outlooks in the light of global climate change and the demand for science-based holistic ecosystem-level policies and management options.     

Adsorption and membrane separation for removal and recovery of volatile organic compounds

Volatile organic compounds(VOCs) are a crucial kind of pollutants in the environment due to their obvious features of severe toxicity, high volatility, and poor degradability. It is particularly urgent to control the emission of VOCs due to the persistent increase of concentration and the stringent regulations. In China, clear directions and requirements for reduction of VOCs have been given in the “national plan on environmental improvement for the 13th Five-Year Plan period”. Therefore, the de...     

Predicting future effects from nutrient abatement and climate change on phosphorus concentrations in Lake Bourget, France

Like many temperate European lakes, Lake Bourget (France) has suffered from eutrophication during the second half of the last century. Due to a remarkable restoration program, the lake has been recovering for the past 25 years after a massive decrease in total phosphorus (TP) loading. TP concentrations have decreased from about 100-120 to 20-25 μg/L. Additional efforts are, however, still required to obtain a perennially sustainable good ecological status and model parameterisation of fluxes can assist in predicting future outcomes, especially in the context of global warming. In this paper, a dynamic model (MeroLakeMab) was developed and tested with the purpose to reconstruct the loading history of Lake Bourget and to predict TP concentrations during scenarios of increased temperature, decreased water runoff and decreased P loading. Simulations suggested that the historical TP loading decrease may have been as extensive as 88%. Decreases in water discharge to Lake Bourget at magnitudes forecasted by the Intergovernmental Panel on Climate Change (IPCC) would not affect TP concentrations notably, but marked concentration changes could, however, occur if decreases in runoff would have a strong impact on the TP loading. Increasing temperature effects on yearly mean TP concentrations in the water column would be very small compared to effects from changes in the TP loading. Predictions such as these could be instrumental for future successful lake management.     

白洋淀沉积物中磷的存在形态及垂直变化规律研究

湖泊沉积物中磷的含量及其形态分布是影响湖泊营养化进程的极为重要因素,对研究湖泊营养化等环境问题具有重要意义。采用化学连续提取分析法,对白洋淀环淀中村水域不同地点的沉积物中磷的形态及其在垂直方向上的变化进行了研究。结果表明,研究区域内,环淀中村水域表层沉积物总磷（TP）质量分数在544.424～608.197mg·kg-1之间,无机磷（IP）是沉积物中磷的主要形态,有机磷（OP）质量分数较小,约占10%～27%,无机磷中钙磷（Ca-P）占的比例相对较大,在质量分数上约占75.8%～94.1%。从各形态磷质量分数的变化范围来看,Ca-P〉OP〉Fe/Al-P;人类活动对湖泊沉积物中磷的形态及其水平和垂向变化影响很大。