Embedded reservoir and constructed wetland for drinking water source protection: Effects on nutrient removal and phytoplankton succession

An embedded reservoir that provides an efficient nutrient removal system protects drinking water.However,embedded reservoirs are rarely used in eutrophic shallow lakes because of their undetermined nutrient retention efficiency and unknown effects by the phytoplankton community.In this study,we aim to investigate the nutrient retention and algae succession in an embedded reservoir and adjacent wetland from April 2017 to September 2018 in the eastern part of Lake Taihu,China.More than 40% of total phosphorus(TP) and 45% of particulate phosphorous entering the reservoir were retained semiannually,and the highest TP removal efficiency was achieved in the reservoir during autumn with an average value of 53.3% ± 9.9%.The overall nitrogen retention efficiency(21.7% ± 37.8%) was lower than that of TP(41.8% ± 27.8%).Similar trends were obtained in the wetland area.An important pathway for phosphorus removal is through particulate matter retention.Our study revealed that nutrient retention mechanisms in the reservoir were primarily via macrophyte absorption,particulate substance sedimentation,and prolonged water residence time.Consequently,the phytoplankton biomass(Chl-a) in the reservoir decreased(from 48.0 to 25.2 μg/L) and water transparency improved,due to the decreased P level and transformation of the phytoplankton group into simple structures with good ecological status.Therefore,the combination of embedded reservoir and constructed wetland ecosystem can be used successfully to protect surface water.The results will be advantageous to groups seeking to preserve drinking water sources.     

Development of methods for establishing nutrient criteria in lakes and reservoirs: A review

Nutrient criteria provide a scientific foundation for the comprehensive evaluation, prevention,control and management of water eutrophication. In this review, the literature was examined to systematically evaluate the benefits, drawbacks, and applications of statistical analysis,paleolimnological reconstruction, stressor-response model, and model inference approaches for nutrient criteria determination. The developments and challenges in the determination of nutrient criteria in lakes and reservoirs are presented. Reference lakes can reflect the original states of lakes, but reference sites are often unavailable. Using the paleolimnological reconstruction method, it is often difficult to reconstruct the historical nutrient conditions of shallow lakes in which the sediments are easily disturbed. The model inference approach requires sufficient data to identify the appropriate equations and characterize a waterbody or group of waterbodies, thereby increasing the difficulty of establishing nutrient criteria. The stressor-response model is a potential development direction for nutrient criteria determination, and the mechanisms of stressor-response models should be studied further. Based on studies of the relationships among water ecological criteria, eutrophication, nutrient criteria and plankton, methods for determining nutrient criteria should be closely integrated with water management requirements.     

Technologies for pollutant removal and resource recovery from blackwater: a review

● Blackwater is the main source of organics and nutrients in domestic wastewater. ● Various treatment methods can be applied for resource recovery from blackwater. ● Blackwater treatment systems of high integration and efficiency are the future trend. ● More research is needed for the practical use of blackwater treatment systems. Blackwater (BW), consisting of feces, urine, flushing water and toilet paper, makes up an important portion of domestic wastewater. The improper disposal of BW may lead to environmental pollution and disease transmission, threatening the sustainable development of the world. Rich in nutrients and organic matter, BW could be treated for resource recovery and reuse through various approaches. Aimed at providing guidance for the future development of BW treatment and resource recovery, this paper presented a literature review of BWs produced in different countries and types of toilets, including their physiochemical characteristics, and current treatment and resource recovery strategies. The degradation and utilization of carbon (C), nitrogen (N) and phosphorus (P) within BW are underlined. The performance of different systems was classified and summarized. Among all the treating systems, biological and ecological systems have been long and widely applied for BW treatment, showing their universality and operability in nutrients and energy recovery, but they are either slow or ineffective in removal of some refractory pollutants. Novel processes, especially advanced oxidation processes (AOPs), are becoming increasingly extensively studied in BW treatment because of their high efficiency, especially for the removal of micropollutants and pathogens. This review could serve as an instructive guidance for the design and optimization of BW treatment technologies, aiming to help in the fulfilment of sustainable human excreta management.     

Application of constructed wetlands for wastewater treatment in tropical and subtropical regions (2000–2013)

Constructed wetlands (CWs) have been successfully used for treating various wastewaters for decades and have been identified as a sustainable wastewater management option for developing countries. With the goal of promoting sustainable engineered systems that support human well-being but are also compatible with sustaining natural (environmental) systems, the application of CWs has become more relevant. Such application is especially significant for developing countries with tropical climates, which are very conducive to higher biological activity and productivity, resulting in higher treatment efficiencies compared to those in temperate climates. This paper therefore highlights the practice, applications, and research of treatment wetlands under tropical and subtropical conditions since 2000. In the present review, removal of biochemical oxygen demand (BOD) and total suspended solid (TSS) was shown to be very efficient and consistent across all types of treatment wetlands. Hybrid systems appeared more efficient in the removal of total suspended solid (TSS) (91.3%), chemical oxygen demand (COD) (84.3%), and nitrogen (i.e., 80.7% for ammonium (NH)₄-N, 80.8% for nitrate (NO)₃-N, and 75.4% for total nitrogen (TN)) as compared to other wetland systems. Vertical subsurface flow (VSSF) CWs removed TSS (84.9%), BOD (87.6%), and nitrogen (i.e., 66.2% for NH₄-N, 73.3% for NO₃-N, and 53.3% for TN) more efficiently than horizontal subsurface flow (HSSF) CWs, while HSSF CWs (69.8%) showed better total phosphorus (TP) removal compared to VSSF CWs (60.1%). Floating treatment wetlands (FTWs) showed comparable removal efficiencies for BOD (70.7%), NH₄-N (63.6%), and TP (44.8%) to free water surface (FWS) CW systems.     

Application of constructed wetlands for wastewater treatment in tropical and subtropical regions (2000-2013)

Constructed wetlands(CWs) have been successfully used for treating various wastewaters for decades and have been identified as a sustainable wastewater management option for developing countries. With the goal of promoting sustainable engineered systems that support human well-being but are also compatible with sustaining natural(environmental)systems, the application of CWs has become more relevant. Such application is especially significant for developing countries with tropical climates, which are very conducive to higher biological activity and productivity, resulting in higher treatment efficiencies compared to those in temperate climates. This paper therefore highlights the practice,applications, and research of treatment wetlands under tropical and subtropical conditions since 2000. In the present review, removal of biochemical oxygen demand(BOD) and total suspended solid(TSS) was shown to be very efficient and consistent across all types of treatment wetlands. Hybrid systems appeared more efficient in the removal of total suspended solid(TSS)(91.3%), chemical oxygen demand(COD)(84.3%), and nitrogen(i.e.,80.7% for ammonium(NH)4-N, 80.8% for nitrate(NO)3-N, and 75.4% for total nitrogen(TN))as compared to other wetland systems. Vertical subsurface flow(VSSF) CWs removed TSS(84.9%), BOD(87.6%), and nitrogen(i.e., 66.2% for NH4-N, 73.3% for NO3-N, and 53.3% for TN)more efficiently than horizontal subsurface flow(HSSF) CWs, while HSSF CWs(69.8%)showed better total phosphorus(TP) removal compared to VSSF CWs(60.1%). Floating treatment wetlands(FTWs) showed comparable removal efficiencies for BOD(70.7%),NH4-N(63.6%), and TP(44.8%) to free water surface(FWS) CW systems.     

An Approach for Estimating Soil Carbon Using the National Nutrient Loss Database

Agricultural lands have the potential to contribute to greenhouse gas mitigation by sequestering organic carbon within the soil. Credible and consistent estimates will be necessary to design programs and policies to encourage management practices that increase carbon sequestration. Because a nationwide survey of soil carbon by the wide range of natural resources and management conditions of the United States is prohibitively expensive, a simulation modeling approach must be used. The National Nutrient Loss Database (NNLD) is a modeling and database system designed and built jointly by the USDA– Natural Resources Conservation Service (NRCS) and Texas A&M University to provide science-based inferences on environmental impacts from changes in agricultural management practices and programs at the regional and national level. Currently, the NNLD simulates 16 crops and covers 1.35 × 10⁸ ha. For estimating soil carbon sequestration, the database will be populated with 1.5 × 10⁶ field-level model runs using the EPIC (Environmental Policy Impact Calculator) model, which includes newly incorporated carbon equations consistent with those in the Century model. Each run will represent a unique situation defined by state, crop, climate, soil, irrigation type, conservation practice, tillage system, and nutrient management treatment (nutrient rate, application frequency, application timing, and manure category). Results are to be assigned to specific National Resource Inventory points (NRI) to simulate regional and national baselines. In this article we present the modeling approach and discuss the strengths and limitations. Published online     

Eutrophication of Buttermilk Bay,a cape cod coastal embayment: Concentrations of nutrients and watershed nutrient budgets

Nutrient concentrations in Buttermilk Bay, a coastal embayment on the northern end of Buzzards Bay, MA, are higher in the nearshore where salinities are lower. This pattern suggests that freshwater sources may contribute significantly to nutrient inputs into Buttermilk Bay. To evaluate the relative importance of the various sources we estimated inputs of nutrients by each major source into the watershed and into the bay itself. Septic systems contributed about 40% of the nitrogen and phosphorus entering the watershed, with precipitation and fertilizer use adding the remainder. Groundwater transported over 85% of the nitrogen and 75% of the phosphorus entering the bay. Most nutrients entering the watershed failed to reach the bay; uptake by forests, soils, denitrification, and adsorption intercepted two-thirds of the nitrogen and nine-tenths of the phosphorus that entered the watershed. The nutrients that did reach the bay most likely originated from subsoil injections into groundwater by septic tanks, plus some leaching of fertilizers.Buttermilk Bay water has relatively low nutrient concentrations, probably because of uptake of nutrients by macrophytes and because of relatively rapid tidal flushing. Annual budgets of nutrients entering the watershed showed a low nitrogen-to-phosphorus ratio of 6, but passage of nutrients through the watershed raised N/P to 23, probably because of adsorption of PO₄ during transit. The N/P ratio of water that leaves the watershed and presumably enters the bay is probably high enough to maintain active growth of nitrogenlimited coastal producers. There is a seasonal shift in N/P in the water column of Buttermilk Bay. N/P exceeded the 161 Redfield ratio during midwinter; the remainder of the year N/P fell below 161. This suggests that annual budgets do not provide sufficiently detailed data with which to interpret nutrient-limitation of producers. Further, some idea of water turnover is also needed to evaluate impact of loading rates. Urbanization of watersheds seems to increase loadings to nearshore environments, and to shift the nutrient loadings delivered to coastal waters to relatively high N-to-P ratios, potentially stimulating growth of nitrogen-limited primary producers.     

基于NLM的三峡重庆库区面源污染负荷研究

随机性、模糊性、不确定性很强的面污染源是水环境污染中最主要的污染源。面源污染负荷的准确估算是研究和治理面源污染的基础。现在的面源污染数字模型大多数建立于DEM之上，高成本的DEM限制着这类模型的发展。新兴模型——NLM以面源污染发生机理完善而著称。借助于NLM，以三峡重庆库区为例研究分析面源污染的机理，面源污染负荷随时间的变化以及面源负荷受各因素的影响程度等。从硝化、反硝化、矿化、吸附等作用过程中更深层地剖析了面源污染行为；掌握了面源污染物TP、NH3-N、NO3-N的随时间的变化规律及降雨量、土壤有机成分、土壤气温、总辐照等因子对各污染物负荷的影响及相互关系。总之，NLM为开展面源污染负荷及影响因素的研究提供了科学依据。     

Nutrient-limited toxin production and the dynamics of two phytoplankton in culture media: A mathematical model

In this paper we have proposed and analyzed a simple mathematical model consisting of four variables, viz., nutrient concentration, toxin producing phytoplankton (TPP), non-toxic phytoplankton (NTP), and toxin concentration. Limitation in the concentration of the extracellular nutrient has been incorporated as an environmental stress condition for the plankton population, and the liberation of toxic chemicals has been described by a monotonic function of extracellular nutrient. The model is analyzed and simulated to reproduce the experimental findings of Graneli and Johansson [Graneli, E., Johansson, N., 2003. Increase in the production of allelopathic Prymnesium parvum cells grown under N- or P-deficient conditions. Harmful Algae 2, 135–145]. The robustness of the numerical experiments are tested by a formal parameter sensitivity analysis. As the first theoretical model consistent with the experiment of Graneli and Johansson (2003), our results demonstrate that, when nutrient-deficient conditions are favorable for the TPP population to release toxic chemicals, the TPP species control the bloom of other phytoplankton species which are non-toxic. Consistent with the observations made by Graneli and Johansson (2003), our model overcomes the limitation of not incorporating the effect of nutrient-limited toxic production in several other models developed on plankton dynamics.     

光照和营养盐对DBP在海河河口水中生物降解的影响

采集渤海海河河口水,在实验室受控条件下,研究了营养盐和光照条件对邻苯二甲酸二丁酯(DBP)生物降解的影响。实验结果表明:DBP在海河河口水中的生物降解符合一级动力学,微生物降解占总去除率的99%左右,微生物降解是DBP降解的主要途径。高营养水平时,DBP在光照、光暗条件下的生物降解速率常数分别为0.32d-1和0.41d-1;低营养水平时,DBP在光照、光暗条件下的生物降解速率常数分别为0.17d-1和0.20d-1。高营养条件下较高的微生物总量使DBP的生物降解速率明显大于相对低营养条件下的降解速率;在相同的营养条件下,光照能够改变水体中藻、菌的微生态结构,从而延迟DBP的降解。