Treating acid mine drainage with decomposed organic soil: Implications for peatland rewetting.

Acidification and salinisation of groundwater and surface water bodies are worldwide problems in post-mining landscapes due to acid mine drainage (AMD). In this study, we hypothesised that highly decomposed peat offers a suitable substrate for mitigating AMD pollution of water bodies and that hydraulic load affects the removal efficiency of iron and sulphate. A lysimeter experiment was conducted mimicking peatland rewetting to quantify iron and sulphate removal and pH changes at different loading rates. The low initial pH of 4 rose to 6 and electrical conductivity declined by up to 47%. The initially high concentrations of iron (>250 mg/L) and sulphate (>770 mg/L) declined by, on average, 87 and 78%, respectively. The removal efficiency of sulphate was negatively correlated with either the hydraulic or the sulphate load, respectively, i. e. the lower the hydraulic load, the higher the removal efficiency of sulphate. However, the removal of iron was not explained by the load. The results imply that desulphurication and thus subsequent precipitation of iron sulphides was the main removal process and that peatland rewetting is an effective measure to mitigate AMD pollution of freshwater systems. For the heavily AMD-polluted studied section of the River Spree, we estimated by combining experimental with field data that a sulphate load reduction of the river by about 20% (36,827 tons/yr) will occur if all peatlands in the sub-catchment (6067 ha; 6.7% of the total area) are rewetted. Future investigations must show if the pollutant removal is declining over time in decomposed peat layers due to acidification and/or lack of bioavailable carbon and how the rewetting of peatland with AMD will affect the restoration of their ecosystem functioning in the long term.

Control of Hydraulic Load on Bacterioplankton Diversity in Cascade Hydropower Reservoirs, Southwest China.

Hydroelectric reservoirs are highly regulated ecosystems, where the understanding on bacterioplankton has been very limited so far. In view of significant changes in river hydrological conditions by dam construction, hydraulic load (i.e., the ratio of mean water depth to water retention time) was assumed to control bacterioplankton diversity in cascading hydropower reservoirs. To evaluate this hypothesis, we investigated bacterioplankton composition and diversity using high-throughput sequencing and related environmental variables in eleven reservoirs on the Wujiang River, Southwest China. Our results showed a decrease of bacterioplankton diversity index with an increase of reservoir hydraulic load. This is because hydraulic load governs dissolved oxygen variation in the water column, which is a key factor shaping bacterioplankton composition in these hydroelectric reservoirs. In contrast, bacterioplankton abundance was mainly affected by nutrient-related environmental factors. Therefore, from a hydrological perspective, hydraulic load is a decisive factor for the bacterioplankton diversity in the hydroelectric reservoirs. This study can improve the understanding of reservoir bacterial ecology, and the empirical relationship between hydraulic load and bacterioplankton diversity index will help to quantitatively evaluate ecological effects of river damming.

Enhancement of nitrogen removal by a modular design of vertical flow constructed wetlands with a plant carbon source: Optimization of carbon dosage for nitrogen removal, practicability evaluation and strategy exploration for water quality control.

The requirement of artificial aeration for increasing nitrogen removal in vertical flow constructed wetlands (VFCWs) brings extra energy consumption and complex maintenance. The feasibility of a modular design to replace artificial aeration for partially saturated VFCWs with palm bark as a carbon source (PSVFCW-pb) to achieve water quality control, especially nitrogen removal was evaluated. The PSVFCW-pb with a spatially separate structure and perforated peripheries for better oxygen diffusion had a promising total nitrogen removal (e.g., 66.4% at a dosage of 1.435 g/L of palm bark pretreated at 120 °C for 40 min) without additional aeration, while organic carbon removal was nearly unaffected. An appropriate increase of the palm bark dosage (≤1.435 g/L) resulted in higher nitrogen removal; however, a more palm bark (1.875 g/L) could not further increase nitrogen removal but caused color pollution. In addition, the removal of nitrogen by the modularized PSVFCW-pb was more sensitive to the ambient temperature than the removal of organic carbon and phosphorus, and the higher temperature was preferable. Notably, the more attractive property of the modular design is its great potential to improve nitrogen removal by conveniently altering the number and/or scale of oxic and oxygen-free modules. Finally, the relationships between the hydraulic load and inflow concentration were explored, by which the suitable hydraulic load could be flexibly adjusted based on real-time water quality to meet the specified surface water quality criteria in different seasons. This study provides a reliable CW design for controlling nutrient pollution in surface waters.

Research on removal of fluoroquinolones in rural domestic wastewater by vertical flow constructed wetlands under different hydraulic loads.

Antibiotics had attracted more and more attention in recent years due to their harmfulness. Fluoroquinolones (FQs), one class of antibiotics widely used in human and veterinary medicine, were found in various water bodies in China. Therefore, in order to found an efficient method for removing FQs in rural domestic wastewater and optimize the process parameters, ceramsite and soil were applied in vertical flow constructed wetlands (VFCWs) to study the effects of different hydraulic loads and different substrates on the removal of FQs and conventional pollutants. The results showed the VFCW-D filled with 45 cm soil layer and 15 cm ceramasite layer had the highest removal efficiency of conventional pollutants and FQs under low hydraulic load. Nevertheless, the removal efficiency of conventional pollutants was significantly declined for the VFCWs which contained soil substrates under high hydraulic load due to the soil pores were clogged by the accumulation of organic matter. Finally, VFCW-A filled with 60 cm ceramasite layer revealed good ability to remove conventional pollutants and FQs under high hydraulic load. Deinococcus played a vital role here due to its excellent removal effect on conventional pollutants. The microbial composition in the substrate changed greatly after adding antibiotics under high hydraulic load. Devosia, Pseudorhodoferax, Cellvibrio, Bosea, Caulobacter, Acinetobacter, Zoogloea, Arcobacter, Dechloromonas, Flavobacterium, Nakamurella, Chloroplast, Clostridium_sensu_stricto_1, Pelosinus, UTCFX1 and Hypnocyclicus became the new dominated genera and were essential to remove pollutants. In summary, VFCW was an effective system to remove fluoroquinolones in rural domestic wastewater.

Analysis on common problems of the wastewater treatment industry in urban China.

The wastewater treatment industry in urban China generally faces certain common problems. To provide a comprehensive analysis on common problems of the wastewater treatment industry, survey data from 467 wastewater treatment plants (WWTPs) and field investigation reports of 38 WWTPs were analyzed. The research results showed that, the common problems of the wastewater treatment industry are mainly concentrated in WWTPs and the drainage system. The length of per capita drainage networks is insufficient, only 0.85 m; approximately 63.17% WWTPs have hydraulic load rates (HLRs) are greater than 80%, and the ratio of water quality between the design value and actual value is approximately 0.7; and there is still a considerable gap in construction of wastewater treatment facilities compared to those in developed countries. These are still major common problems perplexing the wastewater treatment industry in urban China. In this study, the common problems that hinder improving the operation efficiency of WWTPs were investigated, the causes of the discrepancy were analyzed, and three countermeasures, such as refinement design, optimization facilities and reasonable process control were jointly explored to solve them. This study may provide valuable insights and methods for the wastewater treatment industry to effectively address the discrepancy between the design and actual operation of WWTPs.

A high-sensitivity hydraulic load cell for small kitchen appliances.

In this paper we present a hydraulic load cell made from hydroformed metallic bellows. The load cell was designed for a small kitchen appliance with the weighing function integrated into the composite control and protection of the appliance. It is a simple, low-cost solution with small dimensions and represents an alternative to the existing hydraulic load cells in industrial use. A good non-linearity and a small hysteresis were achieved. The influence of temperature leads to an error of 7.5%, which can be compensated for by software to meet the requirements of the target application.

Changes in bacteria composition and efficiency of constructed wetlands under sustained overloads: A modeling experiment.

The average organic and hydraulic loads that Constructed Wetlands (CWs) receive are key parameters for their adequate long-term functioning. However, over their lifespan they will inevitably be subject to either episodic or sustained overloadings. Despite that the consequences of sustained overloading are well known (e.g., clogging), the threshold of overloads that these systems can tolerate is difficult to determine. Moreover, the mechanisms that might sustain the buffering capacity (i.e., the reduction of peaks in nutrient load) during overloads are not well understood. The aim of this work is to evaluate the effect of sudden but sustained organic and hydraulic overloads on the general functioning of CWs. To that end, the mathematical model BIO_PORE was used to simulate five different scenarios, based on the features and operation conditions of a pilot CW system: a control simulation representing the average loads; 2 simulations representing +10% and +30% sustained organic overloads; one simulation representing a sustained +30% hydraulic overload; and one simulation with sustained organic and hydraulic overloads of +15% each. Different model outputs (e.g., total bacterial biomass and its spatial distribution, effluent concentrations) were compared among different simulations to evaluate the effects of such operation changes. Results reveal that overloads determine a temporary decrease in removal efficiency before microbial biomass adapts to the new conditions and COD removal efficiency is recovered. Increasing organic overloads cause stronger temporary decreases in COD removal efficiency compared to increasing hydraulic loads. The pace at which clogging develops increases by 10% for each 10% increase on the organic load.

Nonlinear robust dual-loop control for electro-hydraulic load simulator.

This paper investigates on the high performance torque control of electro-hydraulic load simulator (EHLS). In order to suppress actuator's motion disturbance, a nonlinear robust dual-loop control scheme is developed, which consists of a open-loop nonlinear velocity feed-forward compensator and a closed-loop nonlinear deterministic robust torque controller. The main function of the open-loop compensator is to decouple actuator's active motion disturbance, whereas the torque loop controller aims at guaranteeing the dynamics performance of tracking torque reference. Besides actuator's motion disturbance, both the nonlinearity characteristics and friction problem of the EHLS system are taken into consideration in this paper. The effectiveness of the developed method are verified through comparative co-simulations and experiments.

Tomato (Lycopersicon esculentum P. Miller) compression due to "K" wood box closing / Compressão de tomate (Lycopersicon esculentum P. Miller) em função do fechamento da caixa de madeira tipo "K"

Wood boxes kind "k" are the most used in table tomato (Lycopersicon esculentum P. Miller) commercialization in Brazil. Due to the fruit accommodation process that occurs during the transport from the production place to the commercialization point, producers fill tomato boxes a little bit over its physical capacity, and they close it with wood strips fixed with nails. In order to prevent strips from cracking, it is common to keep them inside water before using, to increase flexibility. When boxes are opened, many fruits are cracked or kneaded in a significant part of their total area, and normally they are thrown away. The purpose of this paper was to quantify the compression tomato fruits are exposed to in consequence of the "k" box fill / closing system. For this study a special instrumented box was constructed with a scales plate located at the bottom, with a hydraulic load cell instrumented in the box. This instrument was then used to study the compression of fruits as the box is filled and the compression increase caused by the addition of its wooden lid. The "k" box closing system caused an initial compression increase 3.5 times the compression of the open tomato box, and during time as the fruits are substantially deformed. This compression was reduced two about two times de initial reference value. The consequence of this observed fruit compression is compatible with the fruit deformations and even cracks observed in the market, which are known to be relevant post harvest losses causes in the Brazilian tomato handling industry.

Caixas de madeira do tipo "K" são as mais utilizadas na comercialização de tomate (Lycopersicon esculentum P. Miller) de mesa no Brasil. Em razão do processo de acomodação dos frutos que ocorre durante o transporte desde o local de produção até o local de comercialização, os produtores enchem a caixa de tomate um pouco acima de sua capacidade física e a fecham com ripas de madeira e pregos. Para evitar que as ripas rachem, é comum mantê-las imersas em água antes do fechamento, para que fiquem mais flexíveis. Quando as embalagens são abertas, muitos frutos estão rachados ou amassados em parte significativa de sua área e, normalmente, são descartados. Para este estudo, construiu-se uma embalagem cujo fundo é uma balança, com uma célula de carga hidráulica acomodada no fundo da caixa. Desse modo, a pressão que os frutos sofreram no interior da caixa com e sem o fechamento da tampa foi registrada ao longo do tempo, com auxílio de um tubo manométrico. O fechamento da caixa aumentou, inicialmente, em 3,5 vezes a compressão e depois, com a deformação plástica dos frutos, a compressão diminuiu para cerca de duas vezes em relação à compressão observada na caixa aberta. Portanto, as pressões observadas no fechamento da caixa comprimem os frutos de tomate, causando amassamento e até mesmo rachaduras. Estas injúrias têm sido observadas frequentemente na pós-colheita deste e outros produtos e são causas primárias de perdas consideráveis.