Dynamics of the behaviour of a vertical wetland (French system) operating in warm-climate conditions, evaluated by means of variables continuously measured in situ

The sewage treatment system in this study was operated with only the first stage of a French system of vertical wetlands, composed of two units in parallel and running with an extended feeding cycle (7 days). This research sought to evaluate and relate continuous variables measured in situ (dissolved oxygen (DO), pH and redox potential) throughout the feeding cycle, with measurements at distinct heights along the filter vertical profile. Additionally, the influence of the surface organic sludge deposit was investigated. A close link between the hydraulic behaviour and the effluent quality was verified, with both being related to the batch volume and the instantaneous hydraulic loading rate. The drop in DO as the feed days progressed could be related to the loss of hydraulic conductivity. A thicker sludge layer decreased the aeration capacity of the filter. The effluent was observed to be aerated when percolating through the medium. DO and pH data suggested that nitrification varied along the filter depth, the batch duration and the feed cycle. The monitored parameters may be indicative of the behaviour of other parameters.

Physical Quality Indicators of an Oxisol Under Grass in the Agreste Region of Paraiba, Brazil

The aim of this study was to evaluate the influence of different grass cultivars on physical attributes of an Oxisol in the Agreste region of Paraíba. The experiment was set up in 2005 in experimental areas of the Center of Agricultural Sciences of the Federal University of Paraíba, Areia-PB. The experimental design adopted was that of randomized complete blocks (RCB) with 5 treatments and 4 replications, in experimental plots of 50 m2. The treatments were the following: I. Brachiaria decumbens Stapf., II. Brachiaria brizantha, III. Brachiaria humidicola (Rendle) Schweickvr., IV. Brachiaria brizantha cv. MG5-Vitória and V. Brachiaria ruziziensis. In October 2018 samples of soil with disturbed and undisturbed structure were collected at the center of each experimental plot in the depth of 0.0-0.10 m for the determination of the following variables: soil porosity (total, macro and micro), bulk density, compaction degree, saturated hydraulic conductivity, field capacity, permanent wilting point, available water content, soil aeration capacity, clay dispersed in water, flocculation degree and aggregate stability index. The analysis of variance was performed and the means were compared by Tukey’s tests, principal component analysis and Pearson’s correlation analysis (p < 0.05). It is concluded that after the 13-year period, Brachiaria brizantha promoted improvements to the field capacity of the Oxisol. The other attributes were not physically altered. Main component analysis showed that the correlation values were more significant for the Brachiaria brizantha component. Pearson’s correlation was significant between field capacity and soil aeration capacity.

Oxisol physical quality with application of landfill leachate

The organic carbon present in the landfill leachate (LL) can improve the physical quality of the soil when applied in agricultural areas, minimizing the problem of disposal of this waste. The objective of this work was to evaluate the effect of the application of different doses of LL on the physical quality of the Red Latosol (Oxisol) after five years of applications. The treatment consisted of applications of LL in doses of 32, 65, 98 and 130 m3 ha-1 crop-1 and the treatment that receives mineral fertilizer. The physical quality of the soil was evaluated in soil samples collected in the layers 0.00-0.10 and 0.10-0.20 m, through the analysis of stability and diameter of the aggregates, soil density, total aeration capacity, field capacity and available water content. After five years of application of LL, at doses of 65, 98 and 130 m3 ha-1 crop-1 have promoted a linear increase of the aggregates with diameter greater than 2.00 mm, of the weighted average and geometric diameters and of the soil density, with a consequent reduction of the ratio between macro and micropores and the aeration capacity of the layers 0.00-0.10 and 0.10-0.20 m. After five years of these applications, the soils that received the dose of 32 m3 ha-1 crop-1 presented the best physical quality in relation to the other doses, since this dose did not promote an increase of the aggregates larger than 2 mm in the superficial layer (0.00-0.10 m) and was the dose with lower effect in the reduction of aeration of the soil, in relation to the others (65, 98 and 130 m3 ha-1 season-1) in the layers 0.00-0, 10 and 0.10 - 0.20 m.

Environmental Sustainability through Recycling Incineration Bottom Ash for the Production of Autoclaved Aerated Concrete

Municipal solid waste incineration bottom ash (IBA) has great potential to be utilized for civil engineering applications. This paper is to investigate the characteristic of gas generation from IBA and to study the potential of IBA as aerating agent to replace costly aluminum powder and as silica source to partially replace silica flour/fly ash in the production of autoclaved aerated concrete (AAC). Results show the aeration capacity of IBA used in this study is about 1% that of pure aluminum powder by mass. Finer particles, higher alkali molarity, and higher reaction temperature encourage the reaction and more gas is generated per gram of IBA. Type of alkaline solution does not seem to be an important factor for gas generation from IBA. Several exemplary lightweight mortars and AACs were produced by incorporating IBA as aerating agent. It is highly plausible IBA can be used as aerating agent to replace pure aluminum powder in the production of normal aerated concrete. IBA-AACs with density ranging from 600 to 800 kg/m3 were successfully synthesized by using IBA as aerating agent. For a given density, the compressive strength of IBA-AAC is higher than that of AAC due to the formation of more uniform pore structure with smaller pore size in IBA-AAC.

Assessment of soil physical health and productivity of Kharkhoda and Gohana blocks of Sonipat district (Haryana), India

In order to assess soil health of Kharkhoda and Gohana blocks of Sonipat district (a part of western Yamuna canal irrigated region), important parameters namely pH, electrical conductivity (EC), texture, bulk density (BD), saturated hydraulic conductivity (HC), soil organic carbon (OC), available water retension capacity (AWRC) and non capillary pores (NCP) were measured by collecting undisturbed soil samples in nearly 66 villages. Soil physical rating index (PI) method was used to compute PI which was an indicator of soil physical health of thatregion. Results revealed that in Gohana and Kharkhoda blocks, nearly 90% area had pH <8.0 and EC>4 dS m-1, which indicated that soils were saline. Prediction maps of soil BD showed that 75% of the total area in 15-30 cm soil layer had BD above >1.6 mg m-3, which indicated the presence of hard pan in subsurface. HC data of subsurface layer also showed that 60% of the area had values<0.5 cm hr-1 which reconfirmed the presence of hard pan. For both surface as well as subsurface soil layers, mostly AWC was >10% which indicated adequate water retention capacity of these soils. However 85% of subsurface had poor soil aeration capacity as indicated NCP range < 10 %. Prediction map of PI for subsurface layer showed that majority of area had PI<0.4 which indicated that expected yield of the crop cannot be more than 70% of the potential yield even under normal or higher levels of fertilizer and water inputs.

Aeration performance of hydrodynamic flow regulators

Hydrodynamic flow regulators are used in environmental engineering as a replacement for traditional flow throttling devices. They are extremely efficient, reliable and free from the common disadvantages of traditional devices. Recent research by the authors indicated that the atomization of a liquid by hydrodynamic flow regulators accelerates oxygenation and may be used for improving the quality of wastewater and stormwater. To date, an evaluation of the aeration capacity of a hydrodynamic flow regulator at the pilot scale or in a practical situation has not been presented in the literature. This study presents the experimental results of oxygen absorption tests for conventional and modified cylindrical hydrodynamic flow regulators (patent pending). These devices were tested in a closed-circuit experimental setup at the semi-commercial scale. The aeration efficiency of hydrodynamic flow regulators was assessed by means of the overall standard oxygen transfer coefficient (KLa(20), h−1) and standard oxygen transfer rate (SOTR, gO2/h) for a wide range of tested configurations. The effect of flow rate and discharge mode on the aeration capacity of flow regulators was investigated. The values of KLa(20) for cylindrical hydrodynamic flow regulators obtained in the experiments were between 2.62 and 15.57 h−1 while SOTR values ranged from 53 to 316 gO2/h. The modified discharge mode with two active outlets allowed for an increase in aeration efficiency of up to 15% compared to conventional designs.

SHARON process evaluated for improved wastewater treatment plant nitrogen effluent quality

New stricter nitrogen effluent standards and increasing influent loads require existing wastewater treatment plans (WWTPs) to extend or optimize. At WWTPs with limited aeration capacity, limited denitrification capacity or shortage of aerobic sludge age, implementation of SHARON to improve nitrogen effluent quality can be a solution. SHARON is a compact, sustainable and cost-effective biological process for treatment of nitrogen-rich rejection waters. At WWTP Rotterdam-Dokhaven and WWTP Utrecht a SHARON has been in operation for several years. For both WWTPs the effect of SHARON on the nitrogen effluent quality has been evaluated. WWTP Rotterdam-Dokhaven has limited aeration capacity. By implementation of SHARON, the ammonia load of the effluent was reduced by 50%. WWTP Utrecht had limited denitrification capacity. The implementation of SHARON improved the effluent nitrate load by 40%. The overall TN removal efficiency increased from 65% to over 75% and strict nitrogen effluents standards (TN = 10 mg N/l) could be reached. Through modelling and supported by full scale practice it has been shown that by implementation of SHARON in combination with enhanced influent pre-treatment, the aerobic sludge age can be extended to maintain total nitrogen removal at lower temperatures.

Comparison between Peat and Fresh Rice Hulls: Hydraulic and Chemical Characteristics

One of the most widely used substrates in nursery production is peat, which is used as plain substrate or mixed with other media. Peat use is problematic, primarily because of the high price and the environmental implications connected with its extraction and disposal. For these reasons, the exploitation will be restricted in the future in both Europe and America. Thus, researchers are under pressure to find alternative substrates that can be used in an inexpensive and environmentally friendly way. Although aged, carbonized and composted rice hulls have been used to a limited extent, more studies are needed to characterize fresh rice hulls as a growing medium. This research was aimed at characterizing fresh hulls after being ground in different particle sizes, and comparing them with peat. Ground hulls were separated into four fractions (6-, 4-, 2-, and 1-mm diameter), which were characterized for pH, EC, CEC, organic matter, and total nitrogen content. The water retention curve was also estimated and the following hydraulic characteristics were measured and compared: TP, CC, AFP, EAW, and WBC. As expected, pH, N, and C content and CEC did not differ among rice hull fractions, while EC showed a slight but constant increase when particle dimensions decreased. Compared to peat, the TP of rice hulls was smaller independently from particle dimensions, but AFP was 19.5%, 44,1%, 114.2%, and 115.8% higher for 1-, 2-, 4-, and 6-mm particles, respectively, indicating a very good aeration capacity. EAW and WBC were higher only in 1- and 2-mm particles. A further experiment aimed at comparing the behavior of transplants in rice hulls (6 mm) and peat showed that tomato plantlets grew slower in the former, although transplants were of good, marketable quality.