Revisiting Gas to Solids Ratio for Activated Sludge Clarification by Electrolytic Hydrogen Bubbles: Theoretical and Experimental Evaluations

Molecular hydrogen (H2), as the green energy carrier from water electrolysis, can be utilized for separation of suspended micro-particles as electroflotation (EF). This study provides practical guidelines for the gas to solids (G/S) ratio as the governing parameter in EF, based on theoretical estimations and experiments for clarification of activated sludge. The G/S ratio in EF was controlled linearly by current density (j), under quasi-consistent current efficiency (at j > 8 mA/cm2) for H2 (~1) and O2 (~0.4) bubble generations on Ti cathode and IrTaOx anode, respectively. Based on the measured sizes of bubbles (approximated to 35 µm) and biological flocs (discretized to mean sizes of 22.5, 40, 60, 135, and 150 µm), batch flotation experiments estimated the maximum collision-attachment efficiency of 0.057. The rise velocities of floc-bubble aggregate were computed to derive the limiting G/S ratio to overcome the given influent hydraulic loading. Consequently, the estimates (5.23 × 10−4 and 5.92 × 10−4 at hydraulic loading of 0.87 and 1.73 cm/min, respectively) were compatible with the continuous EF experiments.

Treatment of seawater salinity sewage with intermittent sand bioreactors

In water stressed areas, flush toilets using fresh water are unsustainable. This paper explores the ability of intermittent sand bioreactors (ISBs) to treat seawater salinity septic tank effluent for on-site wastewater treatment in coastal regions. Two ISB designs, sand only and layered sand and gravel, are compared for treatment efficacy. Six columns of each design were constructed in the laboratory and dosed four times per day, for a total hydraulic loading rate of 4 cm/day, with artificial seawater salinity septic tank effluent over 21 months. Average TOC and ammonia removal for both designs averaged >90% and >96%, respectively. No statistically significant difference existed in the percent removal or effluent concentrations between the two designs. Half of the columns of each design produced effluent with >4 mg/L ammonia at least once during the study, resulting in discontinuation of wastewater application for seven weeks. This resting approach resulted in effective treatment for up to 9 months (limited by the end of the study). The results indicate that both ISB designs can treat artificial seawater salinity septic tank effluent, but that an additional 1/3 capacity is needed to maintain a consistent hydraulic loading rate while accounting for resting ISBs when treatment efficacy declines.

Optimization of Biofilter Size for Aquaponics Using Genetic Algorithm

Unlike a media-filled aquaponic system, the nutrient film technique (NFT) and deep water culture (DWC) require the installation of an external biofilter to provide sufficient area for nitrifying bacteria colonization, which is essential for the conversion of toxic ammonia from fish waste into nitrate that is easily assimilated by plants. Given the importance of biofilters, it is imperative to properly design this tank to effectively support the nitrification process. Several factors need to be considered for the biofilter design. Thus, an optimization algorithm can be used to obtain combinations of the design parameters. The genetic algorithm (GA) is a heuristic solution search or optimization technique based on the Darwinian principle of genetic selection. The main goal of this study was to obtain the optimal biofilter size for a given fishpond volume and the amount of ammonia to be treated. The conversion coefficient in the Michaelis–Menten equation was used as the fitness function in this study. The parameters optimized using GA include the hydraulic loading rate, height of the biofilter, and predicted ammonia concentration. For the given assumption of a 60 kg feed introduced to the system and a 1500 L fishpond, the hydraulic loading rate, biofilter height, and final concentration of ammonia were 0.17437 m, 0.58585 m, and 0.01026 ppm, respectively. Using the values obtained from running the GA, the optimum biofilter volume for the system was 0.4608 m3, whereas the water flow rate was 0.03 L/min. For recommendations, multiple objective GAs can be used to add cost-related variables in the optimization because they have not yet been considered in the computation.

Estimating the Importance of Hydrologic Conditions on Nutrient Retention and Plant Richness in a Wetlaculture Mesocosm Experiment in a Former Lake Erie Basin Swamp

The western basin of Lake Erie, the shallowest of the Laurentian Great Lakes in North America, is now plagued by harmful algal blooms annually due to nutrient discharges primarily from its basin. Water quality was impacted so significantly by toxic cyanobacteria in 2014 that the city of Toledo’s water supply was shut off, affecting hundreds of thousands of residents. A new agricultural land management approach, ‘wetlaculture (=wetland + agriculture)’, has a goal of reducing the need for fertilizer applications while preventing fluxes of nutrients to downstream aquatic ecosystems. A wetlaculture mesocosm experiment was set up on agricultural land near Defiance, Ohio, on the northwestern edge of the former ‘Great Black Swamp’. The mesocosms were randomly assigned to four hydrologic treatments involving two water depths (no standing water and ~10-cm of standing water) and two hydraulic loading rates (10 and 30 cm week−1). Nearby agricultural ditch water was pumped to provide weekly hydraulic loading rates to the mesocosms. During the two-year period, the net mass retention of phosphorus from the water was estimated to have averaged 1.0 g P m−2 in the wetland mesocosms with a higher hydraulic loading rate, while the highest estimated net nitrogen mass retention (average 22 g N m−2) was shown in the wetland mesocosms with 10 cm of standing water and higher hydraulic loading rate. Our finding suggests that hydrologic conditions, especially water level, contribute directly and indirectly to nutrient retention, partially through the quick response of the wetland vegetation community. This study provides valuable information for scaling up to restore significant areas of wetlaculture/wetlands in the former Great Black Swamp, strategically focused on reducing the nutrient loading to western Lake Erie from the Maumee River Basin.

Influence of the Key Process Parameters in Hydrodynamic Deep Drawing Utilizing a Combined Floating and Static Die Cavity

This study focus on the effects of the key process parameters during a modified hydrodynamic deep drawing utilizing a combined floating and static die cavity (HDDC). A two-stage hydraulic loading path is recommended in the novel process, and each stage of the hydraulic loading path is a linear loading path with an inflection point. The method to evaluate the wrinkle and forming dimension precision of the formed parts is introduced at first. Then the influence of the key parameters of the two-stage hydraulic loading path as well as the blank holder force on the dimension accuracy and surface quality of the formed parts was studied in detail. The results showed that the influence of the liquid pressure during the second stage is more significant than that in the first stage in hydrodynamic deep drawing utilizing a combined floating and static die cavity. The initial pressure of the second stage and the maximum pressure arriving moment during this stage have a significant impact on the dimensional accuracy of the formed parts, and the smaller initial pressure or the later the maximum pressure of the second stage arrives, the higher the accuracy of the formed part is. Similarly, the influence of the blank holder force in the second stage on the forming accuracy is more significant than that in the first stage.

PENGARUH HYDRAULIC LOADING RATE (HLR) TERHADAP PENGOLAHAN LEACHATE DENGAN MENGGUNAKAN METODA MULTI SOIL LAYERING (MSL)

Leachate atau lindi sampah berpotensi untuk mencemari air pemukaan dan air tanah. Hal ini diakibatkan degradasi biologis leachate menghasilkan pencemar berbahaya seperti zat organik dan logam berat. Penelitian ini bertujuan untuk mengamati efisiensi MSL dalam mereduksi pencemar yang terkandung dalam leachate. Pengamatan penelitian difokuskan pada pengaruh hydraulic loading rate (HLR) terhadap efisiensi reduksi pencemar, yang terdiri atas 250 l/m2.hari, 500 l/m2.hari dan 1000 l/m2.hari. Penelitian ini dilakukan dengan cara mengalirkan secara gravitasi leachate Tempat Pemprosesan Akhir (TPA) Talang Gulo ke reaktor MSL berdimensi 15x50x50 cm. Reaktor MSL terdiri atas lapisan impermeable dan lapisan permeabel. Lapisan impermeabel merupakan lapisan yang terdiri atas campuran tanah dan arang dengan rasio 2 : 1, serta lapisan permeabel terdiri atas lapisan zeolit berdiameter 0,25 – 0,5 cm. Berdasarkan hasil penelitian, didapat bahwa MSL dapat menetralkan pH dan mereduksi konsentrasi pencemar COD, amoniak, besi (Fe) dan warna. Efisiensi reduksi untuk semua pencemar berkisar 92% – 99,966%. Secara umum, HLR sangat mempengaruhi efisiensi reduksi, dimana makin rendah HLR maka makin rendah konsentrasi outlet serta makin tinggi efisiensi reduksi.

PENGARUH HYDRAULIC LOADING RATE (HLR) TERHADAP PENGOLAHAN LEACHATE DENGAN MENGGUNAKAN METODA MULTI SOIL LAYERING (MSL)

Leachate atau lindi sampah berpotensi untuk mencemari air pemukaan dan air tanah. Hal ini diakibatkan degradasi biologis leachate menghasilkan pencemar berbahaya seperti zat organik dan logam berat. Penelitian ini bertujuan untuk mengamati efisiensi MSL dalam mereduksi pencemar yang terkandung dalam leachate. Pengamatan penelitian difokuskan pada pengaruh hydraulic loading rate (HLR) terhadap efisiensi reduksi pencemar, yang terdiri atas 250 l/m2 .hari, 500 l/m2 .hari dan 1000 l/m2 .hari. Penelitian ini dilakukan dengan cara mengalirkan secara gravitasi leachate Tempat Pemprosesan Akhir (TPA) Talang Gulo ke reaktor MSL berdimensi 15x50x50 cm. Reaktor MSL terdiri atas lapisan impermeable dan lapisan permeabel. Lapisan impermeabel merupakan lapisan yang terdiri atas campuran tanah dan arang dengan rasio 2 : 1, serta lapisan permeabel terdiri atas lapisan zeolit berdiameter 0,25 – 0,5 cm. Berdasarkan hasil penelitian, didapat bahwa MSL dapat menetralkan pH dan mereduksi konsentrasi pencemar COD, amoniak, besi (Fe) dan warna. Efisiensi reduksi untuk semua pencemar berkisar 92% – 99,966%. Secara umum, HLR sangat mempengaruhi efisiensi reduksi, dimana makin rendah HLR maka makin rendah konsentrasi outlet serta makin tinggi efisiensi reduksi.

MODELING THE TORQUE OF THE HYDRAULIC VOLUME DRIVE WITH THE PARAMETERS OF THE HYDRAULIC LOADING DEVICE

Currently, manufacturers for a reliable assessment of the technical condition of volumetric hydraulic drives use the dynamic test method, which allows you to determine the torque (braking) moment on the shaft of the tested hydraulic motor. There are difficulties in reliably determining the value of the developed torque (braking) moment. (Research purpose) The research purpose is in constructing a mathematical model of the relationship between the developed torque (braking) moment of a volumetric hydraulic drive and the parameters of a hydraulic loading device. (Materials and methods) The article presents a hydraulic loading device that provides the necessary braking torque on the shaft of the tested hydraulic motor. Authors conducted one-factor and multi- factor experiments-dynamic tests of the new Sauer-Danfoss series 90 volumetric hydraulic drive using a hydraulic loading device. The torque (braking) was monitored using a non-contact digital torque sensor M 425 3-A datum electronics and a digital indicator with LCD display (Results and discussion) As a result of one-factor passive experiments, the factors influencing the optimization parameter and the ranges of their variation were determined. A mathematical model of the relationship between the developed torque (braking) moment of a volumetric hydraulic drive and the parameters of a hydraulic loading device was obtained by a multi-factor active experiment. The article presents a complete planning matrix for a multi-factor active experiment, which reflects the sequence of all possible combinations of factors that affect the optimization parameter. The most significant factors affecting the value of the developed torque (braking) moment were: the pressure drop and the temperature of the working fluid in the hydraulic lines of the hydraulic loading device. (Conclusions) The mathematical model allows us to determine with high accuracy the developed torque (braking) of the volumetric hydraulic drive.