Peculiarities of water-soil regime in the process of waste irrigation from livestock complexes

Rational use of natural resources is one of the most acute problems not only in Belarus, but throughout the world. The development of industry, transport and the use of high-intensive technologies in agricultural sector result in the increase of air, land and water pollution. At the same time, wastewater is one of the sources of pollution, despite the fact that much attention is paid to their treatment and neutralization. Currently, various technologies are used for the disposal and treatment of livestock waste. One of them is the utilization of livestock waste for fertilizer irrigation of crops. For practical implementation of fertilizer irrigation, specialized reclamation systems have been built, a technology at the complexes that is based on the principle of full water circulation. Typically, such systems include a network of underground pipelines and irrigation equipment for irrigation, various purpose hydraulic structures, a fence and a drainage network for collecting contaminated surface and drainage water, which accumulate and reuse it for irrigation. When analyzing the operation of such water circulation system, at first glance it seems that the spread of pollution outside the irrigated territory is excluded. However, practical experience shows that complete cleaning and environmental safety, even on advanced systems, is not provided. Therefore, the performance of individual elements of the water reclamation system for fertilizer irrigation requires in-depth study and improvement.

Beneficiation of recycled process water at DRDGOLD's ERGO plant, and its effect on gold recovery

SYNOPSIS To conserve fresh water resources and comply with environmental regulations, DRDGOLD, a South African gold producer re-treating surface tailings, has transitioned to a fully closed water circulation system. Consequently, the accumulation of contaminants, as well as addition of reagents, has led to changes in water composition that have compromised leach performance and overall gold recovery. A two-sample t-test confirmed a significant difference in gold recoveries between the use of Rand Water, which was used as a benchmark, and untreated process water. Atomic absorption analysis of ERGO's process water, confirmed the presence of iron, nickel, zinc, and manganese. A study of the effect of the identified contaminants on gold recovery showed that iron, nickel, and zinc have the largest negative effect on gold recovery, with iron and nickel being more detrimental than zinc. Sulphates were shown to have a possible passivation effect, which also influenced gold recoveries, although to a lesser extent than the heavy metals. Calcium, when present in excess, had a positive influence on gold recovery indicating the possible formation of a calcium aurocyanide complex. Lime softening successfully reduced the heavy metal and sulphate concentrations, and the gold recoveries obtained with the treated process water were similar to those as achieved with Rand Water. Keywords: gold tailings, re-processing, water quality, gold recovery.

Modeling and Analysis of Iron Mass Transfer Behaviors in Supercritical Boiler Steam-Water System

Iron (Fe) concentration is a crucial parameter for boiler safety. However, as the working fluid circulation circuits cross each other, and the working fluid operational parameters change over a wide range, monitoring the Fe content and evaluating pipeline safety are very difficult. The mass transfer process of Fe in a complex water circulation system was described by constructing a network calculation model of Fe mass transfer in the steam-water circulation system of a supercritical boiler. The distribution of Fe and the corrosion/deposition rate in the system was calculated and analyzed. The influence of a Fe mass disturbance in single or multiple equipment on the mass distribution of Fe in the system is discussed. The results show that model calculation data is close to the operational data. Under the effect of cyclic mass transfer, both the granular and dissolved Fe cannot be ignored. During one cycle, about 36% of Fe was deposited on the system tube; however, the deposition amount in the steam generator and superheater section accounted for 81.2% of the total deposition amount, and the rest was deposited in the low-temperature pipeline. The influence of disturbance on other nodes in the network is quite different, which provides the possibility of discriminating the location of the disturbance node. The research results can provide a theoretical reference for water chemical control and safety during the operation.

Microplastic Depuration on Asaphis Detlorata

Depuration is an effort to reduce/eliminate contamination including microplastics, which one is using a water circulation system. This study aims to determine the effective depuration time to reduce the microplastic content in Asaphis detlorata This study used a quantitative approach with experimental research design with a completely randomized design. There are 450 shells used as an experimental animal where is the treatment consisted of four depuration times, namely 1;2;3; and 4 days with 3 repetitions of each treatment, while the control shells were without depuration. Analysis of variance (ANOVA) was used to see the effect of depuration treatment on the microplastic content. If the effect of the treatment was significantly different, then the post hoc test was continued to determine the differences between treatments. The results showed that Asaphis detlorata obtained from the mouth of the Lakatong river estuary were contaminated with microplastics ranging from 0.6 to 8.1 MPs/shellfish and an average of 3.96 MPs/shellfish. Depuration time significantly affected the microplastic content in shellfish depuration effectiveness. There is a tendency that the longer depuration time is decreased microplastic content in shellfish. The effective depuration time to reduce the microplastic content in Asaphis detlorata was 3 and 4 days. Further research is needed for a more effective depuration for cleaning microplastics in shellfish.

A Novel Ultrasonic Cleaning Tank Developed by Harmonic Response Analysis and Computational Fluid Dynamics

The manufacturer of an ultrasonic cleaning tank (UCT) received advise from a customer to seek the cause to why the UCT could not clean their products effectively and develop a novel UCT to replace the conventional model. This UCT had a capacity of 10 L, a frequency of 28 kHz, four horn transducers, and a total power of 200 W. To resolve that problem and respond to customers’ needs, we presented new methods to develop the UCT using the harmonic response analysis (HRA) and computational fluid dynamics (CFD) to simulate the cleaning process which occurred within the UCT based on the actual conditions. Results from the HRA showed that the acoustic pressure in a problematic UCT was low, resulting in a smaller cleaning area, which was consistent with the results from the foil corrosion test, and thus caused the cleaning process to be ineffective. We developed a novel UCT with improved effectiveness by adjusting the design and adding a water circulation system. From the HRA, we were able to design the dimensions of the UTC and position of the transducer to be suitable to increase the acoustic pressure and cleaning area. CFD results enabled us to design proper inlet and outlet shapes, as well as simulate the water flow behavior to find the optimal cleaning condition so the novel UCT had a water circulation system that could eliminate the excess particles.

A unit-cell model for thermal regulation of degradation of organics in solid waste

It is a well appreciated fact that temperature is one of the key factors influencing the degradation of organics. Heat exchangers are a viable option that can be used to adjust the temperature in solid waste to an extent most suitable for waste degradation. This paper focuses on an experimental and theoretical investigation of the feasibility of using a water-circulating heat exchanger for thermal regulation of waste degradation. A cylindrical bioreactor with a central pipe connected to a water circulation system is devised and instrumented. The changes in temperature and gas production were monitored during the degradation of the organic component of the waste. Test results with and without thermal regulation are analyzed and compared. In addition, an analytical model is proposed to simulate the symmetrical heat transport behavior subjected to heat exchange. Heat generation due to the degradation of organics is taken into account. There was a good correlation between the analytical model prediction and the experimental data obtained from the laboratory test and field monitoring.

Mapping of Domestic Hot Water Circulation Losses in Buildings – Preliminary Results from 134 Measurements

The hot water circulation system in a building is a system which helps prevent Legionella problems whilst ensuring that tenants have access to hot water quickly. Poorly designed or implemented systems not only increase the risk to people’s health and thermal comfort, but even result in an increase in the energy needed for this system to function properly. Results from previous studies showed that the total hot water circulation system loss can be as high as 25 kWh/m2 heated floor area per year. The purpose of this project is to measure the total energy use per year of the hot water circulation system in about 200 multifamily dwellings of different ages to verify that a system loss of 4 kWh/m2, year is a realistic assumption for both newer and older/retrofitted buildings. The preliminary results from the first 134 measurements showed that the assumption of 4 kWh/m2, year is rarely fulfilled. An average energy use of more than three times this is more common, even in newer buildings. Whilst some of the total energy lost is used to heat the buildings, it is not desirable because it is an uncontrolled energy flow.