Soil Treatment System Research Articles

Designing slanted soil system for greywater treatment for irrigation purposes in rural area of arid regions

To solve the unpleasant disposal of greywater in rural area and allow its collection for reuse in gardening, a slanted soil treatment system (SSTS) was designed and installed in two households. Granitic gravel of 1–9 mm size was used as the filter medium. The aim of this study was to design a SSTS and assess its suitability as a treatment system allowing greywater reuse in gardening. The efficiency of the SSTS was assessed based on organic matter and bacterial pollution removal. The developed SSTS allowed the collection of greywater from three main sources (shower, dishwashing and laundry) in rural area. The SSTS is efficient in removing at least 50% of suspended solids, chemical oxygen demand and biological oxygen demand. The study highlighted that, contrary to the common perception, greywater streams in rural area are heavily polluted with faecal indicators. The removal efficiency of faecal indicators was lower than 2 log units, and the bacteriological quality of the effluents is generally higher than the WHO reuse guidelines for restricted irrigation. Longer retention time is required to increase the efficiency. The possibility of reusing the treated greywater as irrigation water is discussed on the basis of various qualitative parameters. The SSTS is a promising greywater treatment system for small communities in the rural area in the Sahelian region. To increase the treatment efficiency, future research will focus on the characteristics of the SSTS, the grain size and the establishment of a pretreatment step.

Greywater Characteristics In Rural Areas of the Sahelian Region for Reuse Purposes: The Case of Burkina Faso

The characteristics of greywater generated in two rural areas (“Barkoundba” and “Kologoudiessé”) located in the Sahelian region in Burkina Faso were assessed through observations in selected concessions, sample collection and laboratory analyses. The study aimed at characterizing the qualitative and quantitative characteristics of greywater in order to evaluate its reuse potential for gardening in rural areas. The results showed that greywater is generated from 3 to 4 main sources with average daily productions of 8 ± 1 L•capita‑1•d‑1 in “Barkoundba” and 13 ± 3 L•capita‑1•d‑1 in Kologoudiessé”. Despite these low rates, the average quantity of greywater production varied from 67 to 344 L•concession‑1•d‑1 during the dry season. This greywater can be collected to provide additional water for irrigation in home gardens of size varying from 10 to 43 m2. Shower activity is the major contributor of greywater with up to 56% in “Barkoundba” and 70% in “Kologoudiessé”. The qualitative assessment of the greywater streams showed that every source is contaminated with chemicals and microbial pollutants at levels not suitable for direct reuse in agriculture. Therefore, it is recommended to treat the greywater before its use for irrigation purposes. Based on World Health Organization (WHO) reuse guidelines, the treatment system should be able to remove bacteria by more than 2 log units and 4 log units if restricted and unrestricted irrigation are considered respectively. Since shower greywater is directly poured onto the ground, the treatment unit should be adapted to the shower room to allow shower greywater collection, in order to collect the required quantities for gardening. A slanted soil treatment system could be investigated. Hazards of a direct reuse are discussed for soils, plants and human health on the basis of the various qualitative parameters. However, an accurate risk assessment would require further investigations with the evaluation of the interannual variability of greywater quality.

Environmental Impact of Waste Slurry in Pile Foundation Construction of High-Speed Railway Bridges and its Countermeasures

Slurry is a necessary material in high-speed railway pile foundation construction. A lot of waste slurry which is harmful to the eco-environment will be generated after the construction is finished. If the slurry isn’t disposed properly, it will cause serious pollutions to the environment. This paper analyses environmental impact of waste slurry through four aspects: surface water, crops, soil and wastewater treatment system etc. Finally, it gets the conclusion that there are four methods to reduce the environmental pollutions of waste slurry: the first one is using the environment-friendly slurry in pile foundation construction; the second one is raising the slurry use efficiency; the third one is decreasing the amount of slurry usage and the output of waste slurry; the last one is developing the more eco-friendly waste slurry treatment methods.

A SAND LAYER DETERS BURROWING BY LUMBRICUS TERRESTRIS L.

Burrows of anecic earthworms that penetrate the infiltrative surface of soil-wastewater treatment system trenches may contribute to preferential flow through soil macropores in septic system filter fields. Adding a layer of sand on the bottom of the trench, however, may discourage earthworm burrowing. In this laboratory study, we investigated if the particle-size distribution and position of a sand layer would inhibit burrowing by the anecic earthworm Lumbricus terrestris L. Three earthworms were added to the top of soil columns containing a 3-cm-thick sand layer covered with 2 mm of loamy B-horizon material and underlain by 9 cm of the same material. We repeated this experiment with earthworms placed below the sand layer. In another experiment, the sand layer was covered by 11.3 cm of soil material to investigate whether worms added to the surface would avoid crossing a sand layer embedded within the columns. No treatments in the surface sand layer experiments prevented all worms from establishing burrows. The worms added to the surface, however, took an average of 1.7 to 5 times longer (P ≤ 0.05) to establish burrows, and earthworm mortality was greater in columns with a surface sand layer compared with the no-sand-layer controls. In the embedded-sand-layer experiment, no worms burrowed past the soil-sand interface, whereas all worms in the controls burrowed past the equivalent depth. Sand particle size distribution did not significantly affect earthworm burrowing. The results suggest that adding a layer of sand to the bottom of soil treatment system trenches may deter earthworms, but will not restrict burrowing.

Treatment of lower load graywater by using a controlled soil natural treatment system

Experiences of treating graywater by soil natural treatment systems have not been widely reported. In general terms, graywater has a lower concentrations of organic matter; nutrients (e.g. nitrogen), and microorganisms than combined wastewater; therefore, the graywater treatment capacity of soil should be evaluated. In this study, the performance of a natural soil treatment system was evaluated when shower graywater from a house located at Sapporo City, Japan, was treated by a layer of 30 cm of soil from the Hokkaido University Campus. Results showed very high removal efficiencies of chemical oxygen demand (98%) and Kjeldahl nitrogen (95%) at high infiltration rates (214 cm/d), which denotes that natural soil treatment systems could be a good alternative to treat lower load graywater.

Soil-Based Treatment of Partially Treated Liquid Swine Manure

A soil-column system was tested for the removal of soluble organics and nutrients from partially treated liquid swine manure. The liquid manure was applied to the 900 mm deep (300 mm of local topsoil and 600 mm of local subsoil) soil columns continuously for an eight-week period, and leachate as well as soil samples were analysed. An effective liquid manure application rate of 17 mm d−1 was determined based on a preliminary liquid manure soil-based treatment experiment. It was found that more than 90% of five-day biochemical oxygen demand, chemical oxygen demand, total Kjeldahl and ammonia nitrogen, and total phosphorus could be effectively removed from the liquid manure by the soil system. Nitrogen contents accumulated in the soil matrix mostly within the 0 to 300 mm depth, while no significant increase was observed in sub soils. Soil analyses indicated the occurrence of nitrification and denitrification in the soil columns. Nitrogen balance showed that about 42% of the applied nitrogen was lost from the system during the liquid manure soil-based treatment experiment, suggesting the emission of ammonia and other gaseous nitrogen generated through nitrification and denitrification. The leachate of the soil treatment system was used to irrigate Bermuda grass. No negative effect of leachate was observed on the plant growth.

Archaeal diversity in naturally occurring and impacted environments from a tropical region

To evaluate archaeal diversity in natural and impacted habitats from Rio de Janeiro state, Brazil, a tropical region of South America. 16S rRNA gene was amplified directly by polymerase chain reaction (PCR) from genomic DNA, extracted from Guanabara Bay (GB) water, halomarine sediment (HS), municipal landfill leachate, agricultural soil and wastewater treatment (WT) system. Five archaeal 16S rDNA clone libraries were constructed. A total of 123 clones, within the five libraries analysed, were clustered into 29 operational taxonomic units, related to cultivated (24%) and uncultivated (76%) organisms. Rarefaction analysis showed that the libraries contained different levels of diversity. PCR-denaturing gradient gel electrophoresis (DGGE) of 16S-23S intergenic spacer regions confirmed the presence of a dominant phylotype, revealed by the WT system clone library. Archaeal communities of impacted environments seem to be confined to specific ecosystems with similar physicochemical properties, while communities from natural environments appear to be widely distributed. The presence of a high number of phylotypes related to uncultivated organisms suggests new archaeal lineages. This study reports, for the first time, the analysis of archaeal diversity in tropical environments from Brazil, and adds sequences from this region to the developing database of 16S rRNA clone libraries from environmental samples.

Numerical modeling of wastewater transport and degradation in soil aquifer

Modeling of wastewater transport and degradation in soil aquifer is a problem of concern with regard to the optimization of design and operation of the wastewater soil treatment system. To solve this problem, three-dimensional groundwater flow and wastewater transport and degradation model was developed using MODFLOW and MT3DMS modeling. The developed model was calibrated using the Soil Infiltration Treatment System (SITS) in the Chongming island of China after considering the river—groundwater interaction and the regional geological and hydrological conditions. Using the calibrated model, the following problems with regard to the design and operation of SITS were discussed: (1) Allowable hydraulic load. The hydraulic load increases with the drop in the water level of the adjoining river, the increase in the actual soil area under operation, and the increase in the distance among the individual operation units of SITS. (2) Optimized layout of the groundwater monitoring wells. The concentration contour of the simulated contaminants is very useful to depict the typical areas that are most severely polluted and very sensitive to the peripheral environment, thus lesser number of monitoring wells can be set up based on the model, and the goal of the accurate assessment of the influence of soil-infiltrated wastewater on groundwater can be achieved.

On site experiments of the slanted soil treatment systems for domestic gray water

In order to make a breakthrough for the acute problem of water shortage in the world, the key words "decentralization and re-use" are very important for new sustainable sanitation systems that will be developed. Therefore, we focused on a new treatments system called "a slanted soil treatment system" which combines a biotoilet system with a domestic grey water treatment system. Because this system is a low cost and compact system, the system can be easily introduced to homes in urban areas or in the suburbs of cities in many developing countries. In this study, we performed on site experiments carried out on Shikoku Island, Japan, for several years. We obtained the following results. The slanted soil treatment system could remove organic pollutants and total nitrogen and total phosphorus in grey water effectively. Furthermore, the system performance became high in the case of the high concentration of the influent water. The nitrification reaction and denitrification reaction were speculated to exist due to aerobic zones and anaerobic zones present in the slanted soil treatment system. The slanted soil treatment system could perform for approximately 3 years with zero maintenance. The plug flow model of 1st order reaction kinetics could describe the reaction in the slanted soil treatment system. However, it is necessary to improve the system to maintain the performance in all seasons.

Aerobic nitrification–denitrification by heterotrophic Bacillus strains

Twenty-four Bacillus strains predominantly outgrown in a night soil treatment system were isolated and characterized. Under various culture conditions, cell interactions took place among them and cell population changed. Maximum removal of NH 4 + - N and cell production by the isolates occurred under the conditions of 30% DO and C/N ratio of 8. Five dominant isolates were identified to be species of Bacillus cereus, Bacillus subtilis and Bacillus licheniformis with similarities of 78–94%. Additions of 0.8% peptone and 0.3% yeast extract to a basal medium influenced the growth of isolates and the removal of NH 4 + - N in flask culture. Metal ions such as Ca 2+, Fe 2+ and Mg 2+ had a similar effect. The specific growth rates of the five isolates were found to be in a range of 0.43–0.55 h −1. During the flask experiment of nitrogen removal under aerobic growth conditions, active nitrification by the isolates occurred largely in 1 h with a decrease of COD and alkalinity reduced to only 74.6% of theoretical value. From the nitrogen balance, the percentage of nitrogen lost in the flask culture was estimated to be 33.0%, which was presumed to convert to N 2 gas. This conversion of ammonia to N 2 without formation of nitrous oxide under aerobic growth conditions was confirmed by GC analysis. From all the results, it has been found that the Bacillus strains were able to occur simultaneously aerobic nitrification/denitrification and the B3 process using the Bacillus strains seemed to possess some economic advantages.

Toxicological evaluation of hydrocarbon removal from soils by an extraction and solubilization remediation process

Toxicity analyses were performed on manufactured frac sands and construction fill material to assess the efficacy of a pilot scale treatment system designed to remediate environments impacted with organic contaminants. Oiled proppants and backfill were collected from the North Slope in Alaska while unadulterated fill material from the Idaho National Engineering Laboratory (INEL) was collected and then contaminated with crude oil. Two commercial bioassays (Microtox, Polytox) were used to provide toxicological data for process waters, and treated and untreated solids from the soils treatment system. Total extractable hydrocarbon analyses were performed on treated and untreated solids, and indicated removal efficiencies greater than 95% for all samples tested. Microtox testing using sonicated extracts from solids and whole water samples provided the most sensitive and useful toxicological data, showing the soil treatment system to significantly reduce the toxicity of treated solids.

Night soil treatment system equipped with ultrafiltration

The recent history of night soil (human waste) treatment technology in Japan is reviewed together with current trends in membrane filtration treatment. Operation of a high load denitrification human waste treatment facility using membrane filtration is described in detail. Membrane separation devices are shown to operate consistently and smoothly at the designed flux levels for more than 3 y. Good quality treated water can be obtained when special care is given to the biological reaction tank to prevent build-up of high molecular materials that degrade membrane performance.

Night soil treatment system equipped with ultrafiltration

The recent history of night soil (human waste) treatment technology in Japan is reviewed together with current trends in membrane filtration treatment. Operation of a high load denitrification human waste treatment facility using membrane filtration is described in detail. Membrane separation devices are shown to operate consistently and smoothly at the designed flux levels for more than 3 y. Good quality treated water can be obtained when special care is given to the biological reaction tank to prevent build-up of high molecular materials that degrade membrane performance.

Hydrology of Spray-Runoff Wastewater Treatment

Liquid measuring procedures used in a 12-month study of the hydrology of the soil treatment system at Campbell Soup Company's Paris, Texas plant accounted for 93% of the total liquid applied to the soil. The rainfall and wastewater applied to the soil system are accounted for as follows: 18% is lost to the atmosphere through evaporative processes; 61% is recovered as runoff; and 21% percolates through the soil. The fraction of the treated wastewater recovered as runoff ranges from a low of 30% to a high of 85%. This range in the percent runoff is influenced by climate, soil textural class, and wastewater spray schedules. Wastewater spray schedules are controlled to partially offset variations in the percent runoff which would normally occur as the result of climatic influences.