Soil Treatment Plant Research Articles

On-site wastewater treatment and reuses in Japan

On-site wastewater treatment poses a challenging problem for engineers. It requires a balance of appropriate levels of technology and the operational complexity necessary to obtain high-quality effluent together with adequate reliability and simplicity to accommodate infrequent maintenance and monitoring. This review covers how these issues have been addressed in on-site wastewater treatment in Japan (termed johkasou). On-site systems in Japan range from outmoded designs that discharge grey water directly into the environment to advanced treatment units in high-density areas that produce reclaimed water on-site. Japan is a world leader in membrane technologies that have led to the development of on-site wastewater treatment units capable of water-reclamation quality effluent. Alternative ideas being pursued for on-site technologies also include separate waste stream collection, which would provide for more efficient treatment and reuse. Night soil treatment plants, where sludge from on-site systems is treated, are also distinctive to Japan, serving 37 million people. Japan has governmental regulations in place to ensure routine inspections of on-site units; furthermore, subsidies are available to reduce the cost of on-site systems for building owners. Lessons learned in on-site wastewater treatment in Japan have applications worldwide, from regions where water is scarce, to high-density areas in developing countries that currently lack sewer infrastructures.

Characterisation of acidic sites of Pseudomonas biomass capable of binding protons and cadmium and removal of cadmium via biosorption

The ability of Pseudomonasaeruginosa to accumulate Cd(II) ions from wastewater industries was experimentally investigated and mathematically modelled. From the potentiometric titration and non-ideal competitive analysis (NICA) model, it was found that the biomass contains three acidic sites. The values of proton binding (pKi=1.66±3.26×10−3, 1.92±1.63×10−4 and 2.16±3.79×10−4) and binding constant of cadmium metal ions (pKM1=1.99±2.45×10−3 and pKM2=1.67±4.08×10−3) on the whole surface of biomass showed that protonated functional groups and biosorption of Cd(II) ions could be attributed to a monodentate binding to one acidic site, mainly the carboxylic group. From the isothermal sorption experimental data and Langmuir model, it was also found that the value of Langmuir equilibrium (pKf) constant is 2.04±2.1×10−5 suggesting that the carboxyl group is the main active binding site. In addition, results showed that the maximum cadmium capacity (qmax) and affinity of biomass towards cadmium metal ions (b) at pH 5.1 and 20 min were 96.5±0.06 mg/g and 3.40×10−3± 2.10×10−3, respectively. Finally, interfering metal ions such as Pb(II), Cu(II), Cr(III), Zn(II), Fe(II), Mn(II), Ca(II) and Mg(II) inhibited Cd(II) uptake. Comparing the biosorption of Cd(II) by various Pseudomonas isolates from contaminated environment samples (soil and sewage treatment plant) showed that maximum capacities and equilibrium times were different, indicating that there was a discrepancy in the chemical composition between biomasses of different strains.

2차처리장 방류수 정화 부들습지셀의 초기운영단계 질산성질소 제거

Nitrate removal was examined from May to October 2003 of a surface flow treatment wetland cell, which was a part of a treatment wetland system composed of four wetland cells and a distribution pond The system was established on rice paddy near the Kohung Estuarine Lake located in the southern part of the Korean Peninsula. Effluent from a secondary-level night soil treatment plant was funneled into the system. The investigated cell, 87 m in length and 14 m in width, was created in April 2003. An open water was designed at its center, which was equivalent to 10 percent of its total area. Cattails (Typha angustifolia) were transplanted from natural wetlands into the cell and their stems were cut at about 40cm height from their bottom ends. Average of effluent from the treatment plant was funneled into the cell by gravity flow and average of its treated effluent was discharged into the Sinyang Stream flowing into the lake. Its water depth was maintained about 0.2 m and its hydraulic detention time averaged 5.2 days. Average height of the cattail stems was 42.5 cm in May 2M3 and 117.7 cm in September 2003. The number of stems averaged in May 2003 and in September 2003. The growth of cattails was good. Temperature of influent and effluent averaged 25.9 and , respectively. -N loading rate of influent and effluent averaged 176.67 and , respectively. Removal of rf03-N averaged and its removal rate by mass was about 50%. Considering its initial operating stage in which cattail rhizomes and litter layer on the bottom were not Idly established, the -N removal rate of the cell was rather good.

The fate and behaviour of human estrogens in a night soil treatment process

A night soil treatment plant which collects a high amount of human urine and excreta, is a very unique system to Japan and the object of this investigation on the fate and behavior of the human estrogens in the water treatment process. Water and sludge samples at different treatment phases were taken at a night soil treatment plant. Their hydrophobic fractions were assayed using an in vitro yeast assay (yeast estrogen screen) and an enzyme immunoassay (ELISA) employed for the detection of overall estrogenic activity and 17β-estradiol (E2), respectively. Estrogenic activity observed by the yeast assay was quantified as E2 concentration equivalent, which was comparable with E2 concentration measured by the ELISA, in order to estimate the contribution of E2 to the total activity. Based on the ELISA results, a sketch of the mass balance of E2 in the treatment system was drawn and treatability of E2 was discussed.

An LCA study on sludge retreatment processes in Japan

The majority of night soil (human excrements) is source separated from other sewage water and treated at night soil treatment plants in Japan. Efforts have been made to achieve material recovery from this organic mass, together with other organic wastes such as kitchen wastes and manure, by expanding the functions at night soil treatment plants. These facilities with expanded function are called ‘sludge retreatment centers’, which are promoted by the Japanese Ministry of Health and Welfare. Potential environmental impacts of sludge retreatment using two presently available systems in Japan are analyzed for comparison. Systems compared are: 1) Mebius system, a high-speed fermentation process with methane gas recovery and compost production and 2) a comparable system with a basic composting process. The functional unit for this study is concurrent treatment of 40 t/d of kitchen waste, 40 m3/d of night soil, and 60 m3/d of private sewage treatment tank sludge. Impact assessment on Global Warming (IPCC 1996, 20 yrs.), Acidification Potential (De Leeuv — AP), Eutrophication Potential (De Leeuv- EP) and Resource Index (Fava/SETAC & Heijungs) all indicated that sludge retreatment with Mebius system provides a better environmental performance. The main reasons are: 1) production of power using recovered methane and 2) reduction of sludge volume by digestion, which leads to reduction of fuel required for sludge drying. The collection and treatment of night soil and kitchen wastes involves many economic and social factors. Therefore, more studies with different functional units on these systems should be made to obtain a more complete picture that can be used for decision-making processes. The results of this study can be used as a starting point.

Rare earth elements and other trace elements in wastewater treatment sludges

In order to evaluate the possibility of contamination of soil with trace elements by the application of sludges to soil, the contents of rare earth elements (REEs; La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) and other trace elements (Be, As, Ag, Cd, Sb, Cs, Bi, and U) in wastewater treatment sludges were determined. In sludges of night soil treatment plants (night soil sludges) and sludges of wastewater treatment plants in the food industry (food industry sludges), the distribution patterns of REEs normalized versus average REEs in the continental crust were almost flat. It was considered that the REE patterns of uncontaminated sludges reflected the pattern of the continental crust. The crust-normalized REE patterns of sludges of wastewater treatment plants in the chemical industry (chemical industry sludges) and municipal sewage sludges did not always show flat plots. The sludges that did not show a flat REE pattern were considered to be contaminated with some of the REEs. The coefficient of variation of each element determined among the 10 samples of night soil sludges and the 14 samples of sewage sludges ranged from 34 to 77% and from 26 to 84%, respectively. Among the 10 samples of food industry sludges and the 10 samples of chemical industry sludges, the coefficient ranged from 60 to 143% and from 67 to 172%, respectively. The variations of the content of each element among the food industry sludges or the chemical industry sludges were larger than those among the night soil sludges or the sewage sludges. The contents of Be, As, Cs, REEs, and U in all the sludges were lower than or the same as those in a field soil. Some of the food and chemical industry sludges contained larger amounts of Ag, Cd, and Sb than the soil. All the night soil sludges and sewage sludges contained much larger amounts of Ag and Bi than the soil.

Nitrous oxide emission during nitrification and denitrification in a full-scale night soil treatment plant

Nitrous oxide (N2O) emissions from nitrification-denitrification processes in a full-scale night soil treatment plant were measured, and patterns and control of the N2O production were investigated. Estimated N2O emissions ranged from 4.4 to 1,190 gN/(m3 of influent), corresponding to a conversion ratio of influent nitrogen to N2O-N of 0.24-55%. N2O was produced in the intermittent aeration tank (IAT) where nitrification and denitrification were carried out alternately. The produced N2O was either stripped out to the off-gas or remained in the effluent in dissolved form. The former accounted for more than 99.5% of the total emissions. The latter flowed into the following anoxic tank, where 60-98% of N2O was reduced. A significant difference in the extent of N2O supersaturation in mixed liquor of IAT was observed between the cases of high and low N2O emissions. In IAT, N2O tended to be produced discretely either in aerobic or in anoxic phases. It seemed that the completeness of nitrification and denitrification in IAT, indicated from a mass balance between NH4-N and NO3-N and from NO2-N accumulation in mixed liquor of IAT, was one of the important factors affecting the N2O production. This completeness was decided by the time ratio of aerobic and anoxic phases. External addition of methanol to IAT seemed to reduce N2O emissions.

A proposal of a recycling center for waste soil

Amount of waste soil from construction activities is increasing year by year. Some 437 million cubic meters of the waste soil is generated in a recent year. Much of this soil is disposed to disposal sites, some in-land and some sea bottom, which cannot be considered as an effective usage of the waste soil. In this study.a waste soil recycling promotion center is proposed which enables more effective recycling of the waste soil. A feasibility study is also carried out for a soil treatment plant which is an indispensable part of this waste soil recycling scheme.

Nitrous oxide emission during nitrification and denitrification in a full-scale night soil treatment plant

Nitrous oxide (N2O) emissions from nitrification-denitrification processes in a full-scale night soil treatment plant were measured, and patterns and control of the N2O production were investigated. Estimated N20 emissions ranged from 4.4 to 1,190 gN/(m3 of influent), corresponding to a conversion ratio of influent nitrogen to N2O–N of 0.24–55%. N2O was produced in the intermittent aeration tank (IAT) where nitrification and denitrification were carried out alternately. The produced N2O was either stripped out to the off-gas or remained in the effluent in dissolved form. The former accounted for more than 99.5% of the total emissions. The latter flowed into the following anoxic tank, where 60-98% of N20 was reduced. A significant difference in the extent of N2O supersaturation in mixed liquor of IAT was observed between the cases of high and low N2O emissions. In IAT, N2O tended to be produced discretely either in aerobic or in anoxic phases. It seemed that the completeness of nitrification and denitrification in IAT, indicated from a mass balance between NH4-N and NO3-N and from NO2-N accumulation in mixed liquor of IAT, was one of the important factors affecting the N2O production. This completeness was decided by the time ratio of aerobic and anoxic phases. External addition of methanol to IAT seemed to reduce N2O emissions.

有害物質・障害生物の水環境への影響と制御 都市水環境中に存在するヒト食生活由来の遺伝毒性物質のリスク評価

Genotoxic activities have been detected in the river water. The umu test, which can detect DNA damage, was carried out with blue rayon extracts of various water samples from the river systems and treatment plants. HPLC fractionations followed by MS or UV analysis were applied to the extracts to identify the genotoxic substances. Trp-P-2 (3-amino-1-methyl-5H-pyrido[4,3-b]indole), which is one of mutagenic and carcinogenic heterocyclic amines, was detected in concentration from 1 μg·l-1 to 1 ng·l-1. These results show that carcinogenic substances related to humans' daily diet remain after usual biological treatment. To evaluate the level of Trp-P-2, the added risks were calculated by use of the doseresponse relationships obtained in a carcinogenic animal experiment with mice. The values at assumed exposures of 2l per day of samples from the night soil treatment plant over an average life span of 70 years for 70kg person were in excess of 10-6. Because of the possibility of the reuse of wastewater, the need for the investigation on the safety of the secondary effluent from the treatment plants was suggested.

Case study: Using soil washing/leaching for the removal of heavy metal at the twin cities army ammunition plant

AbstractCOGNIS TERRAMET® soil leaching and Bescorp soil washing systems have been successfully combined to remediate an ammunition test burn area at the Twin Cities Army Ammunition Plant (TCAAP), New Brighton, Minnesota. This cleanup is the first in the country to successfully combine these two technologies, and it offers a permanent solution to heavy metal remediation. Over 20,000 tons of soil were treated in the project. The cleaned soil remained on‐site, and the heavy metal contaminants were removed, recovered, and recycled. Eight heavy metals were removed from the contaminated soil achieving the very stringent cleanup criteria of <175 ppm for residual lead and achieving background concentrations for seven other project metals (antimony, cadmium, chromium, copper, mercury, nickel, and silver). Initial contaminant levels were measured as high as 86,000 ppm lead and 100,000 ppm copper, with average concentrations over 1,600 ppm each. In addition, both live and spent ordnance were removed in the soil treatment plant to meet the cleanup criteria. By combining soil washing and leaching, COGNIS and Bescorp were able to assemble a process which effectively treats all the soil fractions so that all soil material can be returned on‐site, no wastewater is generated, and the heavy metals are recovered and recycled. No hazardous waste requiring landfill disposal was generated during the entire remedial operation.

Evaluation Of Genotoxic Potency On Substances Contained In Night Soil And Its Reduction Performance By Ozonation

Abstract Bacterial assay which can detect the genotoxicity, induction of error-prone repair genes on DNA was applied to samples which were collected at a night soil treatment plant. The genotoxicity of each sample was measured by using this bacterial assay, called the umu test. Strong genotoxic potency was found in the sediments of raw night soil, that is, human feces. There are some substances which show toxicity to the DNA and are attributable to the baked foods or metabolites in human digestive organs. These potencies could not be removed easily in the biological decomposition process through survey of the treatment plant. It was quite clear that more effective reduction could be achieved by ozonation at the treatment condition of about 1 mg O3/mg C.

Denitrification Treatment of NO3-N Polluted Sea Water by Immobilized Acclimated Marine Denitrifying Sludge.

The preparation of acclimated marine denitrifying sludge (AMDS) with high denitirifying activity from activated sludge obtained from night soil treatment plant employing a sea water dilution system was successful within only one month of acclimatizing period. The optimum pH and temperature for denitrification by the AMDS were 6-8 and 30°C, respectively. AMDS was successfully immobilized by PVA-freezing method. Continuos denitrification experiments of NO3-N polluted synthetic sea water using column type bioreactor packed with these immobilized AMDS were carried out. Maximum allowable NO3-N loading rate to obtain 90% of NO3-N removal was determined experimentally to be 6.0 mg-NO3-N/g-pellet/d.

Treatment of exhaust gases from a night soil treatment plant by a combined deodorization system of activated carbon fabric reactor and peat biofilter inoculated with Thiobacillus thioparus DW44

The exhaust gases from a night soil treatment plant were treated by a pilot-scale two-stage deodorization system consisting first of an activated carbon fabric (ACF) reactor and then a peat biofilter inoculated with Thiobacillus thioparus DW44 for a period of about 2.5 months at space velocities (SV) of 300 and 500 h −1. The stable removal ratios for dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in this two-stage system continued longer than in a peat biofilter used shown in a previous study (J. Ferment. Bioeng., 76, 55, 1993), mainly because hydrogen sulfide (H 2S) and methanethiol (MT) were oxidized first in the ACF filter, thus significantly reducing the decline of the pH in the second peat biofilter. The two-stage system was also found to be more easily operated than the single-stage peat biofilter in terms of the water supply requirements and stabilization of the peat to guarantee microbial activity. As the DMS removal ratio was reduced at an SV of 500 h −1 even when the pH was stably maintained, it was assumed that DW44 was metabolically overloaded with respect to its ability to remove DMS at an SV of 500 or more.

Removability of malodorous gases from a night soil treatment plant by a pilot-scale peat biofilter inoculated with thiobacillus thioparus DW44

Thiobacillus thioparus DW44, which degrades hydrogen sulfide (H 2S), methanethiol (MT), dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) was inoculated into a pilot-scale peat biofilter installed in a night soil treatment plant. These gases emitted from the plant were treated at various space velocities(SV) from 46 to 500 h −1. The removal ratios for the gases were more than 95% up to a SV of 300 h −1 if pH was properly controlled. At SV 500 h −1, a rapid decline in pH reduced the removal activity by DW44, mainly due to a decrease in the number of DW44 cells in the peat. The permissible inlet sulfur loads of peat inoculated with DW44 for H 2S, MT, DMS and DMDS were determined to be around 2.0, 0.07, 0.03 and 0.004 g-S-kg-dry peat −1.d −1, respectively.

Nitrification of NH 4-N polluted sea water by immobilized acclimated marine nitrifying sludge (AMNS)

Acclimated marine nitrifying sludge (AMNS) prepared from activated sludge obtained from a night soil treatment plant equipped with a sea water dilution system for controlling the reactor's temperature was successfully immobilized using a polyvinyl alcohol (PVA) freezing method. About 2 weeks of recovery culture was required before continuous treatment could be carried out. Transmittance electron microscopic observations of sliced immobilized AMNS pellets indicated that bacteria with an intracytoplasmic membrane dominated the AMNS colony. Continuous nitrification experiments of NH 4-N containing synthetic sea water were carried out in a 1.2 l bioreactor containing 57.2 g (wet weight) of immobilized AMNS pellets. The NH 4-N removal rate reached a saturation level above an NH 4-N loading rate of 1.5 mg-NH 4-N/g-pellet/d. The maximum allowable NH 4-N loading rate necessary to obtain 90% NH 4-N removal was found to be 1.0 mg-NH 4-N/g-pellet/d. It was possible to store the immobilized AMNS pellets in a refrigerator for at least 1 week without loss of nitrifying capability. Inorganic carbon source was shown to be a limiting factor in the continuous nitrification experiments. The maximum allowable NH 4-N loading rate needed to obtain 90% NH 4-N removal increased to 2.0 mg-NH 4-N/g-pellet/d through supplementation of an inorganic carbon (IC) source to the influent synthetic sea water.

Preparation of marine nitrifying sludge

Activated sludge taken from night soil treatment plants which employ a sea-water dilation system to decrease the temperature elevation caused by fermentative heat during operation was proved to be a good seed source for the preparation of acclimated marine nitrifying sludge (AMNS). The preparation of AMNS with high nitrifying activity was successful from seed activated sludge obtained from a night soil treatment plant which uses a sea-water dilution system throughout the year, within only a two-month acclimatizing period, by applying the fill and draw cultivation method. The nitrifying activity of our newly prepared AMNS was 13.1 mg-NH 4-N/g-MLSS/h, which is comparable to that of fresh water nitrifying sludge. The AMNS was composed of 50 to 100 μm bacterial flocs and showed an excellent settling property. The AMNS exhibited high nitrifying activity, even at a low sodium concentration, but its activity decreased at sodium concentrations above 10g/ l. The optimum pH for nitrification by the AMNS was 8.5 and its nitrifying activity did not greatly change within the pH range of 7.0 to 9.0. The optimum temperature for nitrification by the AMNS was 35°C. The nitrifying reaction of the AMNS was proved to be less sensitive to temperature change.

光硬化性樹脂プレポリマーを用いる脱窒菌の固定化に関する研究

The denitrifiers isolated from the activated sludge of night soil treatment plant were immobilized using a photo-crosslinkable resin prepolymer.Denitrifying activity was strongly inhibited during the first period but the activity was increased in the medium containing nitrate and recovered after 1 day. Acetate was an effective hydrogen source and soap was also effective. Methanol could not serve as a hydrogen source. The optimum pH for denitrification by the immobilized bacteria was 7.0 for nitrite and 7.5 for nitrate, and the optimum temperature ranged 30°C to 40°C. The lowest CH3COONa/NOx-N ratio nessary for getting the highest activity was 4 for nitrite (BOD/NO2-N=2) and 5 for nitrate (BOD/NO3-N=2.5).Photo-crosslinkable resin prepolymer gels exhibited stable denitrification activity to the secondarily treated sewage contained 70mg/l of soap.

特集 し尿処理 膜分離技術の応用

特集 し尿処理 膜分離技術の応用

特集 し尿処理 し尿処理施設とその環境影響

特集 し尿処理 し尿処理施設とその環境影響