Iranian Journal of

---

Background and Objectives: Heavy metals processing industry has always been a major cause of concern which affects soils, surface waters, ground waters and river sediments contaminations. Thus, the Zanjan Zinc and Lead Smelting Plant has been considered as a potential source of contamination.
Mterials and Methods: This cross-sectional study has been conducted in February 2008 in the site region .The concentrations of Lead, Zinc and Cadmium have been assessed. The samples have been taken from 17 wells and atomic absorption spectrophotometeric method has been used to assess the samples. In order to find out and locate the exact situation of the wells under study, Global Positioning System instrument has been used. The correlation between the concentration of each metal and the distance of studied well from the plant has been assessed too.
Results: The findings of this study showed that lead and cadmium concentrations were 53% and 59% respectively out of the guideline values of World Health Organization.
Conclusion: The concentration of Zinc was lower than both national and international values in all samples. As the heavy metal concentration is very important for human health status, the other fields of study like heavy metal air pollution effects and related diseases and conditions should be studied and assessed.

---

Background and Objectives: Silica is an inorganic material that found in the nature in various forms. The hazards of crystal of silica or α-quartz (free silica) is greater than other forms. Exposure to dust that contains free silica result to pulmonary injury and result to silicosis and death finally. The present research was conducted in order to evaluate the level of workers exposure to free silica in air of Khaf Iron stone quarries.Materials and methods: The exposure level to total and respiratory dust measured based on personal and environmental sampling methods and concentration of dust determined based on gravimetric method. For determination of amounts of free silica, dust samples analyses based on X-ray diffraction (XRD) method, and results compared with standard levels.Results: The maximum amount of total dust and free silica measured in stone breaking station (800±155mg/m³ and 26.11±6.7 mg/m³) and minimum of them measured in official and safeguarding station (8.28±2.2 mg/m³ and 0.012±0.0019 mg/m³). The maximum amount of respiratory dust and free silica measured in red mound digging number 1 (66.14±13.45 mg/m³ and 1.48±0.39 mg/m³) and minimum of them measured in air hammer machine station (5.26±2.62 mg/m³ and 0.01±0.005 mg/m³).Conclusion: Amount of total dust only in official and safeguarding station was lower than standard levels of Iran. Amount of respiratory dust in all stations was greater than Iran standard levels. Furthermore the level of respiratory free silica only in airy hammer machine station was lower than standard level of Iran. Regarding to this amounts it is so essential to that with applying different methods generation and emission of dust protected.

 

---

Background and Objectives:Groundwater treatment by nano particles has received increasing interest in recent years. Chromium is a commonly identified contaminant in soils and groundwater. Zero-valent iron, as a natural reduction agent can be used in controlling of contaminated sites. The aim of this research is investigation of hexavalent chromium removal from aqueous solutions by using of iron nano particles the effective parameters. Materials and Methods: In this research the synthesized of the iron nano particles has performed by addition of NaBH4 to FeCl3·6H2O solution and Cr(VI) reduction efficiency in Batch system was studied. Also the impact of the important field parameters including pH, initial chromium concentration, nano zero valent iron concentration and retention time were investigated.
Results:The results of this research showed that synthesized particles were in nano scale. In pH=3, chromium inlet concentration of 10 mg L-1, nano zero valent iron concentration 0.5 g L-1 and 2 minute retention time, 100% of Cr(VI) was removed.
Conclusion:The concentration of nano zero valent iron had significant effect on the reduction of Cr(VI).The reaction occurred in a wide range of pH value and the reaction efficiency increased significantly with decreasing initial pH. The significant removal efficiency, high rate of process and short reaction time were showed that iron nano particles have significant potential in removal ofCr(VI) from contaminated water.

---

Backgrounds and Objectives:Today the crisis rising from over consumption energy and materialand environmental pollution pose serious problems that challenges present resources of man.Sustainable development is probably an inevitable strategy for human being in such a way that theleast possible damage be inflicted to the environment.In this way, the role played by universities in reaching the objectives of sustainable development is crucial. In this paper, we examine the present state of consumption energy resources (Electricity and natural gas) in the central main campus of Tehran University and so we calculate the extent of environmental pollutants resulted of these energy consumptions.
Materials and Methods: For surveying of our objectives the first step is a survey of the current state of campus by way of reexamination of Gas and Electricity bills and distribution of a questionnaire. Second is an estimate of the entering pollutants to the environment with online software in site of http://www.abraxasenergy.com/emissions.
Results:annual consumption of 16.5 million KWHS of electricity along with 4312392 m3 of naturalgas leads to 0.0218 million tones Co2, 778 kg VOCS, 374.6 tones NOX, 2.41 tones CO, 65.341 tones So2, 93 kg Mercury compounds and 868 kg particles.
Conclusion: It is shown that there is no objective effort and green management in this part ofuniversity officials. This project suggests that the implementation of green management in the framework of programs such as green university can be crucial in reaching the objectives.

---

Backgrounds and Objectives: The school is the most appropriate place for flourishes children, adolescents and juniors, and prepares safe and vigorous life. Thus, the aim of this research is to study  of the hygienic conditions in primary schools in region 1 of Sari city.
Materials and Methods: This article is a descriptive study. In which 45 non-for-profit and governmental schools were sampled using census method. The Fools of sampling was questionnaire filled in during interview with school principals and direct observation. Collected information was analyzed using "Excell" and spss soft wares.
Results: The results of this search showed that %93.4 of schools had dimention smaller than minimum standard. Only in %35.6 of schools, lavatory and drinking places were separate and the quality and quantity of lighting in %32 of. schools were classes proper.
Conclusion: The most important finding of this search was the ignorant of indicators in environmental healthas overlooking of standards, and the schools are merely established on quantity and urgent need despit of their quality.

---

Backgrounds and Objectives: Nitrate is a water contaminant that can cause health problems in human and animals, in addition to eutrophication of the water body. So, Nitrate-contaminated water may be treated by treatment systems. In this study, hydrogenotrophic denitrification using hydrogen produced by Fe0 as an electron donor to nitrate removal was evaluated to assess the feasibility of employing Fe0 in the biological nitrate treatment.
Materials andMethods : Batch experiments were conducted using 250 ml amber bottles at 20-35oC under anoxic conditions. The nitrate concentration in each reactor was 20 mg N/L and triplicate samples were prepared for the following treatment: Fe0 plus cells, Fe0 only, and control. The effect of Fe+2 and temperature on nitrate reduction was evaluated.
Results : 97 percent of Nitrate was reduced within 2 day in a Fe0-cell reactor, while only 30% of the nitrate was abiotically reduced over 2 day at 30 oC. Fe+2, which is produced during anaerobic iron corrosion in the Fe0-cell system, might act as an electron donor for nitrate. Abiotic reduction and microbial reduction of nitrate was significantly affected by temperature conditions. The reduction rate decreased as the temperature deceased.
Conclusion:This study demonstrated the potential applicability of employing Fe0 as a source of electrons for biological nitrate reduction. Use of Fe0 for microbial nitrate reduction can obviate the disadvantages associated with traditional biological denitrification that relies on the use of organic substrates or explosive hydrogen gas.

---

BackgroundsandObjectives: Environmental activitiesunknownprice and value caused establishing of some unique characteristics for mentioned commodities. One of these characteristics was existing gap between private and social cost and benefit. For assessing these activities different approaches include travel cost, willingness to pay and hedonic price had been suggested. According to Tehran's air pollution problem, in this study Hedonic approach had was used for the assessment of healthy air on Tehran's residential house price.
Materials and Method : Hedonic approach is one of the methods that are used for evolution environmental goods. In this method, each good's price is estimated as a functions of that good`s properties. To gather this study information 300 questionnaires has been collected by random sampling from different area of Tehran.
Result: Results revealed that activities in order to reduce air pollutions, in addition to environmental value have economical value form the point of view of consumers. Also, results show that willingness to pay of every Tehran's citizens for every square meter of house located in region with less pollution is between 1120 to 1350 thousands Rials.
Conclusion: According to the obtained results can be said that, clean air as an environmental good from the viewpoint of consumers has economic value that can be calculated this value using methods such as Hedonic.

---

Background and Objectives: This study presents an evaluation between IAQX 1.0f and Fluent 6.3.26 in modeling of NOx dispersion in an indoor residential environment. Modeling predictions are compared with sampling results.
Materials and Methods: Aresidential building with about 84 m2 area is modeled. In IAQX 1.0f the building is divided into five zones. Emission factors and absorption rate of sinks is estimated with US.EPA suggested factors. On the other hand, In the Fluent 6.3.26 model, the building was divided into 1777 cells, and the openings are defined by the boundary conditions of the inflow. In this model, pollution sources were simulated by boundary conditions of the mass inflow.
Results:Compared to IAQX 1.0f, Fluent 6.3.26 showed higher estimation of the concentrations in the zones of 1, 2 and 3. In comparison with the measurements, both models had underestimated results.
Conclusion: The results of Fluent 6.3.26 were closer to the sampling results in the zones.

 

 

---

Background and Objectives: Particular importance of hazardous wastes is due to having characteristics such as toxicity, flammability, corrosively and reactivity. Some of the chemical wastes due to having hazardous materials must be collected and managed in a proper manner, since they are potentially harmful to the environment. Owing to the fact that educational centers have important roles in developing countries, so the main objective of the present study was to investigate, hazardous waste management in chemistry laboratories of Ministry of Science universities, in Tehran, Iran.   
Materials and Methods: Study area of this research includes all chemistry laboratories in Tehran universities which were covered by Ministry of Science. To obtain the number of samples, based on Scientific Principles and identification formula, 64 samples were calculated. In addition, sampling was done by Stratified sampling. Validated checklists were used for data gathering. Data analysis were done by Descriptive statistics (mean, frequency and etc.) and inferential statistics (kruskal- wallis test).
Results: results obtained in this study indicate that Sharif University by obtaining the mean score of 60.5 and Tehran University by obtaining the mean score of 4.5-6 are placed in best and worst rank, respectively. Beheshty, Alzahra and Tarbiat Moallem univesities by acquiring the mean score of 20-28.5 have a same position in ranking table. 
Conclusion: Results show that most of the studied laboratories do not have any collection program and only 26.5 percent of them have acceptable programs.The separation and storing program observed in about 12.5 percent . Hazardous wastes' management in chemistry laboratory of Tehran Universities was not in good status. And from the standpoint of management, only 12.5 percent of studied cases are in good status, while 75 percent was in undesirable status.

---

Background and Objectives: New studies indicate that nitrate concentration in groundwater is increasing in most cities. High concentrations of nitrate in water increase the potential health risk in the community and the environment. In infants, No₃ _ is reduced to No₂ _, which combines with hemoglobin in the blood to form met hemoglobin leading to blue-tinged blood for babies under six months old in particular ,Namely, so-called ‘‘blue baby syndrome&apos&apos and  it  also produce carcinogenic compounds . Therefore high nitrate concentration is important. The aim of the present study is removing nitrate from water using zero_valent iron.
Materials and Methods: Analyses were conducted on synthetic samples. These samples were analyzed considering reaction times, pH, initial nitrate and sulfate concentration.
Results: Results showed that at Nitrate with an initial concentration of 200mg L1^-  after 60 min of reaction at pH(s) 7, 6 and 5 about 67.8%, 72.5 % and 88% was reduced, respectively in concentration of 100 and 300 mgL^- (pH=6) the removal efficiency is 60 and 83 percent, respectively. In sodium sulfate and nitrate with concentration of 300, the removal efficiency reached from 72 to 70 percent.
Conclusion: Results show that the initial pH is important to achieve maximum efficiency of nitrate removal. So the lower pH levels increases removal efficiency of nitrate. All of the experiments indicated that removal is the highest in the first 5 min. Generally with an increasing initial nitrate concentration the removal efficiency of nitrate increases.

---

Background and Objectives: Industrial wastewater included the cyanide is one of the important sources of environmental pollution which founded in Industrial wastewater which are harmful for human health and environment. Therefore, the purpose of this research that was fundamental designed is investigation of Removal of cyanide from aquatic solution by using of iron and copper powder in experimental scale.
Material and Methods: At first, pilot was designed. Then, acquired pH optimum equal to 2,7 for copper and iron by variation pH= (2,4,6,8,12) and constant other parameters. The effect of initial cyanide concentration (40,60,80 mg/l), initial iron and copper dosage (0.08-1 g/100CC) and contact time (15-12 min) studied at the constant of optimum pH. 
Results: The result showed removal efficiency Increased from 46.6% to 90.56% and 31% to 93.78% for copper and iron by increasing of contact time from 15to 120 minute in constant conditions, respectively. Also result showed Removal efficiency decreased and increased by increasing initial cyanide concentration and initial iron and copper dosage. The results showed equilibrium data were explained acceptably by Langmuir isotherms and kinetic parameters were obtained by application of Langmuir&Hinshelwood equation.
Conclusion: The results showed that removal of cyanide can be quick and effective done by iron and copper in experimental scale.

---

MicrosoftInternetExplorer4 Background and Objectives: 2, 4-dichlorophenoxy acetic acid is a well-known herbicide which can be dangerous for  both human and animal health in different ways such as its presence in drinking water. This study aimed at Performance of granular activated carbon to 2-4-D removal from aqueous solution and assessing the relationship between COD and 2-4-D concentration
Materials and Methods: This study is a lab-scale study. Firstly, different 2-4-D concentrations were prepared from Stock solution (1000 mg/L), and then their CODs were measured. Optimum pH for 2-4-D removal was determined and its absorption rate at different concentrations was measured.
Results: Results showed a clear relationship between COD and 2-4-D concentration. On the other hand, COD removal increased as time elapsed, so that maximum removal 90% and 84% at initial 2-4-D concentrations of 50 and 100 mg/L were observed at contact time of 50 min respectively. Optimum pH for all concentrations was determined as 6.
Conclusion: According to present study it can be concluded that activated carbon have be up to 90% of 2-4-D removal from water environment. In addition, a significant relationship was observed between COD and 2-4-D concentration, so that direct measurement of COD can be used instead of 2-4-D measurement.

---

MicrosoftInternetExplorer4 Background and Objectives: Irrigation of agricultural crops using wastewater will increase, in some cases, their growth by 40 to 60 percent. However, this has a high risks for human health because of the presence of higher number of pathogenic organisms. The main purpose of this study was to investigate the feasibility use of Fenton and modified Fenton with copper for the disinfection of raw wastewater.
Materials and Methods: After primarily laboratory physicochemical and biological analysis, the disinfection process was performed in three different phases in each process. First, the disinfectants were injected separately, then we performed disinfection using Fe++ and cu++ ions combined with hydrogen peroxide in order to determine synergistic effect of each catalyst. Direct method was used for fecal coliforms counting. 
Results: Hydrogen peroxide maximum efficiency for inactivation of fecal coliforms was only 0.66log inactivation. Fenton and modified Fenton with copper ions showed a remarkable effect on the bacterial inactivation so that Fenton and modified Fenton with 1 and 2 mg/l of Cu++ inactivated coliforms by 4.73, 3.28, and 4.88 log respectively.
Conclusion: Application of HP alone for the disinfection of raw wastewater is not practicable due to low observed efficiency. However, its combination with ions such as Fe++ and Cu++ increases HP performance in disinfection and has a notable synergistic effect on HP  disinfection power, where, in the presence of each catalyst, hydrogen peroxide can reduce the fecal coliforms of raw wastewater to meet the Iranian Environmental Protection Agency Standards.

---

MicrosoftInternetExplorer4 Background and Objectives: Wind-induced particulate air pollution from iron ore piles can causes environmental and economic problems for steel industries. In this experimental study, the effectiveness of various additives in reducing particulate air pollution from iron ore piles was investigated in a laboratory wind tunnel.
Materials and Methods:  The experimental set up consisted of a prismatic pile and a wind tunnel. Four different wind speeds of 4.3, 5, 7 and 11 m/s was used in the study  Municipal water, quick lime (2%), seawater, treated industrial wastewater and Polylatice (0.25%) were used as additives to stabilize the upper layer of the pile.
Results: Emission factors for non-stabilized (without additive) piles at 4.3, 5, 7 and 11 m /s wind speeds were 46.7, 73.2, 1025.4 and 13768.7 g/m², respectively. Stabilized piles with 2.6, 2.7, 2.8, 2.7 and 2.8 percent additive (moisture content of the upper layer of the pile) for municipal water, Polylattice (0.25%), treated industrial wastewater, seawater and quick lime (2%) indicated a decrease of 99.4%, 100%, 99.3%, 99.5% and 99.5% particulate emission reduction, respectively.
Conclusions: Proper selection and use of additives on iron piles has the potential for decreasing  more than 99% of the wind-induced particulate emissions. Operational factors such as covered area, spray frequency, pile geometry, seasonal adjustments related to ambient temperature and humidity, wind speed and operator training need to be an integral part of the pollutant reduction program.              

---

MicrosoftInternetExplorer4 Background and Objectives: Intake of high concentrations of fluoride in drinking water can cause dental fluorosis. In this study, the prevalence of dental fluorosis in rural communities of East Azerbaijan Province was studied.
Materials and Methods: 3 villages of Bashsizkooh, Bostanabad (fluoride concentration in drinking water = 0.12 mg/L), Nagharehkub,  Ahar (current water resource = 0.6 mg/L, old water resource = 1.1-1.2 mg/L), and Gharehbolaq, Jolfa (current water resource = 0.35 mg/L and old water resource = 2.4 mg/L old source) were selected as low, medium, and high exposure to fluoride respectively. All village residents above 6 years old were visited by physician. Quality of water resources was determined by referring to the records archived and through conducting new analysis.
Results: Dental fluorosis was observed in 62.7 % of the people visited. In 31.5% of participants, fluorosis Grade 1 in 22.4 % of participants, fluorosis grade 2 in 7.7 % of participants, fluorosis grade 3 and finally fluorosis grade 4 was observed in 4 patients. Different levels of fluorosis were observed in residents of the villages of Gharebolaq, Nagharehkub, and Bashsizkooh (83.3%, 70.5 %, and 32.5 % respectively). There was a significant difference in prevalence of fluorosis between villages (P < 0.001). Fluorosis was observed in both permanent and temporary teeth. Mean cumulative fluoride index (MCFI) in people with and without fluorosis was 22660.2 and 4743.2 mg, respectively. There was a correlation between this index and fluorosis (R =0.413).
Conclusion: In all three villages studied, even Bashsizkooh, different grades of fluorosis were endemic. It is recommended that the responsible authorities take a  new measure and approach  for the intake of fluoride from drinking water.

!mso]> ject classid="clsid:38481807-CA0E-42D2-BF39-B33AF135CC4D" id=ieooui>

---

MicrosoftInternetExplorer4 Background and Objectives: Nitrate is one of the most groundwater pollutants in world. Reduction of nitrate to nitrite by microorganisms cause serious health hazards. Nitrate can be eliminated using either adsorbtion or reduction. In this study, we investigated the adsorption of nitate on zeolite and the feasibility of removal improvement using supported  zero valent nano iron on zeolite via the reduction process.
Materials and Methods: The study was done in two phases investigation the zeolite and modified zeolite with zero valent nano iron in nitrate removal from water. First, we determined the optimum pH and time then the effect of adsorbent and nitrate concentration was investigated in one factor at the time. The adsorption isotherm was calculated according to the optimum condition. The physical characteristics of adsorbents were determined using SEM and TEM.
Results: The morphology investigation of adsorbent showed that the particle size of supported zero valent nano iron on zeolite was approximately 30-50 nm in diameter. The best conditions were pH 5, contact time of 120 min and 15 g/L for zeolite, while pH 3, contact time of 50 min and 7.5 g/L for supported  zero valent nano iron on zeolite. The isotherm equations revealed that nitrate adsorption follows Langmiur in both cases.
Conclusion: The supported  zero valent nano iron on zeolite could be considered as a high potential adsorbent for nitrate because it has several adsorbent sites, and Fe⁰ as a function for nitrate reduction.

---

A MicrosoftInternetExplorer4 Background and Objectives: Colored wastewaters are known as one of the most important sources of environmental pollutants. Having toxic chemicals and aesthetic problems has made treatment of these wastewaters very crucial. So far a number of methods such as electrochemical treatment, coagulation and flocculation, and adsorption have been used for treatment of textile industries wastewater. Hence,  the efficiency of zero-valent iron powder in the presence of UV light and hydrogen peroxide to remove Acid Orange 7 and Reactive Black 5 from the synthetic solutions was investigated.
Materials and Methods: Conducting all experiments in a batch reactor, we examined different parameters including initial concentration of the color (25, 50, 75 mg/L), contact time (30,  60, 120 min), pH (3, 7, 11), the amount of iron powder (0.6, 1.3,  2  g/l), and hydrogen peroxide concentration (10, 15, 20  ml/l).
Result: The results showed that dye removal efficiency was increased by increasing contact time, the amount of iron powder and hydrogen peroxide concentration. On the other hand, with the increasing pH and initial concentration of dye, removal efficiency decreased in both AO7and RB5 dyes.
Conclusion: We found that the integrated ZVI/UV/H₂O₂ method has  high efficiency in removing azo dyes Acid Orange 7 and Reactive Black 5.

---

MicrosoftInternetExplorer4 Background and Objectives: Phenol is one of the most important organic chemicals presenting in water and other environments. It not only brings about hygienic problems but also results in forming 11 toxic priority pollutants in aqueous environments. Hence, the performance of electrocoagulation process using iron and aluminum sacrificial anodes was investigated for removal of phenol.
Materials and Methods: We used a glass tank in 1.56 L volume (effective volume 1 L) equipped with four iron and aluminum plate electrodes to do experiments (bipolar mode). The tank was filled with synthetic wastewater containing phenol in concentration of 5, 20, 40, and 70 mg/l and to follow the progress of the treatment, each sample was taken at 20 min intervals for up to 80 min. The percent of phenol removal was measured at pH 3, 5, 7, and 9 electrical potential range of 20, 40, and 60 volts and electrical conductivity of 1000, 1500, 2000, and 3000 µs/cm.
Results: It was found that the most effective removal capacities of phenol (95 and 98 %) could be achieved when the pH was kept 7 and 5 for iron and aluminum electrodes, reaction time  80 min, electrical conductivity 3000 µs/cm, initial concentration of phenol 5 mg/l, and electrical potential in the range of 20-60 V.
Conclusion: The method was found to be highly efficient and relatively fast compared with existing conventional techniques and also it can be concluded that the electrochemical process has the potential to be utilized for the cost-effective removal of phenol from water and wastewater.

---

Background and Objectives: On August 2012, two earthquakes measured 6 and 6.2 on the Richter scale took place in Eastern Azerbaijan province. Environmental Health Department is accounted as one of the main units for providing and supervising environmental sanitation services at the emergencies, therefore, the objective of this study was allocated to assess environmental health response performance in recent earthquake. Material and Methods: Through multi-stages stratified sampling, we selected 8 and 4 villages from the earthquake zones of Heris and Varzaghan respectively. The collecting data tools in this research were the WHO checklist in 7 categories, 14 subcategories, and 37 environmental health activities and also the minimum standards of Sphere Project checklist. The status of environmental health in each village was assessed using the mentioned checklists. This study was carried out with attendance of research team in earthquake zones 21 days after the occurrence of earthquake. Results: Among the 37 environmental health activities, 7 activities were the joint ones, which Environmental Health Department had to carry it out with the coordination of other related organizations. In other words, the environmental health has the supervising role in these activities. Totally, such activities had more nonconformities compared with the activities in which environmental health was administered as the main responder. The details of results have been expressed in the full text. Conclusion: Providing intra-sector coordination, prioritizing the needs of the affected population and considering the principles of community based management in the natural disaster are proposed as the recommendations of this study.

---

Background and Objectives: Nemone Tehran Poultry Slaughterhouse having an area of 13000 m² is located at District 3, Region 5 of Tehran Municipality and in Morad Abad Quarter .This study aimed at analysis the environmental impacts of the abovementioned slaughterhouse. For this purpose, we applied analytical hierarchy process (AHP) as one of the multiple criteria decision making methods (MCDM). Materials and Method: First, we determined the criteria and options required through analyzing the project impacts. Then, for final validity of criteria, we used experts questionnaire. Special vector technique through using the Expert Choice software was used in order to set priorities for criteria and options. Results: Analysis of the slaughterhouse effluent indicated that it can neither be discharged into the surface water and well nor suitable for irrigation and agricultural purposes. Noise evaluation showed that rate of noise measured is beyond the standard limits. The laboratory experiment results on air pollutants was lower than the standard level. Conclusion: The results indicated that from the pollution perspective in the slaughterhouse, wastewater weighted 0.497 is the primary preference and sound, air, and odour weighted 0.229, 0.136 and 0.080 are the subsequent preferences. Cultural and socioeconomical environment ranked hgiher relative to the chemical-physical environment and then biological environment. Finally, regarding to the main significant environmental problem of slaughterhouse (Wastewater), optimization of the slaughterhouse wastewater treatment system and constant monitoring of the external sewage quality is in priority.