In the free water surface flow (FW-SF) constructed wetlands, a large number of microorganisms that live around the roots of plants create a suitable environment for wastewater treatment. To study the effect of Vetiver plant and sewage retention time in treatment efficiency of such systems, nine ponds in the Karoun sugarcane Agro-industrial located in the city of Shushtar was built. Units, in parallel with each other and each unit with length 3m, width 1m and height 0.8 meters. Continuously, agricultural wastewater from the washing process of sugarcane from December 2013 until May 2014 was established. Three of the units filled with soil and were transplanted with vetiver (S), three units were cultivated with vetiver on the floating platform (F) and three units were kept unplanted as control (C). The average BOD5 concentration of the wastewater entering the unit was 115±15.69 mg/l and retention times of experiments were 3, 5 and 7 days. During the experiment, the concentration of BOD5 per unit of input and output measurements was analyzed using SAS software. The results of the analysis showed significant differences between plant and non-plant systems, including retention times. The constructed wetland system with plant cultivated and the retention time of 7 days in May had highest value of the average removal rate equal to 68.48 percent. In other words, optimum conditions for maximum BOD5 removal rate of Karoun sugarcane Agro-industrial wastewater in floating constructed wetlands systems was with vetiver cultivated and in the retention time of 7 days.

Despite its universally wide use in water quality indices and evaluating the efficiency of wastewater treatment plants, chemical oxygen demand (COD) or biological oxygen demand (BOD5) analyses have disadvantages such as being imprecise, time-consuming, insensitive, as well as the production of hazardous wastes. Total organic carbon (TOC) will introduce as an alternative analysis, the relationship between BOD5, COD, and TOC has been investigated in this study. A total number of 216 samples were taken from three stations (kumait, Al Amara, and Al Majar Al Kabeer) in Tigris River, Maysan Province, Iraq. The sampling was on a monthly basis during a two-year period.  The tests were performed according to ASTM D7573 - 18ae1, ASTM D6238-98, and ASTM D125-06 for TOC, BOD5, and COD respectively at the Pollution Research Centre of the Al-Shatra Institute, the data were statistically analyzed using the SPSS program to predict a relationship between the COD or BOD5 and TOC. The analysis showed a good relationship concerning to a value of correlation coefficient, i.e., r = 0.93 or r = 0.94 between TOC and BOD5 or COD respectively, as well as the coefficient of determination, i.e., R2 = 0.91 or R2 = 0.92 between TOC and BOD5 or COD respectively. The validation of the suggested formulas has been tested using data from the Pollutant Centre in Al Shatra Institute for Shat al Gharaf River. The formulas gave reasonably acceptable values. It could be used in monitoring water quality and wastewater plants as a surrogate parameter to have pre-impression of the plant efficiency.

Shortage of water resources and renewable per capita in last 30 years is put Iran on crisis threshold. Wastewater reuse is one of the battle solutions for water shortage and prevents wastewater depletion and environmental pollution. Thus, a pilot scale experiment was carried out to evaluate an integrated anaerobic/aerobic treatment for removal of BOD5 and COD, also to reduction of hydraulic retention time by considering optimum removal efficiency. The pilot was an anaerobic/aerobic bioreactor type under continuous-feeding regime based on a central composite design. The pilot was studied in different retention time and aeration was carried out between 5-15 hours. According to different retention times for COD removal efficiency, 24 hours was selected as optimum hydraulic retention time, that it is comparable to those obtained for 48 hours and over in plant roughly and could remove COD and BOD in acceptable ranges, results showed that average removal efficiency for BOD5 were 63. 86 and 83. 99 percent in aerobic and anaerobic phases, respectively. The average removal efficiency for COD was 76. 5 and 74. 35 percent for anaerobic and aerobic sections, respectively. The average removal efficiency for BOD5 and COD in this integrated aerobic-anaerobic pilot 95. 24 and 94. 8 percent, respectively.

Introduction: As mechanical aerated lagoon for treatment of domestic wastewater has been just recently utilized in this province and our country and by taking into consideration that exact survey have not been done about efficiency of different unites. This study has been carried out to investigate wastewater treatment systems and find out the quality of effluent. Materials & Methods: This research has been carried out on integrated stabilization pond system (ISP) during four seasons of 1381. The study is a descriptive-sectional one. Composite samples were taken from raw wastewater & effluent from mechanical aerated & maturation pond each 15 days once (24 times every year each time 6 samples). The samples were examined based on standard method for analysis of water & wastewater in 1995. The data analyzed and were shown in different tables & diagrams. Results: The research results showed that the concentration of BOD5, COD, & TSS in raw wastewater was fairly high during fall and winter seasons. The average temperature of raw wastewater & weather in summer were respectively 5 & 15 degree centigrade more than fall season. This factor leads to the low efficiency of system in cold season because of slowing biological activities. Reduction of liter per capital per day (LPCD) is the main factor of increasing concentration of pollutant in raw wastewater. Comparison of efficiency of system in two seasons in spring & summer shown that reduction rate of pollutant in summer was higher than the rest of the year. The reduction of BOD5 & COD in summer was 8.5 - 9.5 percent higher than spring season. Discussion: Based on experiments the rate of BOD5, COD & TSS in effluent was 52, 97 & 93 mg/l, respectively, which need environmental protection organization to be used in agricultural & irrigation purposes. It is concluded that integrated stabilization pond (ISP) has required efficiency for treatment of domestic wastewater. However we need more investigation on lagoon system.

Reducing water resources and increasing demand for safe drinking water requires attention to water resources that can be returned to nature or can be used in industry or agriculture. In this regard, the use of optimal and effective methods for wastewater treatment and development is very important. In order to increase the efficiency of the wastewater treatment system and in order to reduce the pollution load of the effluent, it is very important to predict the quality of the treated effluent. In this research work, using genetic algorithm and neural network method, the effluent treatment system of Azerbaijan Pegah factory has been modeled in order to optimize the results using genetic algorithm and neural network method. The effluent treatment process should be carried out in order to anticipate the removal and disinfection of the remaining carbon materials and microbial contaminants according to the BOD5 and COD data that determine the quality of the effluent. The results show that the combination of the above two algorithms has been successful in predicting the output data compared to the actual data and there is an 87% matching of the data.

The discharge of wastewater from various industries such as petroleum and petrochemical, pollute water resources. The presence of these pollutants in water resources will cause disorders in the ecosystem and it has various risks to human health. The effluent usually contains organic matter, including phenol and its derivatives. In this study, three different types of reactors were used in the activated sludge process to study the biological removal of o-nitrophenol from the petrochemical industrial effluent. These reactors include Continuous Moving-Bed Sequencing Batch Reactor, Moving-Bed Sequencing Batch Reactor and conventional sequencing batch reactor. For this purpose, the operational indicators of each reactor were investigated and optimized. For MSBR, active sludge volume ratio (30%), aeration flowrate (18 L/min), operation time (4h), pH (7), filler to reactor volume ratio (4. 7 %) and SVI (89 ml/g) were considered. Also, For C-MSBR indicators such as initial volumetric flowrate (20 ml/min), aeration flowrate (12 L/min), filler to reactor volume ratio (5. 8 %) and SVI (98 ml/g) were optimized. As SBR is structurally similar to the other reactors, only initial volumetric flowrate was considered (40 ml/min) and based on the results, this reactor has better SVI (88 ml/g) than the other two reactors. Finally, based on the optimized parameters, percentage removal of ortho nitrophenol from a synthesized effluent, analogous to Karoon Petrochemical company effluent, was investigated by C-MSBR. In addition to o-nitrophenol, other chemicals such as Toluene and Benzene were also present. The results show the indicators including ortho nitrophenol percentage removal (84. 7%), Chemical Oxidation Demand (COD) (94%), Biochemical Oxidation Demand (94. 8%), BOD5/COD (0. 57) and SVI (74. 45 ml/g) comply with environmental standards and the treated effluent can be used in irrigation and agriculture by addition of one more processing step.

In present study, wastewater quality was evaluated applying multivariate analysis (PCA) and water quality index with respect to the Indian standards in the selected urban areas of Jaipur region, Rajasthan, India. Maximum average values of BOD5, TDS, chloride and fluoride were recorded as 21 mg/L, 1501 mg/L, 285.0 mg/L and 1.8 mg/L, respectively, along with metal concentration in order of  Zn (6.31 mg/L )> Fe (0.52 mg/L )> Mn (0.25 mg/L), Cu (0.16 mg/L)> Pb (0.11 mg/L)> Ni (0.02 mg/L).  PCA indicates four components extracted with a total variance of 78.48% from the water quality parameters. Wastewater Quality Index (WWQI) analysis emphasis level of pollution load at different sites which revealed 40% of the selected sites were inappropriate for reuse without treatment, however, 60% of the sites with moderate pollution load could be suitably reuse in agricultural and aquaculture. Findings of the present study conclude that multivariate analysis and wastewater quality index could be used as an effective tool for environmental monitoring, assessing, and categorizing wastewater to opt appropriate treatment, reuse and recycling options for sustainable wastewater management.