Background: Aquaculture wastewater contains high levels of phosphate and nitrate. The reuse of this water requires standards beyond the secondary standards to eliminate more organic pollutants from aquaculture effluents. In this research, the removal of these pollutants from wastewater using Chlorella vulgaris and Fe3O4 nanoparticles in the reactor space was investigated.
Methods: This study was conducted on fish farms effluent in the laboratory system. For this purpose, a 5-L semi-industrial reactor with a mixer blade, porous plate, and a compressor was designed. Chlorella vulgaris samples were collected from the natural environment and cultured in the laboratory environment. Also, Fe3O4 nanoparticles were prepared from Iranian Nano Pishgaman Company to make the desired solution. During the experiment (3 weeks), samples were taken weekly (in one phase) from the effluent. Dissolved oxygen (DO), pH, nitrate (NO3), and phosphate (PO4) factors from the influent and effluent of the farms were measured. The statistical data were analyzed using SPSS version 21 and Excel 2013.
Results: The amounts of nitrate and phosphate were decreased by about 80.76 and 80.55% in the biological reactor, whereas these amounts were 70.52 and 70.48% in the nanoparticle reactor, respectively. Also, there were significant differences in the amounts of NO3 and PO4 between the control treatment and weekly treatment (P < 0.05).
Conclusion: Based on the results, both reactors were able to reduce nitrate and phosphate from aquaculture wastewater, but the efficiency of the biological reactor was higher than that of the nanoparticle reactor.

Background: Chlorination of wastewater effluent with high levels of residual organic matter has been suspected to the production of toxic and hazardous disinfection by-products (DBPs) including trihalomethane (THM) compounds.
Methods: In this study, two rapid techniques including dissolved oxygen depletion (DOD) and optical density (OD) bioassays were used to evaluate the chloroform toxicity of aqueous solution. The activated sludge was collected from aeration tank of a full-scale municipal wastewater treatment plant and used as a biological inoculum. In order to achieve an active and stabilized mixed culture of bacteria, the test cultures were transferred to a fresh nutrient broth culture media every day. The influence of chloroform on DOD and OD bioassays was examined at chloroform initial concentrations of 10-1000 μg/L.
Results: It was revealed that the application of chloroform at concentrations of 100 and 1000 μg/L showed moderate and extreme toxicity, respectively, and reduced bacterial activity. The estimated chemical concentration with 50% inhibition of bacterial activity for DOD and OD bioassays was 457 and 961 μg/L, respectively.
Conclusion: According to the results, the wastewater effluent should use bioassays in order to evaluate the effects of DBPs where the wastewater effluent is disinfected by chlorine compounds.

Background: Treatment of combined industrial wastewater from industrial parks is one of the most complex and difficult wastewater treatment processes. Also, the accuracy of biological models for the prediction of the performance of these processes has not been sufficiently evaluated. Therefore, in this study, the International Association on Water Quality (IAWQ(-Activated Sludge Model No. 1 (ASM1) was implemented for the Jey industrial park in Isfahan province, Iran.
Methods: The Jey IPWWTP process is a combination of anaerobic and aerobic biological processes. To evaluate the overall performance of IPWWTP, organic compounds, suspended solids, nutrients, attached biomass, and some operating parameters were measured during 6 months. Then, the biokinetic coefficients of aerobic processes were determined using Monod equations. Finally, the aerobic processes were modeled using ASM1 implemented in STOAT software.
Results: The values of the biokinetic coefficients K, Y, Ks, Kd, and µmax were calculated as 2.7d-, 0.34 mg VSS/mg COD, 133.36 mg/L COD, 0.03d-, and 0.93d-, respectively. Based on the default coefficients and conditions of the ASM model, the difference between the experiments and model prediction was about 2 to 98%. After calibrating the ASM model, the difference between the experiments and prediction in all parameters was reduced to less than 10%.
Conclusion: Investigations showed that the default coefficients and operation conditions of the ASM1 model do not have good predictability for complex industrial wastewaters and the outputs show a low accuracy compared to the experiments. After calibrating the kinetic coefficients and operating conditions, the model performance is acceptable and the predictions show a good agreement with the experiments.

Background: Tofu derived from processed soybeans is popular among the public, but its production has an unfavourable effect. After all, it produces liquid waste that causes quite high pollution because it contains quite high organic components. The present study aimed to reduce the content of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and ammonia (NH3) in the liquid waste of a tofu factory. The scope of this research is limited to reducing the content of BOD, COD, and NH3 using an anaerobic-aerobic biofilm aeration system.
Methods: This is an experimental study with a pre-post test only design and one group post-test design. The study population in this study is the tofu industry, and the sample in this study is partly water from the tofu waste. Sample examination was carried out at the Regional Health Laboratory of Jambi province, Indonesia.
Results: The results showed a decrease in BOD, COD, and NH3 after passing through a tofu waste treatment machine using anaerobic and aerobic biofilms with BOD, COD, and ammonia values of 64.6%, 49.6%, and 79.8%, respectively. Tofu waste treatment using anaerobic and aerobic biofilms can lower the temperature and increase the pH of the waste.
Conclusion: On the surface of the bioball used, the growth of the biofilm was found, and to increase the ability of the equipment, an initial treatment, such as filtration and sedimentation of waste, and reducing acidity with the help of quicklime was needed.