A comparative study on the performance of NSFWQIm and IRWQIsc in water quality assessment of Sefidroud River in northern Iran.

Local water quality indices (WQIs) are usually developed by modifying internationally recognized indices, which are considered reference index. In previous works on WQIs, the performance of local and reference indices has not been compared with each other. Therefore, the question crosses the mind whether using local or international indicators individually can show all qualitative aspects of a water resource. In this study, it was aimed to make this comparison between NSFWQIm (National Sanitation Foundation Water Quality Index) as the reference index and IRWQIsc (Iranian Water Quality Index for Surface Water Resource-Conventional Parameters) as the local one through a case study (Sefidroud River in northern Iran). Based on the results, the indices' performance in representing the seasonal and spatial fluctuations of the river water quality was almost similar. However, the water quality scores obtained by the two indices were somewhat different. Based on NSFWQIm, the average water quality score of the river was about 49.0, by which the water was categorized in "bad" class, while IRWQIsc represented an average score of 56.1, which corresponds to "fairly good" class. Therefore, NSFWQIm identified the water quality with stricter criteria than IRWQIsc, regarding the public health. On the other hand, according to relative standard deviations (0.17 for NSFWQIm, 0.21 for IRWQIsc) of the obtained water qualities, IRWQIsc better distinguished between high and low water qualities of the river. Accordingly, in order to better interpret the quality conditions of surface water resources in Iran, it is necessary to use both indices since NSFWQIm (reference index) attracts attention to stricter international standards and requirements, while IRWQIsc (local index) causes more focus on seasons or locations with the worst water quality.

Operation of integrated sequencing batch membrane bioreactor treating dye-containing wastewater at different SRTs: study of overall performance and fouling behavior.

The main aim of the present work was to study the overall performance and the fouling behavior of the integrated sequencing batch membrane bioreactor (SBMBR) treating synthetic dye-containing wastewater at different sludge retention times (SRTs) of 10, 40, and 160 days. For this reason, the removal efficiencies of color and chemical oxygen demand (COD) and the membrane fouling rates as well as the main sludge characteristics including extracellular polymeric substances (EPS), soluble microbial products (SMP), particle size distribution (PSD), and apparent viscosity were evaluated during the operation time of three SBMBRs. According to the obtained results, the decolorization efficiency was found to increase with increasing the SRT while the COD removal efficiency was similarly high (94-97%) in all SBMBRs regardless of SRT change. The rate of rise of transmembrane pressure (TMP) was much lower in the SBMBR operating at SRT of 160 days compared with the two other SBMBRs. Cake development on the membrane surface was recognized as the predominant fouling mechanism in three SBMBRs. Among the stated sludge properties, specific EPS and uniformity coefficient of the particle size distribution were suggested to be the controlling factors of the membrane fouling rate in three SBMBRs. During the operation at prolonged SRT (160 days in this study), better decolorization efficiency and lower biofouling rate were obtained in SBMBR system.

Coagulation/flocculation of dye-containing solutions using polyaluminium chloride and alum.

This study aims to compare the performance of Polyaluminium Chloride (PAC) and alum as coagulants to remove a specific type of dye (Acid Blue 292 (AB292)) from dye-containing solution. For this purpose, the influence of pH, coagulant dosage, coagulant aids (kaolinite and bentonite), and initial dye concentration on dye removal efficiency were examined. According to the results, removal of AB292 was absolutely dependent on the pH variations. The maximum dye removal occurred when pH was 7 and 5 for PAC and alum, respectively. Both coagulants efficiently removed the dye (about 85%) with a relatively low dosage (40 mg/l) in their optimum pH range. By adding kaolinite as a coagulant aid, the removal efficiencies tended to increase, especially for lower dosages of PAC and alum. With the increase of initial dye concentration, PAC and alum represented different behaviors. In the case of PAC, Q (the amount of the removed dye per unit mass of coagulant) increased at first and reached to a maximum value, 2.1 mg dye/mg PAC, and then decreased rapidly. While for alum, Q steadily increased with the increase of dye concentration and reached to 2.8 mg dye/mg alum. No reduction of Q occurred for alum with the increase of dye concentration in the range of 25-250 mg/l.