The impact of UV/H2O2 advanced oxidation on molecular size distribution of chromophoric natural organic matter

The impact of hydroxyl radical (*OH) on the molecular weight distribution of natural organic matter (NOM) was investigated. *OH was generated via the photolysis of hydrogen peroxide (H2O2) by ultraviolet (UV) radiation of 254 nm, also known as UV/ H2O2 advanced oxidation (AO). Additionally, the impact of combined membrane and UV/H2O2 treatment on the molecular weight distribution of NOM was studied. High performance size exclusion chromatography (HPSEC) was used to determine the apparent molecular weight (AMW) distribution of chromophoric NOM (CNOM). Prior to AO, 33% of the CNOM in the water had AMW greater than 1400 Da. Meanwhile, lower AMW CNOM made up smaller amounts of the CNOM, with CNOM of AMW less than 450 Da making up 5% of the total. Under the AO conditions typically applied in drinking water treatment applications, NOM was not mineralized but was partially oxidized resulting in significant reduction in aromaticity. *OH preferentially reacted with higher AMW CNOM and the fragmentation of high AMW CNOM led to the formation of smaller AMW CNOM. Ultrafiltration removed all CNOM greater than 1400 Da AMW and a large portion of other high AMW fractions. In the absence of high AMW CNOM, *OH reacted more readily with all AMW fractions leading to a reduction in concentration of most AMW fractions. Whereas *OH reacted nonspecifically with all AMW fractions, the reaction rate between *OH and CNOM was observed to be dependent on molecular size.     

Modelling of acrylic cut-pile carpet compression properties by means of expert systems based on carpet structural parameters

Abstract

Compression properties of carpet are a detrimental factor influencing carpet wear performance. In fact, carpet compression behavior determines carpet serviceability which in turn affects carpet appearance. Therefore, it is important to predict the carpet compression behavior in order to reduce the product cost. In this paper, a fuzzy logic model for prediction of compressional properties of acrylic cut-pile carpets is implemented in terms of the carpet structural parameters including carpet pile density, linear density of pile yarns and carpet pile height. In order to provide experimental data, six different acrylic cut-pile carpet samples fabricated by using six different acrylic spun pile yarns with yarn count of 18/3, 21/3, 27/3, 30/3, 33/3 and 36/3?Nm. Half of each provided carpet subjected to re-shearing process. All 12 carpet samples in two different cases (normal and reduced pile height) have been tested by standard carpet static and dynamic loading tests to measure thickness-loss as one of compression properties. Fuzzy logic model has been implemented and improved using genetic algorithm. Results show that correlation coefficients of model predictions with experimental values are 0.97, 0.98, 0.98 and 0.98 for carpet thickness-loss after low dynamic, high dynamic and static loading with short and long relaxation times, respectively. Also, linear regression trend between predicted and experimental values represented with a slope near to 1 and almost small bias (intercept). The result indicates that the developed fuzzy logic model is a reliable model predicting the acrylic cut-pile compression behavior.     

Integrated ozone and biotreatment of pulp mill effluent and changes in biodegradability and molecular weight distribution of organic compounds

The overall effectiveness of integrating ozonation with biological treatment on the biodegradability enhancement and recalcitrant organic matter (ROM) removal from pulp mill alkaline bleach plant effluent was investigated. Ozonation was performed in a semi-batch bubble column reactor at pH of 11 and 4.5. Batch biological treatment was conducted in shake flasks. Samples obtained during the treatments were monitored for BOD₅, COD, TOC, and molecular weight distribution. At an ozone dosage of 0.7-0.8 mg O₃/mL wastewater, integrated treatment showed about 30% higher TOC mineralization compared to individual ozonation or biotreatment. Ozone treatment enhanced the biodegradability of the effluent (monitored as 21% COD reduction and 13% BOD₅ enhancement), allowing for a higher removal of pollutants. The conversion of high molecular weight (HMW) to low molecular weight (LMW) compounds was an important factor in the overall biodegradability enhancement of the alkaline effluent. The overall biodegradability of the LMW compounds did not change over the course of ozonation, but it increased from 5% to 50% (measured as COD removal) for the HMW portion. Ozonation at pH of 11 was more effective than that at pH of 4.5 in terms of generating more biodegradable compounds.