Pin Zhao

Effect of six kinds of scale inhibitors on calcium carbonate precipitation in high salinity wastewater at high temperatures

Precipitation of calcium carbonate (CaCO3) scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect of six kinds of commercial scale inhibitors and screened out the best one (scale inhibitor SQ-1211) to investigate its scale inhibition performance in highly saline conditions at high temperature through static scale inhibition tests. The influences of scale inhibitor dosage, temperature, heating time and pH on the inhibition efficiency of the optimal scale inhibitor were investigated. The morphologies and crystal structures of the precipitates were characterized by Scanning Electron Microscopy and X-ray Diffraction analysis. Results showed that the scale inhibition efficiency of the optimal scale inhibitor decreased with the increase of the reaction temperature. When the concentration of Ca2+ was 1600 mg/L, the scale inhibition rate could reach 90.7% at 80°C at pH8. The optimal scale inhibitor could effectively retard scaling at high temperature. In the presence of the optimal scale inhibitor, the main crystal structure of CaCO3 changed from calcite to aragonite.

Enhanced phosphorus and ciprofloxacin removal in a modified BAF system by configuring Fe-C micro electrolysis: Investigation on pollutants removal and degradation mechanisms

A modified biological aerated filter (BAF) system configured Fe-C micro electrolysis was applied to enhance phosphorus and ciprofloxacin (CIP) removal. A novel sludge ceramic and sintering ferric-carbon ceramic (SFC) were separately packed into a lab-scale BAF and Fe-C micro electrolysis reactor. The BAF and Fe-C micro electrolysis coupled system was operated about 230days. The enhancement of phosphorus and ciprofloxacin removals by Fe-C micro electrolysis, the degradation mechanisms of CIP and the variations of microbial population were investigated. The removal efficiencies of chemical oxygen demand (CODcr), ammonia (NH4-N), total phosphorus (TP) and CIP reached about 95%, 95%, 80% and 85% in the combined process, respectively. Configuring Fe-C micro electrolysis significantly enhanced phosphorus and CIP removal, whereas had no promotion on N removal. Four main degradation pathways were proposed according to the LC-MS analysis. More than 12 degradation products were detected through the treatment of Fe-C micro electrolysis and only 3 biodegraded products with low concentration were identified in BAF effluent. The high-throughput sequencing analysis showed that the microbial community changed a lot under CIP pressure. The relative abundance of Sphingomonadaceae, Xanthomonadaceae, Bradyrhizobium, Helicobacter and Pseudomonas increased with CIP influent. This study provides a promising process in CIP wastewater treatment.

Fatty acid fouling of forward osmosis membrane：Effects of pH,calcium,membrane orientation,initial permeate flux and foulant composition

Octanoic acid (OA) was selected to represent fatty acids in effluent organic matter (EOM). The effects of feed solution (FS) properties, membrane orientation and initial permeate flux on OA fouling in forward osmosis (FO) were investigated. The undissociated OA formed a cake layer quickly and caused the water flux to decline significantly in the initial 0.5hr at unadjusted pH3.56; while the fully dissociated OA behaved as an anionic surfactant and promoted the water permeation at an elevated pH of 9.00. Moreover, except at the initial stage, the sudden decline of water flux (meaning the occurrence of severe membrane fouling) occurred in two conditions: 1. 0.5mmol/L Ca(2+), active layer facing draw solution (AL-DS) and 1.5mol/L NaCl (DS); 2. No Ca(2+), active layer-facing FS (AL-FS) and 4mol/L NaCl (DS). This demonstrated that cake layer compaction or pore blocking occurred only when enough foulants were absorbed into the membrane surface, and the water permeation was high enough to compact the deposit inside the porous substrate. Furthermore, bovine serum albumin (BSA) was selected as a co-foulant. The water flux of both co-foulants was between the fluxes obtained separately for the two foulants at pH3.56, and larger than the two values at pH9.00. This manifested that, at pH3.56, BSA alleviated the effect of the cake layer caused by OA, and OA enhanced BSA fouling simultaneously; while at pH9.00, the mutual effects of OA and BSA eased the membrane fouling.

Preparation of wheat straw-supported Nanoscale Zero-Valent Iron and its removal performance on ciprofloxacin

Wheat straw-supported Nanoscale Zero-Valent Iron particles (WS-NZVI) were successfully synthesized, which were used for Ciprofloxacin hydrochloride (CIP) removal in simulation wastewater. The structure, chemical composition and micro-morphology of WS-NZVI and Nanoscale Zero-Valent Iron (NZVI) were characterized by scanning electron microscopy analysis (SEM), X-ray diffraction (XRD), as well as the Fourier Transformed IR spectra (FT-IR). XRD results proved the existence of Fe°, and SEM images indicated that the agglomeration of NZVI was effectively inhibited when loaded on wheat straw. Besides, the effects of initial solution pH, CIP concentration, adsorbents dosage and contacting time on the removal efficiency of CIP by WS-NZVI and NZVI were investigated. The experimental results showed that, compared with NZVI and wheat straw, WS-NZVI possessed higher removal efficiency for CIP, and the maximum removal capacity of CIP by WS-NZVI was 363.63 mg g-1 (25 °C). Furthermore, WS-NZVI was suitable for wider pH range (pH = 4-10) in comparison with NZVI. For the WS-NZVI, the kinetic was better fitted with pseudo-second-order equation, rather than pseudo-first-order equation. The Mass spectrometry (MS) analysis deduced that the degradation reaction mainly occurred on quinolone groups piperazinyl ring. Therefore, it is feasible that using wheat straw as a support material to enhance the performance of NZVI, and the synthesized WS-NZVI has a potential in the organic compounds elimination because of its redox reaction activity.

Fouling of forward osmosis membrane by protein (BSA): effects of pH, calcium, ionic strength, initial permeate flux, membrane orientation and foulant composition

AbstractIn this study, bovine serum albumin (BSA) was selected to represent proteins of secondary wastewater effluent. The role of various physical and chemical interactions, such as calcium concentration, ionic strength, solution pH, feed foulant composition, initial permeate flux, and membrane orientation, in BSA fouling of forward osmosis (FO) membranes was investigated. Fouling experiments showed that membrane fouling by BSA was enhanced with increasing calcium concentration and ionic strength. The former was mainly due to the complexes formed by the interaction of Ca2+ and carboxylic functional groups of BSA, and the latter resulted from the decreasing electrostatic repulsion among BSA molecules and between BSA molecules and membrane. Moreover, FO membrane fouling became much more significant at solution pH 4.7 (the BSA isoelectric point), where BSA molecules were neutrally charged and had no electrostatic repulsion among themselves. It was also demonstrated that the presence of alginate (a model pol...

Exploration of polyepoxysuccinic acid as a novel draw solution in the forward osmosis process

Polyepoxysuccinic acid (PESA) is a green corrosion scale inhibitor. When PESA is used for wastewater desalination in the forward osmosis (FO) process, the diluted PESA solution could be used for cooling systems. In our investigation, the effects of membrane orientation, temperature and flow rate on FO performance are studied using PESA as a draw solute. The results show that the effect of temperature on water flux is obvious, but the water flux increase is higher from 25 °C to 35 °C than that from 35 °C to 45 °C. Compared to the FO mode, the water flux increases faster in the pressure-retarded osmosis mode (PRO mode) at high flow rate due to the reduction of concentrative internal concentration polarization (CICP). Compared with polyaspartic acid (PASP) and NaCl, the water flux of PESA is the lowest under the same conditions. However, PESA has the lowest specific reverse solute flux (Js/Jw) at both membrane orientations. For example in the FO mode this value is 0.46 g L−1, whereas that of NaCl and PASP is 1.12 and 0.74 g L−1, respectively. This means that PESA has lower loss to the feed side than NaCl and PASP in the FO process, which greatly reduces the replenishment cost of the draw solute. The use of PESA as the draw solute in the FO process to treat dyeing water has the advantages of stable water flux (within 20 min), high dye rejection (nearly 1) and reversible membrane fouling (restored to 97%). The nanofiltration (NF) process indicates the good performance of PESA recovery with a high specific water flux (0.94 LMH per bar) and rejection rate (97.8%). Thus, the overall performance of PESA demonstrates that it is a promising draw solute.