Enabling Water Reuse by Treatment of Reverse Osmosis Concentrate: The Promise of Constructed Wetlands

In Taiwan, more than 20% of the major rivers are mildly to heavily polluted by domestic, industrial, and agricultural wastewaters due to the low percentage of sewers connected to wastewater treatment plants. Thus, constructed or engineered wetlands have been adopted as the major alternatives to clean up polluted rivers. Constructed wetlands are also applied as the tertiary wastewater treatment systems for the wastewater polishment to meet water reuse standards with lower operational costs. The studied Kaoping River Rail Bridge Constructed Wetland (KRRBCW) is the largest constructed wetland in Taiwan. It is a multi-function wetland and is used for polluted creek water purification and secondary wastewater polishment before it is discharged into the Kaoping River. Although constructed wetlands are feasible for contaminated water treatment, wetland sediments are usually the sinks for organics and metals. In this study, water and sediment samples were collected from the major wetland basins in KRRBCW. The investigation results show that more than 97% of total coliforms (TC), 55% of biochemical oxygen demand (BOD), and 30% of nutrients [e.g. total nitrogen (TN), total phosphorus (TP)] were removed via the constructed wetland system. However, results from the sediment analyses show that wetland sediments contained high concentrations of metals (e.g. Cu, Fe, Zn, Cr, and Mn), organic contents (sediment oxygen demand = 1.7 to 7.6 g O2/m2 d), and nutrients (up to 18.7 g/kg of TN and 1.22 g/kg of TN). Thus, sediments should be excavated periodically to prevent the release the pollutants into the wetland system and causing the deterioration of wetland water quality. Results of polymerase chain reaction (PCR), denaturing gradient gel electrophoresis (DGGE), and nucleotide sequence analysis reveal that a variation in microbial diversity in the wetland systems was observed. Results from the DGGE analysis indicate that all sediment samples contained significant amounts of microbial ribospecies, which might contribute to the carbon degradation and nitrogen removal. Gradual disappearance of E. coli was also observed along the flow courses through natural attenuation mechanisms.

Download Full-text

Preliminary study on novel backwash cleaning for reverse osmosis fouling control in water reuse

Water Science & Technology Water Supply ◽

10.2166/ws.2010.418 ◽

2010 ◽

Vol 10 (3) ◽

pp. 296-301

Author(s):

Jian-Jun Qin ◽

Maung Htun Oo ◽

Kiran A. Kekre

Keyword(s):

Product Quality ◽

Reverse Osmosis ◽

Water Reuse ◽

High Salinity ◽

Full Scale ◽

Elapse Time ◽

Secondary Effluent ◽

Fouling Control ◽

Membrane Flux ◽

Preliminary Study

We have demonstrated a novel backwash cleaning technique of direct osmosis (DO)-high salinity (HS) for reverse osmosis (RO) fouling control in water reuse. An UF-RO pilot system was continuously (24-h) operated on site with the secondary effluent as the feed over 4 months. The RO plant was run at 75% recovery and at the membrane flux of 17 l m−2 h−1 (LMH) to simulate the full scale NEWater production when DO-HS treatment was conducted once per day and five times per week during the last two months. Permeability of RO membranes as a function of elapse time of the pilot operation was monitored and compared over different durations. Impact of DO-HS treatment on RO product quality in terms of TOC and conductivity was investigated. It was concluded that the DO-HS treatment preliminarily demonstrated a benefit to low RO fouling rate by 2.5–4 times in 30–60 days without interruption on RO operation and impact on RO product quality.

Download Full-text

Recycling of Reverse Osmosis Concentrates to the Membrane Bioreactor in the MBR-RO Process for Water Reuse: effect on mbr performances

Revue des sciences de l eau ◽

10.7202/1040057ar ◽

2017 ◽

Vol 30 (1) ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Thi Thu Nga Vu ◽

Manon Montaner ◽

Christelle Guigui

Keyword(s):

Organic Matter ◽

Reverse Osmosis ◽

Membrane Fouling ◽

Water Reuse ◽

High Performance ◽

Membrane Bioreactor ◽

Membrane System ◽

Size Exclusion ◽

Ro Concentrate ◽

The Impact

Wastewater effluents can be treated by an integrated membrane system combining membrane bioreactor (MBR) and reverse osmosis (RO) for effective removal of micropollutants in the field of high-quality water reuse. However, discharging the RO concentrate waste stream directly into the natural environment could lead to serious problems due to the toxic components contained in the concentrates (micropollutants, salts, organic matter). A possible solution could be the recirculation of RO concentrate waste to the MBR. However, such an operation should be studied in detail since the recirculation of non-biodegradable organic matter or high concentrations of salts and micropollutants could directly or indirectly contribute to MBR membrane fouling and modification of the biodegradation activity. In this context, the work reported here focused on the recirculation of such concentrates in an MBR, paying specific attention to MBR membrane fouling. Lab-scale experiments were performed on a continuous MBR-RO treatment line with RO concentrate recirculation. The main goal was to determine the recovery of the RO unit and of the global process that maintained good process performance in terms of biodegradation and MBR fouling. The results demonstrate that the impact of the toxic flow on activated sludge depends on the recovery of the RO step but the same trends were observed regardless of the organic matter and salt contents of the concentrates: the concentration of proteins increased slightly. Size-exclusion high performance liquid chromatography (HPLC-SEC) was employed to study the effects of RO concentrate on the production of protein-like soluble microbial products (SMPs) and demonstrated a significant peak of protein-like substances corresponding to 10-100 kDa and 100-1 000 kDa molecules in the supernatant. Thus a significant increase in the propensity for sludge fouling was observed, which could be attributed to the increased quantity of protein-like substances. Finally, the effect of the concentrate on sludge activity was studied and no significant effect was observed on biodegradation, indicating that the return of the concentrate to the MBR could be a good alternative.

Download Full-text

Boron as a Surrogate for N-Nitrosodimethylamine Rejection by Reverse Osmosis Membranes in Potable Water Reuse Applications

Environmental Science & Technology ◽

10.1021/es400732x ◽

2013 ◽

Vol 47 (12) ◽

pp. 6425-6430 ◽

Cited By ~ 11

Author(s):

Kha L. Tu ◽

Takahiro Fujioka ◽

Stuart J. Khan ◽

Yvan Poussade ◽

Annalie Roux ◽

...

Keyword(s):

Reverse Osmosis ◽

Water Reuse ◽

Potable Water ◽

Reverse Osmosis Membranes

Download Full-text

Vacuum evaporation and reverse osmosis treatment of process wastewaters containing surfactant material: COD reduction and water reuse

Clean Technologies and Environmental Policy ◽

10.1007/s10098-019-01673-5 ◽

2019 ◽

Vol 21 (4) ◽

pp. 861-870 ◽

Cited By ~ 6

Author(s):

Eniko Haaz ◽

Daniel Fozer ◽

Tibor Nagy ◽

Nora Valentinyi ◽

Anita Andre ◽

...

Keyword(s):

Reverse Osmosis ◽

Water Reuse ◽

Vacuum Evaporation ◽

Cod Reduction ◽

Surfactant Material

Download Full-text

Forward osmosis for the treatment of reverse osmosis concentrate from water reclamation: process performance and fouling control

Water Science & Technology ◽

10.2166/wst.2014.138 ◽

2014 ◽

Vol 69 (12) ◽

pp. 2431-2437 ◽

Cited By ~ 19

Author(s):

C. Kazner ◽

S. Jamil ◽

S. Phuntsho ◽

H. K. Shon ◽

T. Wintgens ◽

...

Keyword(s):

Reverse Osmosis ◽

Water Reuse ◽

Membrane Filtration ◽

Inorganic Compounds ◽

Forward Osmosis ◽

Building Blocks ◽

Water Recovery ◽

Liquid Discharge ◽

Quality Water ◽

A Minor

While high quality water reuse based on dual membrane filtration (membrane filtration or ultrafiltration, followed by reverse osmosis) is expected to be progressively applied, treatment and sustainable management of the produced reverse osmosis concentrate (ROC) are still important issues. Forward osmosis (FO) is a promising technology for maximising water recovery and further dewatering ROC so that zero liquid discharge is produced. Elevated concentrations of organic and inorganic compounds may act as potential foulants of the concentrate desalting system, in that they consist of, for example, FO and a subsequent crystallizer. The present study investigated conditions under which the FO system can serve as concentration phase with the focus on its fouling propensity using model foulants and real ROC. Bulk organics from ROC consisted mainly of humic acids (HA) and building blocks since wastewater-derived biopolymers were retained by membrane filtration or ultrafiltration. Organic fouling of the FO system by ROC-derived bulk organics was low. HA was only adsorbed moderately at about 7% of the initial concentration, causing a minor flux decline of about 2–4%. However, scaling was a major impediment to this process if not properly controlled, for instance by pH adjustment or softening.

Download Full-text