Physical-chemical Treatment Processes Research Articles

Fate of antibiotics during membrane separation followed by physical-chemical treatment processes

Membrane separation technology has been widely utilised to obtain clean permeate and concentrated nutrients from biogas digested slurry. However, some antibiotics are frequently found in digested slurry. Antibiotic removal during the steps, including paper filtration (PF), hollow-fibre membrane ultrafiltration (HF), nanofiltration (NF) and reverse osmosis (RO), of combined membrane separation processing (CMP) remain poorly understood. Experiments were performed on a pilot-scale CMP plant to investigate antibiotic transport and rejection efficiencies in CMP products and analyse the antibiotic removal performances of additional treatments. Results showed average relative antibiotic rejection efficiencies of 50%, 83%, 28% and 14% for PF, HF, NF and RO during CMP, respectively. Each CMP product needed additional treatment for antibiotic removal. Antibiotic removal capacity followed the order of fine halloysite > P25 > activated charcoal > coarse halloysite. The average antibiotic removal rates for different CMP products ranged from 73.3% to 99.9%. But antibiotics can only be adsorbed by fine halloysite and must be degraded through other treatments, Thus, P25 has considerable practical importance for the removal of antibiotics, as antibiotics can be degraded during photocatalysis.

The coinage refractory wastewater treated by electrocatalytic-membrane process (ECMP) integrated with chemical- or electro-coagulation techniques

Some industrial wastewater containing complicated contents (e.g., heavy metals and organics) and extensive concentration-variation cannot be well-treated by physical-chemical treatment processes. In order to obtain the feasible electrochemical technique, an electrocatalytic-membrane process (ECMP) was established to treat such wastewater from a mint factory in Taiwan. Wastewater samples with pollutants of Cu2+, Ni2+ and chemical oxygen demand (COD) were categorized into three types based on pH and concentrations. The complexity of wastewater is attributed that a verity of chemical reagents and manufacturing methods are employed to produce different kind of coins. In this study, each type of wastewater was treated by the ECMP and integrated with other techniques to find out the appropriate procedures. Results indicate that the sole ECMP can effectively remove the Cu2+, Ni2+, and COD when the wastewater is with relatively low pH (around 3–5), low COD (around 50 mg L−1), and high concentration of heavy metals (Cu2+ concentration over 500 mg L−1). However, the ECMP should combine with pH-adjustment to effectively remove the Cu2+, Ni2+, and COD when the wastewater is with very low pH (close to 1), high COD (over 200 mg L−1), and high concentration of heavy metals. In addition, the ECMP has to link the electrocoagulation (ECG) to decrease the Cu2+, Ni2+, and COD concentration when the wastewater is with neutral pH (around 7), middle-level COD (around 130 mg L−1), and low concentration of heavy metals (Cu2+ concentration around 1.0 mg L−1). Accordingly, the ECMP integrated with other treatment processes gains potential to treat refractory wastewater.

Application of integrated MBR in a centralized WTP for a chemical industrial park: A case study in China

Abstract Wastewaters from chemical industries usually contain pollutants which are toxic and non-biodegradable. Treatment of chemical wastewaters is always a challenging topic in view of the stringent environmental regulations that have to be adhered to. Since 2014, the Chinese government has been continuously tightening the industrial wastewater (IWW) discharge standards, which requires improved quality of IWW effluent. This poses great challenges to the chemical industries in China, especially to many of the chemical industry clusters where the wastewaters usually contain more toxic and non-biodegradable contaminants. Membrane bioreactor (MBR) technology has been proved to be a reliable and cost-effective solution for the treatment of IWW. However, MBR alone could not effectively remove non-biodegradable organics, it needs to be integrated with advanced oxidization process and/or other physical-chemical treatment processes to improve the overall treatment efficiency. In this paper, studies on the performance of different integrated MBR processes in Industrial Wastewater Treatment Plant-A (IWTP-A) will be discussed, including Fenton + MBR, MBR + ozonation + biological aerated filter, and MBR + porous resin sorption.

A Floating Island Treatment System for the Removal of Phosphorus from Surface Waters

Abstract The goal of this project was to design, build, and test a pilot-scale floating modular treatment system for total phosphorus (TP) removal from nutrient-impaired lakes in central Florida, USA. The treatment system consisted of biological and physical–chemical treatment modules. First, investigations of prospective biological and physical–chemical treatment processes in mesocosms and in bench-scale experiments were conducted. Thirteen different mesocosms were constructed with a variety of substrates and combinations of macrophytes and tested for TP and orthophosphate ( PO 4 3 - ) removal efficiencies and potential areal removal rates. Bench-scale jar tests and column tests of seven types of absorptive media in addition to three commercial resins were conducted in order to test absorptive capacity. Once isolated process testing was complete, a floating island treatment system (FITS) was designed and deployed for eight months in a lake in central Florida. Phosphorus removal efficiencies of the mesocosm systems averaged about 40%–50%, providing an average uptake of 5.0 g·m−2·a−1 across all mesocosms. The best-performing mesocosms were a submerged aquatic vegetation (SAV) mesocosm and an algae scrubber (AGS), which removed 20 and 50 mg·m−2·d−1, respectively, for an average removal of 5.5 and 12.0 g·m−2·a−1 for the SAV and AGS systems, respectively. Of the absorptive media, the best performance was alum residual (AR), which reduced PO 4 3 - concentrations by about 75% after 5 min of contact time. Of the commercial resins tested, the PhosX resin was superior to the others, removing about 40% of phosphorus after 30 min and 60% after 60 min. Under baseline operation conditions during deployment, the FITS exhibited mean PO 4 3 - removal efficiencies of 53%; using the 50th and 90th percentile of PO 4 3 - removal during deployment, and the footprint of the FITS system, yielded efficiencies for the combined FITS system of 56% and 86%, respectively, and areal phosphorus removal rates between 8.9 and 16.5 g·m−2·a−1.

Microbial mats as a biological treatment approach for saline wastewaters: the case of produced water from hydraulic fracturing.

Treatment of produced water, i.e. wastewater from hydraulic fracturing, for reuse or final disposal is challenged by both high salinity and the presence of organic compounds. Organic compounds in produced water may foul physical-chemical treatment processes or support microbial corrosion, fouling, and sulfide release. Biological approaches have potential applications in produced water treatment, including reducing fouling of physical-chemical treatment processes and decreasing biological activity during produced water holding; however, conventional activated sludge treatments are intolerant of high salinity. In this study, a biofilm treatment approach using constructed microbial mats was evaluated for biodegradation performance, microbial community structure, and metabolic potential in both simulated and real produced water. Results demonstrated that engineered microbial mats are active at total dissolved solids (TDS) concentrations up to at least 100,000 mg/L, and experiments in real produced water showed a biodegradation capacity of 1.45 mg COD/gramwet-day at a TDS concentration of 91,351 mg/L. Additionally, microbial community and metagenomic analyses revealed an adaptive microbial community that shifted based upon the sample being treated and has the metabolic potential to degrade a wide array of contaminants, suggesting the potential of this approach to treat produced waters with varying composition.

Reductions in greenhouse gas (GHG) generation and energy consumption in wastewater treatment plants

Greenhouse gas (GHG) emission and energy consumption by on-site and off-site sources were estimated in two different wastewater treatment plants that used physical-chemical or biological processes for the removal of contaminants, and an anaerobic digester for sludge treatment. Physical-chemical treatment processes were used in the treatment plant of a locomotive repair factory that processed wastewater at 842 kg chemical oxygen demand per day. Approximately 80% of the total GHG emission was related to fossil fuel consumption for energy production. The emission of GHG was reduced by 14.5% with the recovery of biogas that was generated in the anaerobic digester and its further use as an energy source, replacing fossil fuels. The examined biological treatment system used three alternative process designs for the treatment of effluents from pulp and paper mills that processed wastewater at 2,000 kg biochemical oxygen demand per day. The three designs used aerobic, anaerobic, or hybrid aerobic/anaerobic biological processes for the removal of carbonaceous contaminants, and nitrification/denitrification processes for nitrogen removal. Without the recovery and use of biogas, the aerobic, anaerobic, and hybrid treatment systems generated 3,346, 6,554 and 7,056 kg CO(2)-equivalent/day, respectively, while the generated GHG was reduced to 3,152, 6,051, and 6,541 kg CO(2)-equivalent/day with biogas recovery. The recovery and use of biogas was shown to satisfy and exceed the energy needs of the three examined treatment plants. The reduction of operating temperature of the anaerobic digester and anaerobic reactor by 10°C reduced energy demands of the treatment plants by 35.1, 70.6 and 62.9% in the three examined treatment systems, respectively.

UV disinfection of Giardia lamblia cysts in water.

The human and animal pathogen Giardia lamblia is a waterborne risk to public health because the cysts are ubiquitous and persistent in water and wastewater, not completely removed by physical-chemical treatment processes, and relatively resistant to chemical disinfection. Given the recently recognized efficacy of UV irradiation against Cryptosporidium parvum oocysts, the inactivation of G. lamblia cysts in buffered saline water at pH 7.3 and room temperature by near monochromatic (254 nm) UV irradiation from low-pressure mercury vapor lamps was determined using a "collimated beam" exposure system. Reduction of G. lamblia infectivity for gerbils was very rapid and extensive, reaching a detection limit of >4 log within a dose of 10 JM-2. The ability of UV-irradiated G. lamblia cysts to repair UV-induced damage following typical drinking water and wastewater doses of 160 and 400 JM(-2) was also investigated using experimental protocols typical for bacterial and eucaryotic DNA repair under both light and dark conditions. The infectivity reduction of G. lamblia cysts at these UV doses remained unchanged after exposure to repair conditions. Therefore, no phenotypic evidence of either light or dark repair of DNA damage caused by LP UV irradiation of cysts was observed at the UV doses tested. We conclude that UV disinfection at practical doses achieves appreciable (much greater than 4 log) inactivation of G. lamblia cysts in water with no evidence of DNA repair leading to infectivity reactivation.

Aggregates of particles in dilute suspensions: Estimation of aggregate volume index and diameter

In physical-chemical treatment processes for waste water, the separation of the solids formed as hydroxides or carbonates can take place by sedimentation following precipitation. This is the basis for the elimination of metal compounds, which may also result in a reduction of the concentrations of organic material and phosphorus compounds in the waste waters. The settling rate of the solids depends on the solids concentration and the size and density of the aggregates formed. These properties can be obtained from batch sedimentation tests. When a batch test is carried out with flocculated suspensions containing a low concentration of solids, the upper supernatant—suspension interface is not always sharp. Nevertheless, the rate of rise of the sediment formed at the bottom can be measured. Taking into account the Kynch theory and other relationships proposed in the literature, the mean size and the ratio of water/solids in the aggregates can be deduced. The method explained in this paper has been applied to different suspensions with various flocculating agents. The aggregate diameter deduced is close to that observed directly for all the runs.