Suspended Solids In Wastewater Research Articles

First determination of C 60 and C 70 fullerenes and N-methylfulleropyrrolidine C 60 on the suspended material of wastewater effluents by liquid chromatography hybrid quadrupole linear ion trap tandem mass spectrometry

The increasing use and production of carbon-based nanoparticles demands for new analytical approaches able to achieve sensitivities in the low ng/L range in order to assess their presence in environmental samples. This paper describes development, optimization and validation of a novel method for the analysis of C 60 and, C 70 fullerenes and N-methylfulleropyrrolidine C 60 in the environment. The method relies on ultrasonication extraction from suspended solids in wastewater, followed by liquid chromatography (LC) coupled to a hybrid triple quadrupole linear ion trap mass spectrometry (QqLIT-MS) for trace quantification. Recoveries obtained were generally higher than 60% for both surface water and wastewaters. The overall variability of the method was below 15%, for the three fullerenes and all tested matrices: ultra-pure water, surface water and wastewater. For the effluents of wastewater treatment plants the method quantification limits (MQL) ranged from 0.2 to 1 ng/L. The precision of the method, calculated as relative standard deviation (RSD), ranged from 1% to 2% and from 5% to 9% for intra and inter-day analysis, respectively. The developed analytical method was applied to the analysis of fullerenes in the effluents of 22 wastewater treatment plants in Catalonia (NE of Spain). 50% of the analyzed samples contained fullerenes, nine of them in the μg/L concentration range. This work constitutes the first report on the occurrence of fullerenes in suspended solids of wastewater effluents highlighting the need of nanotechnologies residues assessment for risk evaluation of nanoparticles in the environment.

Evaluation of Second‐Generation Multistage Wastewater Treatment System for the Removal of Malodors from Liquid Swine Waste

Wastewater quality and malodors in a second generation implementation of environmentally superior technology (EST) were monitored over three cycles of pig (Sus scrofa) production and 15 mo. The wastewater treatment system consisted of three modules: solids separation, biological N removal, and P recovery/wastewater disinfection. While approximately more than 90% of the wastewater suspended solids were removed in the first stage of treatment, little reduction in malodorous compounds occurred, indicating that malodors largely remained with the liquid waste stream. The greatest improvements in wastewater quality occurred in the N treatment module where ammonium was removed through nitrification/denitrification processes: there was more than 99% reduction in aromatic malodorous compounds (e.g., p-cresol, skatole) and almost 90% reduction in volatile fatty acids (e.g., propanoate and butanoate) in N module effluent as compared to raw flushed manure. The system performed consistently well in wastewater odor removal, even during the first cycle of livestock production when system performance was being optimized. These findings showed that the combination of the processes of solids removal and biological N treatment into a practical treatment system can be very effective in reducing malodors from livestock wastewater.

A New Process for the Management of Olive Oil Mill Waste Water and Recovery of Natural Antioxidants

The high polyphenol content of the wastewater is the major environmental problem caused by the olive mills. A pilot scale system for the treatment of the olive oil mills wastewater was developed aiming at the recovery of high added value-contained polyphenols and the reduction of the environmental problems. The treatment system consists of three main successive sections: The first one includes successive filtration stages aiming at the gradual reduction of the wastewater suspended solids up to a limit of 25 microm. The second section includes passing of the filtered wastewater through a series of adsorbent resins (XAD16 and XAD7HP) in order to achieve the de-odoring and decolorization of the wastewater and the removal/ recovery of the polyphenol and lactone content. The third section of the procedure includes the thermal evaporation and recovery of the organic solvents mixture, which has been used in the resin regeneration process, and finally the separation of the polyphenols and other organic substance contents using fast centrifuge partition chromatography. The final outcome of the whole procedure is (i) an odorless yellowish wastewater with a 99.99% reduced content in polyphenols and 98% reduced COD, (ii) an extract rich in polyphenols and lactones with high antioxidant activity and high added value, (iii) an extract containing the coloring substances of the olive fruit, and (iv) pure hydroxytyrosol.

A preliminary study on electrically enhanced crossflow microfiltration of CMP (chemical-mechanical polishing) wastewater

Chemical-mechanical polishing (CMP) is currently one of the main technologies used by wafer plants in the semiconductor industry. Normally, a large amount of de-ionized water should be used to wash out the abrasives adhered to the surface of wafers during the grinding process. Therefore, CMP wastewater not only has a great quantity but also contains very small size of suspended solids. Generally, these suspended solids would not settle. This phenomenon results in a low visibility of CMP wastewater. To solve this problem, a study on electrically enhanced crossflow microfiltration of CMP wastewater was conducted. Normally, the membrane of traditional dead-end filtration is easily blocked by the filter cake resulting in a small flux of filtrate. Therefore, the form of crossflow filtration (CFF) is used to reduce the blocking of the membrane. Furthermore, if CFF is accompanied by an external electric field, the negatively charged suspended solids in wastewater would move toward the positive electrode. Meanwhile, the flux of filtrate would increase. In this investigation, CMP wastewater was obtained from a wafer plant and characterized by various standard methods. Before testing, the CMP wastewater was pre-filtered using a 1.2 microm pore size filter. Then it was operated by a crossflow microfiltration (0.1 microm pore size) system under an appropriate crossflow velocity, filtration pressure, and electric potential. The filtrate was also characterized by various standard methods. Experimental results show that the filtrate has a turbidity of zero value. Thus, the filtrate could be reused for other purposes. However, the suspended solids of the CMP wastewater would be concentrated by this method. Therefore, the recovery of the suspended solids would be worth considering.

Wastewater suspended solids study by optical methods

The aim of the paper is to compare two optical methods (UV spectrophotometry and laser granulometry) for a better knowledge of the behaviour of wastewater suspended solids. The first one, based on UV spectrophotometry, is used for the estimation of solids concentration and nature in water and wastewater with the help of an advanced exploitation method of UV spectra. But the interpretation of UV spectra, in presence of a very wide size distribution of solids is not always easy, because of the different phenomena responsible of light diffusion. The second method, more classical, allows to characterise the size distribution of particles.

The performance of the waste stabilisation pond system at Boujaad, Morocco

The wastewater stabilisation ponds system of the city of Boujaâd was constructed and put into operation in 1992. The two main objectives of this plant are the prevention of pollution of water resources and the environment by means of wastewater discharges as well as the saving of fresh water by means of reuse of treated wastewater for irrigation purposes. Within the period of March 1997 to March 1998 a comprehensive analysis campaign of both the raw and the treated wastewater at a number of different sampling points has been carried out in order to evaluate the treatment efficiency of this wastewater treatment plant.The results of these investigations showed an average raw wastewater flow of 1600 m3/d, which is well below the design flow of 2500 m3/d. With respect to the physico-chemical treated wastewater quality and in comparison with the French treated wastewater standards (1980) these results indicated that 90 % of the wastewater samples showed BOD5-figures below the quoted French standard, whereas 83 % of the samples showed COD-figures above the corresponding French treated wastewater standard. With average treated wastewater suspended solids contents of 56 mg/l the suspended solids removal rate has been determined as being in the range of 65 %. If compared to the anticipated Moroccan wastewater standards for direct wastewater discharge into receiving water bodies as stipulated in the Moroccan Standards Project the obtained wastewater analysis results showed COD- and BOD5 values below these foreseen Moroccan wastewater discharge standards. The analysis results of SS, TKN and total phosphorus (Ptot) showed figures slightly above these Moroccan standards. In view of the microbiological wastewater characteristics the treated effluents of the Boujaâd WSP respond to the WHO directive with respect to wastewater to be used for restricted irrigation (category B). Taking into consideration the CEC directive for wastewater generated by wastewater treatment plants and discharged to the environment, the efficiency of the Boujaâd WSP is relatively low with respect to the SS-removal, the removal of organic matter (expressed by BOD5 and COD) as well as the removal of nutrients (expressed by TKN and Ptot). This relatively low efficiency might basically be caused by the already highly diluted incoming raw wastewater, which again is caused by the effect of significant infiltration of groundwater into the sewerage network. Besides the evaluation of the overall treatment efficiency, detailed investigations of the performance of individual ponds have been carried out as well.

Study on the performance of the wastewater stabilisation pond of Boujaâd, Morocco

The wastewater stabilisation ponds system of the city of Boujaâd was constructed and put into operation in 1992. The main objectives of this plant are to prevent pollution of water resources and the environment by wastewater discharges, and to save fresh water by reusing treated wastewater for irrigation purposes. Within the period March 1997–March 1998 a comprehensive analysis of both the raw and the treated wastewater at a number of different sampling points was carried out in order to evaluate the treatment efficiency of the plant. The results of these investigations showed an average raw wastewater flow of 1600 m 3 /d, which is well below the design flow of 2500 m 3 /d. With average treated wastewater suspended solids (SS) content of 56 mg/l the SS removal rate has been determined to be about 65%. If compared to the anticipated Moroccan wastewater standards for direct wastewater discharge into receiving water bodies as stipulated in the anticipated Moroccan Standards (AMS 1996) the wastewater analysis results showed COD and BOD 5 values below these foreseen Moroccan wastewater discharge standards. The analysis results of SS, TKN and total phosphorous (P tot ) were slightly above these Moroccan standards. In view of the microbiological wastewater characteristics the treated effluents of the Boujaâd wastewater stabilisation ponds (WSP) respond to the WHO directive with respect to wastewater to be used for unrestricted irrigation (category A). Taking into consideration the CEC directive for wastewater generated by wastewater treatment plants and discharged to the environment, the efficiency of the Boujaâd WSP is relatively low with respect to SS removal, the removal of organic matter (expressed by BOD 5 and COD) and the removal of nutrients (expressed by TKN and P tot ). This relatively low efficiency may be caused by the already highly diluted incoming raw wastewater, which again is caused by the effect of significant infiltration of groundwater into the sewerage network.

Input and distribution of alkylphenol polyethoxylates in a stratified estuary

The behaviour and fate of nonylphenol polyethoxylate surfactants (NPnEO) in the Krka River estuary were studied during 1990–1991. The study comprised determination of NPnEO input via municipal wastewaters and their subsequent distribution in the water column of the estuary. All quantitative determinations were performed by high-performance liquid chromatography using both normal-phase and reversed-phase systems. The concentrations of NPnEO in untreated municipal wastewaters varied in a wide range of 70 to 2960 μg/l. The oligomer distribution in all of the analysed wastewater samples was rather uniform characterised by a maximum at NP10EO which indicated heavy-duty detergents as the predominant source of NPnEO in the investigated area. Hydrophobic partitioning between dissolved and solid phase was found to play a significant role in wastewaters, as indicated by a relatively high percentage (6–60%) of NPnEO associated with wastewater suspended solids and by different oligomer distribution patterns in the two phases. The most important features of the NPnEO distribution in the estuary were: (1) exponential decrease of concentrations with increasing distance from sewage outlets, and (2) a rather complex vertical distribution pattern which reflected the basic hydrographic properties of this strongly stratified estuary. An efficient initial dilution was found to be the chief mechanism that was responsible for rather low NPnEO concentrations in estuarine waters. However, significant concentration differences were observed between the brackish water layer (1.1–6 μg/l) and saline water layers (0.1–0.7 μg/l). This suggested that the wastewater plume spreads into the estuary predominantly in the brackish water layer while the underlying saline water layer remains much less affected. However, NPnEO concentration maxima were observed at the two estuarine phase boundaries: air-brackish water (17 μg/l) and brackish water-saline water (9 μg/l). Relatively small changes of the oligomer distribution pattern in the water column, compared to that originally found in wastewaters, indicated that biodegradation played only a limited role as the mass balance determining process in the estuary.

Examination of Bacterial Characteristics of Anaerobic Membrane Bioreactors in Three Pilot-Scale Plants for Treating Low-Strength Wastewater by Application of the Colony-Forming-Curve Analysis Method

Characteristic sludge ecosystems arising in anaerobic membrane bioreactors of three pilot-scale plants treating low-strength (less than 1 g of biological oxygen demand per liter) sewage or soybean-processing wastewater were examined by analysis of the colony-forming-curves (CFC) obtained by counting colonies at suitable intervals. The wastewaters, containing high amounts of suspended solids (SS) (SS/chemical oxygen demand ratio, 0.51 to 0.80), were treated by using two types of bioreactors: (i) a hydrolyzation reactor for solubilization and acidification of SS in wastewater and (ii) a methane fermentation reactor for producing methane. The colony counts for the two sewage treatment plants continued to increase even after 3 weeks of incubation, whereas those for soybean-processing wastewater reached an approximately constant level within 3 weeks of incubation. The CFCs were analyzed by correlating the rate of colony appearance on roll tubes with the physiological types of bacteria present in the bioreactors. It was found that there were large numbers of slow-colony-forming anaerobic bacteria within the bioreactors and that the viable populations consisted of a few groups with different growth rates. It is considered that the slow-growing colonies appearing after 10 days of incubation were the dominant microflora in the sewage treated by hydrolyzation reactors. In particular, highly concentrated sludge (30.0 g of mixed-liquor volatile SS per liter) retained by the membrane separation module contained a large number of such bacteria. Slow-growing colonies of these bacteria could be counted by using a sludge extract medium prepared from only the supernatant of autoclaved sludge. In addition, the highest colony counts were almost always obtained with the sludge extract medium, meaning that most of the anaerobic bacteria in these sludges have complex nutrient requirements for growth. This report also indicates the usefulness of application of the CFC analysis method to the study of bacterial populations of anaerobic treatment systems.

Design Considerations for a Nitrification-Denitrification Process Using Two Fixed-Bed Reactors in Series

This paper concerns design considerations (kinetics and hydraulic criteria) for a biological nitrification-denitrification attached culture process for sewage treatment. The treatment system is composed of two submerged filters. The first one, an anoxic reactor, denitrifies and retains wastewater suspended solids. The second one oxidizes organic carbon and ammonia nitrogen. It was found that the main parameter for the system is the recycle ratio since it sets the real hydraulic detention time in reactors and determines the quantity of nitrogen available to the denitrification process.

Dissolved air flotation for abattoir wastewater

The performance of laboratory-scale dissolved air flotation plants treating abattoir wastewater has been measured for saturator pressures from 100 to 500 kPa, wastewater suspended solids concentrations from 170 to 2100 mg 1 −1 and air-to-solids ratios from 0 to 0.17. Maximum removal efficiencies for chemical oxygen demand, suspended solids and fat were 70, 50 and 95% respectively, at high wastewater suspended solids contents and high air-to-solids ratios. Pressure did not greatly influence the size of the bubbles generated in the process, or the removal efficiencies. High air-to-solids ratios were necessary to obtain maximum removal efficiencies and to prevent appreciable settling of the suspended solids.

Liquid/suspended solid phase partitioning of polycyclic aromatic hydrocarbons in coal coking wastewaters

Wastewater samples were collected from five streams among two coke plants and characterized by high pressure liquid chromatography and gas chromatographic mass spectrometry. Wastewater streams included the ammonia still influent, ammonia still effluent and biological oxidation effluent. Samples collected from these streams were separated into liquid and suspended solid phases and each phase was analyzed for eleven polycyclic aromatic hydrocarbons (PAH). Total wastewater concentrations for these compounds ranged from about 2000 μg l −1 in the ammonia still influent to 5–120 μg l −1 in the biological oxidation effluent. Wastewater PAH were partitioned between liquid and suspended solid phases, and in most samples suspended solid phase PAH accounted for approx. 80% or more of total wastewater PAH. Partitioning in the biological oxidation effluent stream was correlated with aqueous solubility and n-octanol/water partition coefficients. Wastewater treatment consisting of sedimentation, ammonia stripping, and biological oxidation generally reduced liquid phase PAH concentrations to the range of 1 μg l −1 or less. Effective removal of wastewater suspended solids will reduce total effluent PAH concentrations, hence there is need to address issues regarding removal of residual wastewater suspended material including characterization of the distribution of PAH with respect to suspended particle size.