Modified Coal Fly Ash Research Articles

Marine oil spill remediation by Candelilla wax modified coal fly ash cenospheres

Biodegradable candelilla wax (CW) was creatively used for hydrophobic modification of coal fly ash cenospheres (FACs), a waste product from thermal power plants, and a new spherical hollow particulate adsorbent with fast oil adsorption rate and easy agglomeration was prepared. CW was confirmed to physically coat FACs and the optimum mass of wax added to 3 g of FACs was 0.05 g. From a series of batch scale experiments, CW-FACs were found to adsorb oil, reaching adsorption efficiency of 80.6% within 10 s, and aggregate into floating clumps which were easily removed from the water's surface. The oil adsorption efficiency was highly dependent on hydrophobicity of the used adsorbent, the adsorption of Venezuela oil onto CW-FACs was found to be a homogenous monolayer, and the capacity and intensity of the adsorption decreased as temperature increased from 10 to 40 °C. The Langmuir isotherm model was the best fit, with the maximum adsorption capacity achieved at 649.38 mg/g. CW-FACs were also found to be highly stable in concentrated acid, alkaline and salt solutions, as well as for spills of different oil products. Furthermore, the retention rate of the oil adsorption capacity of the CW-FACs after 6 cycles of adsorption-extraction was as high as 93.2%. Therefore, CW-FACs can be widely used, easily recycled, and reused for marine oil spill remediation, which is also a good alternative disposal solution for FACs.

The synergistic adsorption-catalysis research of highly efficient interlayer constructed from coal fly ash for superior lithium-sulfur batteries

The notorious shuttle effect severely limits the practical application of Lithium-Sulfur Batteries (LSBs). In line with the concept of “green chemistry”, industrial solid waste is reasonably applied to the design of battery’s interlayer. The modified coal fly ash (MCFA) can effectively accelerate the redox kinetics of the electrode and optimize the nucleation and decomposition of Li2S. The synergistic adsorption and catalytic action from rich pore structure and polar metal oxides can effectively capture and fix free polysulfide (LiPSs), which realizes the inhibition of shuttle effect. The LSBs with MCFA interlayer exhibit good cycle stability (decay-rate: 0.05% per cycle) and rate capability (703 mAh g−1 at 3C). Even under extreme conditions of poor electrolytes (E/S = 7.8 μL /mg), Cell-MCFA/PE with a high S loading (7.5 mg cm−2) still performs well (732 mAh g−1 after 100 cycles). This work provides an economical and environment-friendly strategy for the design of interlayer, which is conducive to the commercialization process of LSBs.

Highly efficient separation of uranium from wastewater by in situ synthesized hydroxyapatite modified coal fly ash composite aerogel

In this work, hydroxyapatite (HAP) was in situ synthesized on coal fly ash (CFA) to prepare hydroxyapatite modified coal fly ash composite aerogel (HCFAA). The maximum removal efficiency and capability of uranium(VI) on HCFAA were 97.6 % and 205.7 mg g−1, respectively, which was much higher than those of CFA (83.6 % and 59.1 mg g−1) (pH = 3.0, m/V = 1.0 g/L and T = 298 K). The desorption efficiency of uranium(VI) by HCFAA was even more than 80 % after five cycles, demonstrating that the introduction of HAP had improved uranium(VI) removal performances. Pseudo-second-order and Langmuir models were fitted better with the experimental data, indicating the uranium(VI) removal process was a homogeneous monolayer chemisorption. Meanwhile, the uranium(VI) removal efficiency for HCFAA in actual wastewater was higher to 80.6 % and uranium(VI) could even be completely separated from actual wastewater by HCFAA during dynamic adsorption (m = 50 mg, V = 400 mL, C0 = 10 mg/L), further illustrating that the introduction of HAP was an available method to modify CFA. Characterizations results demonstrated that uranium(VI) was successfully immobilized on HCFAA through ion exchange, dissolution-precipitation and surface complexation. In conclusion, HCFAA was a prospective adsorbent for uranium(VI) separation in practical application.

Modified coal fly ash for textile dye removal from industrial wastewater

Complex dyes have an adverse impact on the environment since they have a high aqueous solubility and are very challenging to be removed using conventional approaches. A series of batch tests were performed to determine the optimum parameters for the direct blue 78 dye adsorption process as a function of chemically treated coal fly ash (TCFA) Effect of fly ash dose, contact time and dye initial concentration were studied using an industrial wastewater. A pilot plant, consisting of three stages; mixing, sedimentation and filtration was designed and implemented to investigate the ability of TCFA to remove COD, BOD5, TDS and TSS from textile wastewater under optimal conditions. A series of fly ash physico-chemical analysis including particles size analysis, zeta potential, XRD, EDX, BET, SEM and FTIR were investigated. The results showed that the particles size and zeta potential for raw coal fly ash were 1.2 µm and −20.70 mv. Chemical treatment process using hydrochloric acid resulted reducing the particles size of fly ash from 1.2 µm to 0.95 µm. Zeta potential value increased to + 7.20 mv. Batch adsorption process showed that the removal efficiency decreased as the primary dye concentration increased. It increased when fly ash loading and contact time increased. Dyes removal was achieved up to 99.7% using TCFA loading 3gL−1 for initial dye concentration10 mgL−1. Studies on equilibrium revealed that the equilibrium data was closely fitted to the Freundlich and Langmuir isotherm models. Kinetic study of adsorption process was studied in detial. Based on high correlation coefficient (R2 = 0.999), the results were followed pseudo second-order model.

Utilization of chemically modified coal fly ash as cost-effective adsorbent for removal of hazardous organic wastes

Disposal of dyes wastewater into aquatic streams is considered as a major challenge due to its effect on water ecosystem. Direct dyes have a complex aromatic structure. Therefore, it is difficult to separate them from industrial wastewater. Conversely, fly ash is a main by-product pollutant generated from coal burning to fulfill energy requirements. In this study, thermochemical treatment process was applied to coal fly ash (CFA) in order to increase its surface area, improve its pore’s structure and enhancing its adsorption capacity for direct blue 78 dye (DB78) removal. The treated coal fly ash (TCFA) was characterized by physicochemical analyses such as XRD, XRF, TGA, SEM, FTIR, surface area (SBET) and particles size analysis. Batch experiments were conducted to analyze the adsorption behavior for TCFA and to examine the DB78 dye removal efficiency. The physicochemical analysis results indicated that a higher increase in CFA surface area from 9.6 to 60.4 m2g−1 was obtained due to the modification process. The maximum removal efficiency using TCFA was 99.7% for initial dye concentration 10 mg/L and TCFA dose 2 g/L. The adsorption isotherm was studied by Langmuir and Freundlich model using different dye concentrations. The results showed that equilibrium data followed closely Langmuir isotherm model (R2 = 0.99) indicating monolayer and homogeneous adsorption process.

The selective adsorption of rare earth elements by modified coal fly ash based SBA-15

The modification of fly ash based SBA-15 enables the selective adsorption of REE(III) with a high capacity. • The species distribution of rare earth elements ions was simulated. • DTPADA-SBA-15 owned high adsorption efficiency and selectivity for REE (III). • DTPADA-SBA-15 owned preferable reusability in acidic solution. Rare earth elements (REE) are strategic resources and the recycling of REE in alternative resources is urgent and gets increasingly attention. However, the separation of REE in these alternative resources is still a challenge due to the low concentration of REE and multi coexisted ions in acidic system. In this study, the species distribution of REE within the pH 0–8.0 was calculated. The SBA-15 originated from coal fly ash was modified by two steps with (3-aminopropyl) triethoxysilane (APTES) and diethylenetriaminepentaacetic dianhydride (DTPADA) to obtain DTPADA-SBA-15 adsorbent, which was applied to the selective adsorption of REE. The results showed that DTPADA-SBA-15 possessed excellent adsorption performance on the selective adsorption of REE, including Eu, Gd, Tb, Nd and Sm, in acidic solution (pH 2) with multi competing ions. The FT-IR and Zeta potential characterization verified that the chemical adsorption through the coordination of O in DTPADA-SBA-15 with REE was dominant at lower pH value. The study of adsorption kinetics indicated that the adsorption of rare earth metal ions followed pseudo-second-order kinetic, of which the adsorption process followed the Langmuir isotherm model.

Valorization of alkaline hydroxide modified coal fly ash to efficient adsorbents for enhanced carbon capture

High carbon content coal fly ash was used in this study to synthesize an adsorbent using two step fusion hydrothermal method. Both KOH and NaOH were used in the fusion to observe deviations from the usual NaOH method. They were compared in terms of their physico-chemical attributes. The SEM micrographs showed that coal fly ash lost its geoid structures after fusion with the alkalis. XRD diffractograms showed that both K/Na/CFA-Heavy adsorbent and K/Na/CFA-Light adsorbent were highly amorphous. The K/Na/CFA-Light adsorbent had inferior morphology but better BET than K/Na/CFA-Heavy adsorbent. Even in terms of CO2 uptake capacity, at room temperature K/Na/CFA-Light adsorbent (1.48 mmol/g) outperformed K/Na/CFA-Heavy adsorbent (1.13 mmol/g). A maximum value CO2 uptake value of 1.48 mmol/g was observed for K/Na/CFA-Light adsorbent at 298 K. Kinetic studies displayed that the adsorption process was best explained by the Avrami model with an R2 value of 0.99. Cyclic stability studies were performed at 298 K and they showed that that K/Na/CFA-Light adsorbent showed a cyclic retention capacity of 80% at the end of five cycles.

Modified coal fly ash as a low-cost, efficient, green, and stable adsorbent for heavy metal removal from aqueous solution

Modified coal fly ash as a low-cost, efficient, green, and stable adsorbent for heavy metal removal from aqueous solution

Assessment of Alkali Modified Coal Fly Ash As a Potential Pit Latrine Additive for Elimination of Pathogens Using Synthetic Faeces As Proxy

In this study, alkali modified coal fly ash (MFA) and unmodified coal fly ash (unMFA) were applied, as pit latrine additives to eliminate faecal coliforms from synthetic faeces (SF), which were used as a proxy for real pit latrine waste. The X-ray diffractogram spectrum showed that mullite and quartz were converted into hydroxysilicate. Two separate studies were run over a period of seven weeks. The first study had the treatment combinations of SF: MFA, SF: unMFA, SF: MFA: synthetic greywater (SGW), SF: unMFA: SGW, SF: MFA: synthetic urine (SU), SF: unMFA: SU and SF (as a control) while the second study consisted of the combinations of SF: MFA, SF: unMFA, SF: MFA: lime (6g), SF: unMFA: lime (12g), SF: MFA: lime (24g), SF: unMFA: lime (50g) respectively. The pH in both studies ranged between 7.07 and 12.38. The average initial concentrations of faecal coliforms from each of the experimental treatments ranged from 9.96 x 106 to 1.06 x107 ± 2 x106 cfu/g of dry weight on the first day of the experiment. However, they were removed completely after 7 days with no regrowth for a period of 7 weeks indicating removal of faecal coliforms to level below the detection limits of the enumeration technique used. On the first study on the fourth week, faecal coliforms reappeared in the pit latrine treatment SF: MFA: SU (5.60 x 105 ± 8.66 x 105 cfu/g dry weight) followed by SF: MFA (1.78 x 105 ± 2.89 x 105 cfu/g dry weight) but thereafter could not be detected (detection limit was 545 cfu/ g dry weight of SF) for the remainder of the study. The concentration of chemical oxygen demand (COD), ammonium, phosphate ranged between 6.35 x102 ± 1.26x102 – 22.11 x102, 0.116±0.091 – 21.38 x102 ± 1.77x102 and 1.35x102 ±0.348 – 31.18x102 ±0.348 mg/g of dry weight respectively while nitrate concentration was zero. In conclusion, both studies showed that MFA and unMFA can be used as pit latrine additives for the removal of pathogenic microorganisms, however, the contents of the pit latrine might have an influence on how fast and effective the additive might be as shown in the first study where SU or SGW were introduced.

Experimental Research on the Gaseous Pbcl2 Adsorption by Thermal Alkali Modified Coal Fly Ash

Experimental Research on the Gaseous Pbcl2 Adsorption by Thermal Alkali Modified Coal Fly Ash

Adsorptive removal of fluoride from water by chemically modified coal fly ash: Synthesis, characterization, kinetics, and mechanisms

Raw fly ash (RFA) was modified using NaOH and FeCl3 (NaOH/Fe-MFA) to enhance the adsorptive properties for removal of fluoride from water. SEM-EDX, XRD and FTIR, point for zero charge (PZC), specific surface area, and particle size were considered to contrast adsorbent properties of RFA and NaOH/Fe-MFA. The impact of operating variables such that initial solution pH, contact time, adsorbent dosage over fluoride adsorption were evaluated using synthetic water samples. Isotherm and kinetics studies were performed for NaOH/Fe-MFA. Adsorption experiments showed a higher adsorption capacity for NaOH/Fe-MFA over RFA. After 2 h reaction, maximum fluoride removal of 92% was observed with 2 g L−1 of NaOH/Fe-MFA at pH 2. At pH 7, under similar conditions, 34% of removal was observed. Fluoride adsorption from NaOH/Fe-MFA was followed Langmuir isotherm, and monolayer fluoride adsorption on homogeneous NaOH/Fe-MFA was confirmed with a considerably high capacity of 18.6 mg g−1. Chemisorption adsorption was revealed from well-fitted kinetics data with pseudo-second-order model. Dominant mechanism for fluoride adsorption from NaOH/Fe-MFA was identified as iron exchange with surface OH−, which bonds to Fe3+ ions.

Modification of coal fly ash and its use as low-cost adsorbent for the removal of directive, acid and reactive dyes

Directive, acid and reactive dyes are the carcinogenic dyes which have complex structures and difficult to remove from the industrial wastewater. In this study, coal fly ash (CFA) was modified with HCl and NaOH solution and used for the removal of direct fast scarlet 4BS, direct sky blue 5B, acid navy blue R, and reactive turquoise blue KN-G dyes. Laboratory experiments were carried out to analyze the performance of modified coal fly ash (MCFA) to check the removal efficiency and adsorption capacity of dyes. The maximum removal efficiency of direct fast scarlet 4BS and direct sky blue 5B were recorded 96.03% and 93.820%, respectively using 0.05 g adsorbent dosage at 100 mg/L initial concentration. The results of MCFA were compared with carbon black, chitosan, starch, zeolite and unmodified coal fly ash (UMCFA) at lower dosage 0.05 g and higher dosage 0.4 g. Adsorption isotherm were analyzed by Langmuir and Freundlich model by different dyes concentrations, the result stated that Freundlich and Langmuir model (±0.9918, ±0.9974) was fitted by chemisorption and physisorption methods for all four dyes. Adsorption kinetic were also determined by Pseudo-first-order and Pseudo-second-order at different contact times with dye molecules and adsorbent active sites, and the results showed that the adsorption behaviors of all four dyes were described better by pseudo-second-order kinetics than pseudo-first-order kinetics. Recommended dosage of modified fly ash is between 10 ‱ to 20 ‱ for simulated textile industrial waste water and regeneration temperature is 300 ℃.

Effect and mechanisms of synthesis conditions on the cadmium adsorption capacity of modified fly ash

In this study, modified coal fly ash (NMFA) was prepared by sodium hydroxide (NaOH) with low-temperature hydrothermal method. The differences of the ash to alkali mass ratio (5:3, 5:4, 5:5, 5:6), calcination temperature (100 ℃, 200 ℃, 300 ℃), and calcination time (1 h, 3 h, 5 h) were investigated. The adsorption experiments obtained the optimal result with the ash to base ratio of 5:5, calcination temperature of 200 ℃, and calcination time of 3 h, adsorbing 90.27 mg/g of Cd2+. The characterization results (SEM-EDS, FTIR, XRD, and XPS) also confirmed the effective adsorption of Cd2+ by NMFA. The functional groups of Si-O, Al-O, and Fe-O played an important role in Cd2+ removal. Meanwhile, the influences of dosage, different pH, and co-existing cations were also investigated. Quasi-secondary adsorption kinetics and Langmuir isotherm model were also referred to the Cd2+ adsorption by NMFA. Therefore, the good adsorption of NMFA-3 on Cd2+ provided new ideas for the safe utilization of fly ash and heavy metal purification in wastewater.

Stabilization of lead in waste water and farmland soil using modified coal fly ash

As a by-product of coal-fired power plants, fly ash has attracted widespread attention because of its heavy metal adsorption potential. In this study, two fly ashes from different power plants were re-used through modification to adsorb Pb(Ⅱ) from aqueous solution and field soil. The physicochemical properties of adsorbents were characterized by X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), the X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as the X-ray photoelectron spectroscopy (XPS). In addition, batch sorption experiments and field study were conducted to investigate their adsorption capacity on Pb(Ⅱ). The results demonstrated that, the surface area of modified fly ash-2 (MFA-2) has increased 25 times. The kinetic study illustrated that the adsorption process on both modified fly ash-1 (MFA-1) and MFA-2 were more suitable for pseudo-second-order model. Nevertheless, MFA-2 took less time to reach adsorption equilibrium. Compared with the raw fly ashes, the prepared MFAs had stronger affinities to Pb(II). When used as adsorbents, more than 146 and 165 mg of Pb(II) could be adsorptively stabilized by per gram of MFA-1 and MFA-2 at 318 K from waste water, respectively; when employed as amendments, the addition of MFA-1 and MFA-2 into soil could reduce Pb accumulation in rice, with the total Pb content in rice grains is lower than the level of natural standard. The investigation declared that the MFAs were promising materials which had great potentials on adsorptive stabilization of Pb(II) from waste water and contaminated soil, which also realizes the recycling of resources and cleaner production.

Removal of Cadmium from Contaminated Groundwater Using a Novel Silicon/Aluminum Nanomaterial: An Experimental Study.

Cadmium (Cd) is a harmful element to human health and biodiversity. The removal of Cd from groundwater is of great significance to maintain the environmental sustainability and biodiversity. In this work, a novel low-temperature roasting associated with alkali was applied to synthesize an eco-friendly adsorbent using coal fly ash. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray fluorescence, and X-ray photoelectron spectroscopy were applied to analyze the physical and chemical characteristics of the adsorbent. The experiments show that a significant improvement in specific surface area and activity of adsorbent was observed in this study. The functional groups of Na-O and Fe-O were verified to be beneficial in the removal of Cd2+. The material capacity to adsorb Cd2+ was considerably improved, and themaximum uptake capacity was 61.8mgg-1 for Cd2+ at 25°C. Furthermore, pH and ionic strength play critical roles in the adsorption process. The Langmuir and pseudo-second-order models can appropriately describe the adsorption behavior, and the enhanced adsorption ability of Cd2+ by modified coal fly ash was attributed to ion-exchange, co-precipitation, and complexation. Higher sorption efficiency was maintained after two regeneration cycles. These results offer valuable insights to develop high-performance adsorbent for Cd2+ removal.

Utilization of Modified Coal Fly Ash (CFA) as a Catalyst for Production of Biodiesel from Coconut Oil: Part 1 - Characteristics of the Catalyst

The current research studied about the utilization of modified coal fly ash (CFA) as catalyst for biodiesel production from coconut oil. Coal Fly ash (CFA) is a solid waste that is abundantly available in the coal-based power plant. Coal Fly Ash is a type of material that has high content of oxide minerals, e.g. silicates and silicate alumina. With proper physical/chemical treatment, the coal fly ash can be converted into a heterogeneous catalyst. In this work, the coal fly ash was modified with HCl and Ca(NO3)2·4H2O and used as catalyst for biodiesel production from coconut oil. This paper will focus only on the characteristics of the prepared modified CFA-based catalyst. The modified CFA-based catalyst was characterized for its crystallinity using X-Ray Diffraction (XRD), determined its surface area and pore size distribution using Surface Area Analyzer, and its functional groups by Fourier Transform – Infra Red (FT-IR). The specific surface area of the catalyst (modified CFA) decreased from 28.08 m2/g to 17.54 m2/g after impregnation process of calcium oxide in the raw coal fly ash. This decrease was also accompanied by a decrease in the average pore network from 32.59 Å to 20.31 Å. Additionally, based on the XRD pattern shown, the raw CFA is composed of mostly quartz (SiO2) and mullite (3Al2O3.2SiO2) minerals, and a small portion of hematite.

Optimization of preparation technology for modified coal fly ash and its adsorption properties for Cd2+

This work focused on preparation a novel adsorbent from coal fly ash (CFA) and solid alkali (NaOH) by low temperature roasting method. The modification parameters (mass ratio, calcination time and temperature) were specifically studied and optimized. The adsorption experiment results indicated that, the adsorption amounts of Cd2+ were enhanced with the decreasing mass ratio of CFA and NaOH, and the adsorption amounts of Cd2+ were 32.44, 31.66, 38.5 and 79.85 mg/g at the mass ratio (CFA/NaOH) of 5:5, 5:6, 5:7 and 5:8, respectively. The higher modification temperature was not conducive to the removal of Cd2+, as the adsorption capacities of Cd2+ calculated were 62.42, 69.53 and 41.73 mg/g at the reaction temperature of 250, 300 and 400 ℃. Interestingly, the modification time slightly effects on the adsorption ability of materials. According to the results, the optimum modification condition for preparing adsorbents were CFA/NaOH mass ratio of 5:8 and calcined at 300 ℃ for 3 h. Moreover, the influence of pH, ionic strength and Glycine concentration on Cd2+ uptake were also investigated. The kinetic, adsorption isotherm and thermodynamics models were applied to investigate the adsorption mechanism, which indicated that the adsorption process was better fitted by Langmuir and pseudo-second-order models.

Effect of surface-modified fly ash on compressive strength of cement mortar

This paper presents the experimental results on the impact of modified coal fly ash on mechanical performance of cement materials. Fly ash used in the experiments was received from Burshtyn thermal power plant (Ukraine). The surface modification was carried out by the acidic treatment in order to increase its pozzolanic activity. The impact of raw fly ash and surface-modified fly ash on the cement mortar strength have been compared. It was found in the experiments that the replacement of cement by 5% (wt) of modified fly ash increase the compressive strength value from 61.3 MPa to 63.2 MPa compared to unmodified fly ash at age 28 days. The mineral phase formation, structure and chemical compositions of the modified fly ash/cement composites were analyzed by XRD, SEM and EDS. This research is of great importance and opens a new way for the future investigation and utilization of coal fly ash.

Modified coal fly ash waste as an efficient heterogeneous catalyst for dehydration of xylose to furfural in biphasic medium

For the first time, application of acid-treated coal fly ash as a catalyst for selective dehydration of d-xylose to furfural was investigated in this work. Coal fly ash had been treated with sulphuric acid to promote de-alumination and consequently enhance the silanol concentration in the modified catalyst. This Brønsted acidic catalyst had been effective to convert 85% d-xylose to yield 62% furfural at 170 °C. On addition of 35 ppt of NaCl to the system furfural yield was improved to 68%. This promising result in equivalent salinity of sea water might open up possibilities to investigate inexpensive sea water as a replacement of distilled water to improve the product yield. The catalyst was stable enough to sustain minimum of 6 cycles of run. Apart from the abundant availability and cheap price of fly ash, utilizing it for heterogeneous catalysis drives to mitigate disposal problems of fly ash to partial extent. The dual advantages make the system eco-friendly.

Preparation of nano-Fe0 modified coal fly-ash composite and its application for U(VI) sequestration

The nanoscale zero valent iron (NZVI) modified coal fly ash (CFA) magnetic composites (NZVI/CFA) were synthesized from the waste CFA and applied for the high-efficiency sequestration of U(VI) ions from water solution. The sequestration capacity of U(VI) ions on NZVI/CFA (0.62 mmol·g−1) was larger than that on bare CFA (0.25 mmol·g−1) or NZVI (0.38 mmol·g−1). The sequestration of U(VI) on NZVI and NZVI/CFA was primary controlled by outer-sphere surface complexation at low pH, and by inner-sphere surface complexation at high pH. According to the thermodynamic data and the adsorption isotherms' analysis, the U(VI) sorption process to the NZVI/CFA was spontaneous and endothermic. The main reaction mechanism was that, most of the soluble U(VI) ions were firstly adsorbed to NZVI/CFA and then the surface adsorbed U(VI) was partly reduced to U(VI) on the porous NZVI/CFA composites, and this synergistically affected U(VI) removal from solution to NZVI/CFA. The results of DFT calculation indicated that the NZVI/CFA had a strong sequestration capacity towards U(VI) and U(IV) ions, and the binding energy of U(IV) species was larger than that of U(VI) species, which evidenced the higher sorption of U(IV) than U(VI) on NZVI/CFA. The results showed that NZVI/CFA was an appropriate material for U(VI) sequestration from large volumes of actual effluent in wastewater cleanup.