Strength Wastewater Research Articles

Synchronized urban wastewater treatment and biomass production using duckweed Lemna gibba L.

This work compiles results of utilizing duckweed Lemna gibba L. in sewage wastewater treatment and converting wastewater nutrients into protein and carbohydrate rich weed biomass. A total of four different strengths of wastewater (100, 75, 50 and 25%) were used to build experimental setups and changes in chemical properties of wastewater were measured at the end. L. gibba L. caused a decrease in pH (9–13%), EC (13–26%), NO3−N (42–64%), SO4−2 (35–82%), total phosphorus (37–54%), totNa (44–75%), totK (45–76%) and totCa (51–72%). The biomass yield in L. gibba L. ranged between 132.62 and 200.95g/m2day (fresh weight) or 23.87 and 36.17g/m2day (dry weight); about 24.6–36.17% higher than initial level in all experimental setups. The weed biomass was 24.6–52.8% higher than initial level in all set-ups. The yield rate of protein and carbohydrate ranged 1.19–1.95g/m2day (dry weight) and 22.72–35.58g/m2day (dry weight), respectively in duckweed systems. The high carbohydrate and protein yield in L. gibba advocates the utility of the weed in animal feed and bioethanol production. Results suggested that L. gibba can be utilized effectively for designing of a synchronized wastewater treatment and biomass harvesting system.

Polishing of synthetic electroplating wastewater in microcosm upflow constructed wetlands: Effect of operating conditions

This paper addresses the issue of polishing electroplating wastewater in subsurface vertical flow constructed wetland. Electroplating wastewater treatment or polishing in constructed wetlands (CWs) was studied to a very limited degree. Four types of microcosm upflow constructed wetlands were selected for the experiment based on type of bed media and the presence or absence of vegetation (Phragmites australis). The main objective of the system design was to promote metals removal by precipitation as sulfides mediated by sulfate reducing bacteria. The experimental system consisted of eight PVC columns (diameter 20cm) filled up to. 63.5cm with either gravel or gravel–peat mixture and was operated for one year, polishing synthetic electroplating wastewater. The wastewater used in this study contained metals (Cu, Ni, Pb and Zn), cyanides and sulfates, which typically occur in electroplating wastewater. During the experiment the effect of the following factors was studied: presence of vegetation, hydraulic loading, wastewater strength, type of bed media, and addition of lactates as external carbon source for the columns with gravel. The results showed that the upflow columns can efficiently remove metals (with the exception of Pb) and cyanides. It was observed that the removal efficiency of Cu, Ni and Zn increases with increasing influent concentration of metals and increasing hydraulic loading rate. The role of plants and bed media was minor. The addition of lactates to the feed of the columns with gravel was found to improve the reduction of metals concentration in the passing wastewater.

The comparison of different mathematical methods to determine the BOD parameters, a new developed method and impacts of these parameters variations on the design of WWTPs

One of the most common tests for the determination of strength and organic content of wastewater is the biochemical oxygen demand (BOD). This test is widely applied to define organic water pollution and to control the performance of wastewater treatment plants. Generally, BOD is standardized by the measurement of oxygen consumption in 5days (BOD5). But, determination of the ultimate biochemical oxygen demand (BODu), which is taken 28days and the reaction rate constant (k) are necessary to understand the organic strength of the wastewater. In this study, the different mathematical methods in order to determine the BOD parameters (BODu, k) and two different BOD test method (respirometer and dilution method) are investigated comparatively. Also, a new method based on cubic spline method to estimate ultimate BOD values is developed. Moreover, the impacts of BOD parameters on the design of an activated sludge and aerated lagoon systems are analyzed by using a written user-friend program, which is developed for designing WWTPs by the mean of C++ programming language.Analytical results show that there is a satisfactory linear relationship between respirometric and dilution BOD values. Also, the mathematical methods, including new developed method generally provide consistent results with high correlation coefficients. On the other hand, it is found that LOG differences method for respirometric test and the new developed method for dilution test do not give good correlation coefficients. Moreover, activated sludge and aerated lagoons systems’ sizes show significant changing depending on the variations of the BOD parameters. Consequently, BOD parameters show significant changes depending on the different test and mathematical methods. Therefore, the changing of these parameters impact a lot of situation such as ultimate BOD estimation, the wastewater treatment plants design, the dimensions of the plants and cost of the plants.

Atrazine removal from aqueous solutions using submerged biological aerated filter

Atrazine is widely used in the agriculture as an herbicide. Due to its high mobility, Atrazine leaks into the groundwaters, surface waters, and drinking water wells. Many physical and chemical methods have been suggested for removing Atrazine from aquatic environments. However, these methods are very costly, have many performance problems, produce a lot of toxic intermediates which are very harmful and dangerous, and cannot completely mineralize Atrazine. In this study, biodegradation of Atrazine by microbial consortium was evaluated in the aquatic environment. In order to assess the Atrazine removal from the aquatic environment, submerged biological aerated filter (SBAF) was fed with synthetic wastewater based on sucrose and Atrazine at different hydraulic retention times (HRTs). The maximum efficiencies for Atrazine and Soluble Chemical Oxygen Demand (SCOD) removal were 97.9% and 98.9%, respectively. The study findings showed that Stover-Kincannon model had very good fitness (R2 > 99%) in loading Atrazine in the biofilter and by increasing the initial concentration of Atrazine, the removal efficiency increased. Aerobic mixed biofilm culture was observed to be suitable for the treatment of Atrazine from aquatic environment. There was no significant inhibition effect on mixed aerobic microbial consortia. Atrazine degradation depended on the strength of wastewater and the amount of Atrazine in the influent.

Nitrogen removal from temperate anaerobic–aerobic two‐stage biological systems: impact of reactor type and wastewater strength

AbstractBACKGROUNDThere is a need to examine the impact of anaerobic reactor type and wastewater strength on anaerobic–aerobic two‐stage biological systems for temperate wastewater treatment An expanded granular sludge blanket reactor and an anaerobic membrane bioreactor for crude wastewater treatment with downstream aerobic biological treatment were studied together with increasing the organic concentration by fortifying the crude wastewater with primary sludge.RESULTSA chemical oxygen demand and ammonia compliant effluent was produced from the anaerobic–aerobic two‐stage process. Due to the enhanced organics removal achieved by the membrane, a lower denitrification rate, kd, was recorded for the anaerobic membrane bioreactor effluent treatment. However, the residual organic carbon in the anaerobic effluents from both the expanded granular sludge blanket reactor and the anaerobic membrane bioreactor treating crude wastewater was not of sufficient quality to support denitrification. Complete nitrification was achieved during downstream treatment of the fortified effluent. In addition, fortification increased kd to values analogous to exogenous carbon substrates.CONCLUSIONSIt is postulated that fortification currently presents the most sustainable strategy for anaerobic–aerobic two‐stage biological systems due to a combination of enhanced methane production and denitrification. © 2013 Society of Chemical Industry

Parameters affecting the occurrence and removal of polybrominated diphenyl ethers in twenty Canadian wastewater treatment plants

This study determined PBDE levels in influent, primary effluent, and final effluent collected from diverse treatment processes including four aerated lagoons, two facultative lagoons, four primary treatments, eight secondary biological treatments and two advanced treatments. Parameters examined for correlation included seasonal temperature, community sizes, industrial inputs, and operational conditions. PBDE levels in influent were 21–1000 ng/L (median 190 ng/L). Higher concentrations in influent samples were found during summer, and in WWTPs which treated leachate and higher proportions of industrial wastewater vs. residential wastewater. Final effluent levels ranged between 3 and 270 ng/L (median 12 ng/L). Among all congeners, the sum of BDE-209, -47 and -99 accounted for 79 and 71% of total PBDEs in influent and final effluent, respectively, with BDE-209 having the highest proportion. Median removal efficiencies for all process types exceeded 90% except primary treatment at 70%. PBDE levels and removals were correlated to the levels and removals of conventional parameters that represent wastewater strength, such as chemical oxygen demand and total suspended solids. The role of the primary clarifier was significant (∼82% removal) and removal was associated with hydraulic retention time (HRT) and surface loading rate. Best removal of PBDEs was achieved at greater than 2000 mg/L mixed liquor suspended solids (MLSS), longer than 10 h of HRT, and 9 days of solids retention time.

Electricity generation from young landfill leachate in a microbial fuel cell with a new electrode material

This study aims at evaluating the performance of a two-chambered continuously fed microbial fuel cell with new Ti-TiO₂ electrodes for bioelectricity generation from young landfill leachate at varying strength of wastewater (1-50 COD g/L) and hydraulic retention time (HRT, 0.25-2 days). The COD removal efficiency in the MFC increased with time and reached 45 % at full-strength leachate (50 g/L COD) feeding. The current generation increased with increasing leachate strength and decreasing HRT up to organic loading rate of 100 g COD/L/day. The maximum current density throughout the study was 11 A/m² at HRT of 0.5 day and organic loading rate of 67 g COD/L/day. Coulombic efficiency (CE) decreased from 57 % at feed COD concentration of 1 g/L to less than 1 % when feed COD concentration was 50 g/L. Increase in OLR resulted in increase in power output but decrease in CE.

Autotrophic nitrogen removal from low strength waste water at low temperature

Direct anaerobic treatment of municipal waste waters allows for energy recovery in the form of biogas. A further decrease in the energy requirement for waste water treatment can be achieved by removing the ammonium in the anaerobic effluent with an autotrophic process, such as anammox. Until now, anammox has mainly been used for treating warm (>30 °C) and concentrated (>500 mg N/L) waste streams. Application in the water line of municipal waste water treatment poses the challenges of a lower nitrogen concentration (<100 mg N/L) and a lower temperature (≤20 °C). Good biomass retention and a short HRT are required to achieve a sufficiently high nitrogen loading rate. For this purpose a 4.5 L gaslift reactor was inoculated with a small amount of anammox granules and operated for 253 days at 20 °C. The synthetic influent contained (69 ± 5) mg (NH4+ + NO2−)/L and 20 vol.% of anaerobically stabilised effluent. Results showed a clear increase in nitrogen loading rate (NLR) up to 0.31 g (NH4 + NO2)-N/(L × d) at a hydraulic retention time (HRT) of 5.3 h. A low effluent concentration of 0.03–0.17 mg (NH4++NO2−)-N/L could be achieved. Anammox biomass was retained as granules and as a biofilm on the reactor walls, which contributed 54 and 46%, respectively, towards total activity. The biomass was further characterised by an estimated net growth rate of 0.040 d−1 and an apparent activation energy of 72 kJ/mol. The results presented in this paper showed that anammox bacteria can be applied for autotrophic nitrogen removal from the water line at a municipal waste water treatment plant. Combining direct anaerobic treatment with autotrophic nitrogen removal opens opportunities for energy-efficient treatment of municipal waste waters.

Performance Evaluation of Wastewater Treated Plant for Ninava Drug Factory

In this study the characteristics of raw and treated wastewater from Ninava drug factory were evaluated. The results revealed that the strength of raw wastewater can be classified as medium concentrated wastewater with respect to its BOD5 since the average value is 231.7 mg/l. In addition a strong correlations were found between many characteristics of raw waste. The characteristics of produced effluent from waste water treatment plant of the factory were within the Iraqi specification for the disposed wastewater constraints in 1997, where the average is 7.8 for pH, 40mg/l for SS, 2.8 mg/l for PO4-3, 45 mg/l for BOD5 and 104.3 mg/l for COD. The heavy metals concentrations for both raw and treated wastewater is to be less than those of the related literatures for Tigris river, municipal wastewater and water supply in Mosul city, the average heavy metal concentrations of raw and treated wastewater were 0.5 mg/l for Iron, 0.2 mg/l for zinc and 0.005 mg/l for copper, and there is no significant difference between raw and treated heavy metal concentrations.

Options to reduce greenhouse gas emissions during wastewater treatment for agricultural use

Treatment of primarily-domestic sewage wastewater involves on-site greenhouse gas (GHG) emissions due to energy inputs, organic matter degradation and biological nutrient removal (BNR). BNR causes both direct emissions and loss of fertilizer value, thus eliminating possible reduction of emissions caused by fertilizer manufacture. In this study, we estimated on-site GHG emissions under different treatment scenarios, and present options for emission reduction by changing treatment methods, avoiding BNR and by recovering energy from biogas. Given a typical Israeli wastewater strength (1050mg CODl−1), the direct on-site GHG emissions due to energy use were estimated at 1618 and 2102g CO2-eqm−3, respectively, at intermediate and tertiary treatment levels. A potential reduction of approximately 23–55% in GHG emissions could be achieved by fertilizer preservation and VS conversion to biogas. Wastewater fertilizers constituted a GHG abatement potential of 342g CO2-eqm−3. The residual component that remained in the wastewater effluent following intermediate (oxidation ponds) and enhanced (mechanical–biological) treatments was 304–254g CO2-eqm−3 and 65–34g CO2-eqm−3, respectively. Raw sludge constituted approximately 47% of the overall wastewater fertilizers load with an abatement potential of 150g CO2-eqm−3 (385kg CO2-eq dry tonne−1). Inasmuch as anaerobic digestion reduced it to 63g CO2-eqm−3 (261kg CO2-eq dry tonne−1), the GHG abatement gained through renewable biogas energy (approx. 428g CO2-eqm−3) favored digestion. However, sludge composting reduced the fertilizer value to 17g CO2-eqm−3 (121kg CO2-eq dry tonne−1) or less (if emissions, off-site inputs and actual phytoavailability were considered). Taking Israel as an example, fully exploiting the wastewater derived GHG abatement potential could reduce the State overall GHG emissions by almost 1%. This demonstrates the possibility of optional carbon credits which might be exploited in the construction of new wastewater treatment facilities, especially in developing countries.

Effects of Wastewater Strength and Salt Stress on Microalgal Biomass Production and Lipid Accumulation

Effects of Wastewater Strength and Salt Stress on Microalgal Biomass Production and Lipid Accumulation

Packed bed column studies for the removal of synthetic dyes from textile wastewater using immobilised dead C. tropicalis

An efficient dye biosorbent was developed for the treatment of textile wastewater by entrapping dead cells of C. tropicalis, within sodium alginate matrix. The biosorbent performance was evaluated in packed bed column with different pH (3 to 6), wastewater strength (25%, 50% 75%), bed height (5 cm–15 cm) and flow rate (0.5 mL min −1 to 1 mL min −1). pH 5, undiluted wastewater, bed height 15 cm and flow rate 0.5 mL min -1 were found to be optimum for dye biosorption. The linearized form of the modified Thomas model equation fitted well with the experimental data and described the dynamic adsorption of synthetic dyes from textile wastewater. The Bed depth service time model was used to express the effect of bed height on breakthrough curves. Dye laden immobilised dead C. tropicalis was regenerated using 0.01 mol L −1 NaOH at an elutant flow rate of 1 mL min −1. The reusability of the immobilised biomass was tested in consecutive adsorption–desorption cycles. The FT-IR spectral analysis showed the involvement of amine, hydroxyl, carbonyl, amide and phosphoryl groups in biosorption of dyes from wastewater. The analysis of treated samples showed almost zero colour and a significant decrease in Total Dissolved Solids (TDS).

Roadside rest area wastewater treatment system: Performance evaluation and improvement

The performance of a decentralised sewage treatment plant located at a rest area servicing a major freeway was investigated. Long term monitoring and rigorous analyses undertaken in this study revealed several unique and challenging issues associated with such scarcely studied systems. Data collected over a six month period showed that the raw wastewater strength was well above typical household wastewater characteristics, with the average BOD5, COD, TOC, TN and TP values of 880, 4900, 350, 238 and 8 mg/L, respectively. The system performance was considerably lower than that expected of a typical wastewater treatment unit. Several shortcomings in design (e.g., inefficient aeration device and return activated sludge system) and inconsistencies in maintenance practice were identified and some remedial measures were proposed and tested. Of particular interest were the increase of the dissolved oxygen (DO) concentration (from 0.5 to 4 mg/L) and the simultaneous significant improvement of COD and TOC removals in the aerobic reactor in response to the redesigning of the aeration system. The removal of nitrogen, however, remained quite low as expected.

Modelling the energy demands of aerobic and anaerobic membrane bioreactors for wastewater treatment

A modelling study has been developed in which the energy requirements of aerobic and anaerobic membrane bioreactors (MBRs) are assessed in order to compare these two wastewater treatment technologies. The model took into consideration the aeration required for biological oxidation in aerobic MBRs (AeMBRs), the energy recovery from methane production in anaerobic MBRs (AnMBRs) and the energy demands of operating submerged and sidestream membrane configurations. Aeration and membrane energy demands were estimated based on previously developed modelling studies populated with operational data from the literature. Given the difference in sludge production between aerobic and anaerobic systems, the model was benchmarked by assuming high sludge retention times or complete retention of solids in both AeMBRs and AnMBRs. Analysis of biogas production in AnMBRs revealed that the heat required to achieve mesophilic temperatures (35°C) in the reactor was only possible with influent wastewater strengths above 4–5 g COD L−1. The general trend of the submerged configuration, which is less energy intensive than the sidestream configuration in aerobic systems, was not observed in AnMBRs, mainly due to the wide variation in gas demand utilized in anaerobic systems. Compared to AeMBRs, for which the energy requirements were estimated to approach 2 kWh m−3 (influent up to 1 g COD L−1), the energy demands associated with fouling control in AnMBRs were lower (0.80 kWh m−3 for influent of 1.14 g COD L−1), although due to the low fluxes reported in the literature capital costs associated with membrane material would be three times higher than this.

Influence of water characteristics on partial nitrification in a sequencing batch reactor

Due to the potential benefits on energy/cost savings from partial nitrification, this studycarried a series of laboratory tests to study the combined influence from water temperature, organic carbon and dissolved oxygen (DO) on partial nitrification. The purpose of this study was to obtain a general direction to operate activated sludge systems for partial nitrification under changing environment conditions and wastewater strengths. The time profiles of the mixed liquor NO2-N and NO3-N during a 11 h aeration phase were monitored in a 6 L bench scale sequencing batch reactor (SBR) under varying water temperatures (20 to 30°C), organic carbon abundances(initial mixed liquor COD/N ratio ranged 2.8 to 14), and DO levels (0.4 to 4.0 mg L-1). Results showed that organic carbon abundance should be firstly lowered to below a certain threshold level (14 in this study) in order to allow nitrification to occur. Then, water temperature should be kept at relatively higher levels (at least 30°C) and DO should be controlled at relatively lower levels (depending on aeration duration). However, the adverse effect on partial nitrification from low water temperatures can be compensated by a low DO, while the favoring effect on partial nitrification from high water temperatures can be reversed by a high DO and/or excess aeration. Although it was not the focus of this study, simultaneous nitrification and denitrificaiton (SND) was also indicated viable when organic carbon abundance was kept at relatively higher levels but still below the inhibitory level for nitrification. Successive study is recommended to further quantify the interactions between these influential factors on partial nitrification and to improve and better understand the reliability and sensitivity of activated sludge systems in achieving partial nitrification under normally always changing reaction conditions. The overall conclusion is that partial nitrification is under normally always changing reaction conditions. Key words: Best management practice, bioreactor operation, nitrogen removal, wastewater, water temperatures, organic carbon abundances, dissolved oxygen (DO).

Process modification of a wire‐welding plant for efficient sulphate removal

AbstractSulphate removal by chemical precipitation from the wastewater of a wire‐welding facility was investigated. Sulphate was precipitated by using limestone and a small amount of lime. Firstly, the relationship between the ionic strength of wastewater and sulphate removal efficiency was established. A kinetic study of sulphate precipitation was also conducted. Finally, modification of plating process was proposed to achieve the highest sulphate removal. According to the suggested modification, the sulphate concentration of final discharge could be down to 425 mg/L. Hence, if wire‐welding facilities modify their systems so that the wastewater is treated at the highest level of sulphate contents, the removal efficiency will be the highest, i.e. lesser amounts of sulphate will be discharged into sewage systems.

Shock load response in an SBR-activated sludge process treating high load wastewater

In this study, the production of storage polymers is made when cheese production wastewater is treated. Cheese plants typically produce high-strength wastewaters on an intermittent basis and are particularly suitable for treatment in Sequencing Batch Reactor (SBR) systems. The SBRs were operated in triplicate under two filling scenarios: 'React Fill' (RF) with mixing/aeration; 'Static Fill' (SF) with no mixing/aeration. The results suggest that an 'SF' approach outperforms an 'RF' with respect to storage products production (50% more PHB, 15% more glycogen). Additionally, the famine phase duration will vary depending on wastewater strength, suggesting optimisation per waste stream.

Different depth intermittent sand filters for laboratory treatment of synthetic wastewater with concentrations close to measured septic tank effluent

The objective of this study was to apply hydraulic and chemical oxygen demand (COD) loading rates at the upper limits of the design criteria for buried sand filters to test the sand filter depth design criteria. Over a 274-day study duration, synthetic effluent with a strength of domestic wastewater was intermittently dosed onto two sand filters of 0.2 m diameter, with depths of 0.3 and 0.4 m. Hydraulic and organic carbon loading rates of 105 L m−2 d−1 and 40 g COD m−2 d−1, respectively, were applied to the filters. The filters did not clog and had good effluent removal capabilities for 274 and 190 days, respectively. However, the 0.3 m-deep filter did experience a reduced performance towards the end of the study period. In the 0.3 and 0.4 m-deep filters, the effluent COD and SS concentrations were less than 86 and 31 mg L−1, respectively, and nitrification was nearly complete in both these columns. Ortho-phosphorus (PO4-P) removal in fine sand and laterite ‘upflow’ filters, receiving effluent from the 0.3 m-deep filter, was 10% and 44%, respectively

Effects of plants development and pollutant loading on performance of vertical subsurface flow constructed wetlands

The influent concentration has a great effect on nutrients removal efficiency in vertical subsurface flow constructed wetland systems, but treatment performance response to different C: N: P ratios in the influent are unclear at present. At the first growing seasons, the effects of the plants present or not, season, the different C: N: P ratio in influent condition and their interaction on treatment performances were studied in the planted or the unplanted wetlands in greenhouse condition. Each set of units was operated at hydraulic loading rates of 40 L/d. Low, medium and high-strength (100, 200, 400 mg/L of chemical oxygen demand or 20, 40, 80 mg/L total nitrogen) synthetic sewage were applied as influent. According to the first growing season results, the average removal efficiencies for the unplanted and the planted wetlands were as follows: chemical oxygen demand (44–58 % and 55–61 % respectively), total nitrogen (26–49% and 31–54 %) and total phosphorus (36–64 % and 70–83 %). The both wetlands system was operated as an efficient treatment system of highest average removal rates of both chemical oxygen demand and total phosphorus when medium-strength synthetic sewage were applied. When high strength synthetic sewage was applied, the planted wetlands usually had a higher nutrients removal rates than the unplanted over the study period. The plants grew well under any high loading treatment over the study period. Anyhow, it also proved that the wetland systems have a good capacity to treat different strength wastewater in greenhouse condition.

A microbial fuel cell–electro‐oxidation system for coking wastewater treatment and bioelectricity generation

AbstractBACKGROUND: Coking wastewater is generated from coal coking, coal gas purification, and by‐product recovery processes. Increased interest is being focused on finding more sustainably effective and energy‐efficient methods for treating this wastewater. In this work, a system termed microbial fuel cell‐electro‐oxidation (MFC‐EO) was developed for simultaneous coking wastewater treatment and bioelectricity generation.RESULTS: Raw coking wastewater was first treated using MFCs. Power production, removal of total chemical oxygen demand (TCOD) and total nitrogen (TN) reached 538 ± 9 mW m−2, 52 ± 1% and 50 ± 1%, respectively. Wastewater strength and phosphate addition were evaluated for the enhancement of power production and treatment efficiency. At the EO stage, the effect of current density and chloride concentration on pollutant abatement, current efficiency (CEEO) and energy consumption (ECEO) were investigated. The overall removal of TCOD and TN was 82 ± 1% and 68 ± 1%, respectively using the MFC‐EO process.CONCLUSIONS: A MFC‐EO process was developed for the first time for simultaneous bioelectricity generation and coking wastewater treatment. This study attempted to combine MFCs with a conventional EO process for coking wastewater treatment. Further strategies need to be investigated to optimize reactor configuration using low‐cost and highly efficient electrode materials. Copyright © 2009 Society of Chemical Industry