Application of Cost Criteria for Selection of Municipal Wastewater Treatment Systems

Analysis of economic data pertinent to the existing municipal wastewater treatment plants (MWTP) in Greece is presented. Thisinformation is important when budgeting for future plants. Thedata include land usage and the costs for construction, operationand maintenance of the form y = ax ^b, where a and b are calculated coefficients. Equations for cost and landuse were produced for specific systems. Personnel and energy aspects are analysed as they are major contributors to operationalcost. A life cycle analysis (LCA) of plants is undertaken. The results of such an analysis should suggest the most preferabletechnology under given circumstances. Thus, under high energy costs and low level of automation and operation, at low F/M ratios, conventional activated sludge systems are relatively notcost effective. In addition, for cost of land less than US$30 per m², waste stabilisation ponds are cost effective subjected to minor earthworks.     

Assessment of Luffa cylindrica as Support in Biofilms Reactors for the Biological Treatment of Domestic Wastewater

A simultaneous treatment of BOD, phosphorous and ammonia in artificial wastewater was carried out in biofilm reactors with Luffa cylíndrica as organic support and compared with PVC's support under variations of dissolved oxygen of 1.5 a 3.0 mg l^?1 in the same reactor. During semicontinous treatment, the removal of BOD (92.5%) with Luffa cilíndrica was higher than PVC support (80%). Nitrification only existed at levels of oxygen of 3 mg l^?1, showed in the effluent a final concentration of ammonium of 17 and 19 mg l^?1 for Luffa cilíndrica and PVC support, respectively. In reactors with Luffa cilíndrica a higher percentage of P removal (40%) was reached, while no elimination in reactors with PVC was observed. The formation of anaerobic-aerobic zones inside the natural support probably allowed the increase in the efficiency of removal of phosphorous. Oxidation of organic matter, P removal and nitrification can be achieved with the variation of oxygen inside of the same biofilm reactor using L. cylindrical as support material.     

新型高效反应器组合系统处理奶牛养殖场废水试验研究

选择一种新型高效反应器系统对奶牛养殖场废水进行处理试验研究,这种反应器系统主要包括两级组合生物巢厌氧反应器和砂式沼液处理池。试验结果表明,该系统处理奶牛养殖废水速度快,两级组合生物巢厌氧反应器水力停留时间（HRT）仅为15h,处理效率高,砂式沼液处理池结构简单,对生物巢厌氧反应器出水处理效果好。该新型高效反应器组合系统对化学需氧量（COD）、生化需氧量（BOD）、氨氮（NH3-N）和总固体悬浮物（TSS）的平均去除率分别为97.6%、98.2%、81.3%和98.1%,出水体积质量平均值分别为89.0、27.1、15.7mg·L^-1和64.9mg·L^-1,满足国家二级排放标准。     

Effect of Temperature on Bio-Kinetic Coefficients in UASB Treatment of Municipal Wastewater

Upflow anaerobic sludge blanket (UASB)reactors were used to treat municipal wastewater attemperatures of 6, 11, 15, 20 and 32 °C and athydraulic retention times (HRTs) ranging from 48 to 3 h overan operational period of approximately 860 days. The Monodmodel was used to evaluate substrate utilization. TheArrhenius model was used to calculate the activationenergies from which temperature coefficients weredetermined. It was found that the maximum specific substrateutilization rate constant (k) decreased from 0.387 d^-1(at 32 °C) to 0.041 d^-1 (at 6 °C). Thedecay rate constant (k_d), yield coefficient (Y_g),half velocity constant (K_s) and maximum specific growthrate (μ_m ) were also impacted by temperature in theUASB treatment of municipal wastewater.     

Synthetic Fibers as Indicators of Municipal Sewage Sludge,Sludge Products,and Sewage Treatment Plant Effluents

Because of concerns regarding health, safety, and aesthetics, a test that identifies the presence of sewage sludge or its products (biosolids) in commercial materials such as soil conditioners and composts would be useful. This test could also trace the effluent plume from a sewage treatment plant. We have discovered that synthetic fibers serve as such an indicator. Synthetic fibers are abundant in sludge, sludge products, and sewage treatment plant effluents. The fibers evidently are introduced from clothes-washing machines and survive the sewage treatment process. Synthetic fibers were identified using polarized light microscopy, which provided a simple, rapid method for determining the presence or absence of municipal sewage sludge or its products. False positives or false negatives have not occurred with any of the materials examined so far. We also monitored synthetic fibers in surface sediments of Huntington Harbor, Long Island, NY, a harbor receiving the effluent from a trickling filter sewage treatment plant. Fibers generally decrease in size and abundance with distance from the source. In Oyster Bay Harbor, Long Island, an advanced sewage treatment plant is operated with a final microfiltration step. Synthetic fibers are less abundant in the sediments of this harbor.     

Effect of Municipal Wastewater as a Wetland Water Source on Soil Microbial Activity

Microbial activity levels of two soil materials, excavated from a wetland and irrigated with municipal wastewater effluent or Missouri River water, were compared. The wastewater had twice the electrical conductivity and four times the sodium concentration as river water. We performed activity assays on the soils before leaching, immediately after leaching, and after harvesting plants. Gas chromatography was used to measure carbon dioxide (CO₂) evolved in soil samples incubated for 7 d. Activity was significantly reduced in preleached wastewater–irrigated soils compared with river water–irrigated soils. Immediately after leaching, activity significantly increased and was similar to river water–irrigated soils. Activity decreased slightly after plant harvest in postleached treatments. Increased activity after leaching may be related to decreased salinity and sodicity, which probably lowered osmotic pressure in the soil. Our study demonstrated that soil salinity and sodicity induced by wastewater irrigation decreased microbial activity, which may impact nutrient cycling and glycophytic vegetation communities in wetlands.     

Estimating Levels of Micropollutants in Municipal Wastewater

The evolution of microbial communities with increasing carbon tetrachloride concentrations was studied in two anaerobic columns containing sand and two different clay soils, one of which contained high levels of iron. Microbial communities were characterized through analysis of column effluents with denaturing gradient gel electrophoresis and quantitative polymerase chain reaction for archaea and eubacteria as inlet carbon tetrachloride concentrations were increased from 0.8 to 29 μM. Inhibition of microbial activity was observed in both columns, and was associated with the accumulation of chloroform at concentrations of 0.2 to 0.4 μM as inlet CT concentrations were increased to 2.4–3.0 μM in the low-iron clay column and approximately 16 μM in the iron rich clay column. Inhibition was indicated by decreasing rates of methanol and carbon tetrachloride degradation, decreases in effluent levels of DNA, and shifts in microbial communities of the columns. Even with the inhibition observed, in the iron-rich clay column CT degradation continued to the end of the study with inlet CT concentrations of 29 μM, in contrast to the low-iron clay column in which minimal CT degradation occurred once CT inlet concentrations exceeded 3 μM. The greater capacity for CT degradation in the column containing the iron-rich clay was hypothesized to be the result of reaction with biogenic ferrous iron produced by biological dissimilatory iron reduction.     

Bioremoval of Surfactant from Laundry Wastewater in Optimized Condition by Anoxic Reactors

Effects of ethanol and nitrate on linear alkyl benzene sulfonate (LAS) degradation were investigated using central composite design. At experimental design, removal of 99.9% was observed in batch reactors (1 L) with 9.8 to 41.2 mg L^?1 of LAS. The batch reactors were kept under agitation at 120 rpm and 30 °C. Ethanol (co-substrate) and nitrate (electron acceptor) were statistically significant factors (p?<?0.05) in surfactant removal. Optimal values were 97.5 and 88 mg L^?1 for ethanol and nitrate, respectively. LAS removal was kinetically investigated by varying surfactant concentration while using optimal values. Batch I (27 mg L^?1 LAS) exhibited greater degradation rate (K^LAS) (0.054 h^?1) in the presence of ethanol and nitrate. Nonetheless, in Batch II (60 mg L^?1 LAS), the K^LAS values decreased in those reactors probably due to inhibition by excess substrate for same concentrations of nitrate and ethanol added in reactors. As LAS concentration increased, the dominance of bacterial populations also increased, whereas diversity index decreased from 2.8 (inoculum) to 2.4 and 2.5 for reactors with both added nitrate and ethanol and those with only added ethanol, respectively. Probably, a selection of microbial populations occurred in relation to LAS concentration. The nitrate and ethanol, at able concentration, made it possible the induction of denitrifying microrganisms foward to LAS removal.     

Nitrogen Dynamics in Forest Soils after Municipal Sludge Additions

Nitrogen dynamics were assessed for a forested site in southern New Hampshire during the first and second growing seasons after surface application of an aerobically-digested, limed, liquid municipal sludge. Sludge was applied in June 1989, at 3.3, 6.9, and 14.5 M ha-1 (or 199, 396, and 740 kg TKN ha-1). Elevated net N mineralization (in situ buried bags) occurred in the organic and upper mineral soil horizons during the first two months after sludge application, but was similar to control levels thereafter. Net N mineralization was negligible at 30 and 60 cm soil depths. Foliar N concentration increased with sludge loading rates. Concentrations of NH4+ and NO3- in soil leachate were low, except in early fall when microbial activity was still high and plant demand was low. In trenched subplots where vegetative uptake was eliminated, NO3- concentrations in soil leachate (60 cm) rose to between 15 and 35 mg N L-1 in the first year and remained high in the second year. Other studies reported higher magnitudes of NO3- leaching from treated plots. These studies and the findings reported here shown the characteristics of the sludge being applied to land are at least as important as the physical and chemical characteristics of the site to which they are to be applied.     

兰州市城市污水处理厂污泥中重金属形态分布特征与潜在生态风险评价

通过现场调查采样及室内分析,研究了兰州市七里河安宁污水处理厂和雁儿湾污水处理厂污泥中重金属的形态分布特征,并对其进行了潜在生态风险评价。结果表明,污泥总体呈高有机质、高全N和有效P、高微量营养元素,且Cu、Zn、Cd、Pb、Ni5种重金属的含量均低于污泥农用控制标准,具有很好的农用价值。污泥中Zn、Cd、Pb主要以有机结合态和残渣态存在,而Cu、Ni可交换态所占比例较高,分别为14.95%和14.41%,不稳定态所占比例分别为41.12%和31.04%,表现出较高的生物活性和可利用性。七里河和雁儿湾污泥中重金属的潜在生态风险属于低度风险;Cd、Cu是污泥中重金属潜在生态风险的主要贡献者,在污泥处理处置时应引起高度重视。     

Wastewater Chemistry and Fractionation of Bioactive Phosphorus in Dairy Manure

Abstract

Because manure organic phosphorus (P) is environmentally bioactive, a novel in situ enzyme hydrolysis assay was developed to identify water soluble‐ and labile complexed P and mechanisms controlling P solubilization in dairy manure. Water‐extractable P averaged 16% (±14.8%) of total P of 107 manures collected across five northeastern states of the USA. Adding a multidentate ligand solubilized inorganic complexed P (15±8.3%) primarily associated with calcium (Ca) and magnesium (Mg). An additional organic fraction (35.9±15.6%) was hydrolyzable by fungal phytases. The assay was more revealing about on‐farm P management than just knowing total P; the water‐extractable P distribution was skewed to the left, and two thirds were <2500 mg kg^?1; bioactive and total P were normally distributed, differing extensively between farms with a range spanning an order of magnitude. The assay's simplicity and robustness over the wide range of manure characteristics may increase routine evaluation of whole‐farm accumulation of environmentally sensitive P forms.     

Optimization of Compatible Mixed Cultures for Liquid State Bioconversion of Municipal Wastewater Sludge

The filamentous fungal strains such as Penicillium corylophilum (P), Aspergillus niger (A), Trichoderma harzianum (T) and Phanerochaete chrysosporium (PC) isolated from its relevant sources (wastewater, sewage sludge and sludge cake) were selected for compatible/incompatible mixed cultures. Six combinations of P. corylophilum and A. niger (P/A); P. corylophilum and P. chrysosporium (P/PC); P. corylophilum and T. harzianum (P/T); A. niger and T. harzianum (A/T); A. niger and P. chrysosporium (A/PC); T. harzianum and P. chrysosporium (T/PC) were used to evaluate their potential performance as compatible/incompatible mixed culture for the treatment of municipal wastewater sludge in a bioconversion process. The results of the present study showed that the combinations of P/A, P/PC and A/PC showed compatible growth and the rest of the combinations (P/T, A/T and T/PC) were incompatible cultures. A maximum production of dry biomass and dry filter cake were recorded in the compatible mixed culture of P. corylophilum and A. niger (P/A). A maximum reduction of COD (90%) and a decreased filtration time of treated sludge was observed in the case of P/A microbial mixed culture. The pH value was also affected by the fungal cultures. Effective results were observed by using microbial mixed culture after four days of treatment compared to other treatments (2 and 6 days).     

Ecological Engineering of Bioreactors for Wastewater Treatment

Biological nutrient removal (BNR) systems remove carbon, nitrogen, and phosphorus from wastewaters through biodegradation of organic compounds, oxidation of ammonia-N to nitrate-N, reduction of nitrate-N to N₂ gas, and sequestration of phosphorus as polyphosphate. The microbial community in such systems is complex because it must contain heterotrophic bacteria capable of aerobic respiration, anaerobic respiration, and fermentation; specialized heterotrophic bacteria that can store polyphosphate; and autotrophic nitrifying bacteria that can withstand long periods without oxygen. Although the basic design principles for BNR systems are reasonably well established, it is becoming apparent that a greater understanding of the microbial interactions involved is required to increase system reliability. For example, although the environment established for the selection of phosphorus accumulating organisms was thought to give them a strong competitive advantage over other heterotrophic bacteria, this has turned out not to be the case. Rather, glycogen accumulating organisms can compete quite effectively in the same environment. Furthermore, BNR systems have suffered from problems with sludge settleability, even though many of the system characteristics are considered to be conducive to the suppression of filamentous bacteria. Finally, the use of molecular techniques has revealed that the autotrophic nitrifying bacteria are different from those that had been considered to be present. This paper reviews the microbial ecology of BNR systems, establishes how molecular biology techniques are changing our understanding of that ecology, and suggests ways in which engineering control can be exerted over community structure, thereby increasing the reliability of BNR systems.     

Evaluation of some Methods for Fish Canning Wastewater Treatment

A fish canning facility processes 1900–2000 tons of mackerel and sardine annually at arate of 10–15 tons per day for a total of 200 days yr^-1. This factory generates an average of 20 m³ of industrial wastewaters per day. The objective of our study, which was carried out on a bimonthly basisfrom December 1995 to November 1996, was to determine the overall pollutant load associated with this effluent in relation to the applicable Egyptian Standards and to propose methods for pollutant load reduction before discharging it to the local sewer. The methods were to benefit through the recovery of wasted organic load and transform it into an environmentally safe residue amenable for either immediate reuse or final disposal thereafter. Five chemical coagulation/flocculation treatments were tried using ferric chloride, alum, lime, ferric chloride and lime, and alum and lime. The best method involved the use of FeCl₃ and Ca(OH)₂ (0.4 g Fe L^-1 and 0.2 g Ca L^-1, respectively) which reduced the average influent BOD₅ from 989 to 204 mg L^-1, the COD from 1324 to 320 mg L^-1, TSS from 4485 to 206 mg L^-1, total protein content from 812 to 66 mg L^-1 and oil and grease from 320 to 66 mg L^-1. The separated dried precipitate averaged 50 g L^-1 which was found to contain 40% by weight recovered protein and 20% recovered fat. The solid was ideal for on-site reprocessing as animal feed. As well, the final effluent, if not discharged to the area sewer, was safe for controlled use in some irrigation applications or forestry projects at the desert area surrounding the factory.     

Evaluation of Vertical-Flow Constructed Wetlands for Swine Wastewater Treatment

In this study, the role of Cyperus sp. was evaluated for removal of pollutants from swine wastewater. Vertical-flow pilot scale constructed wetlands (CWs) operating with a hydraulic retention time (HRT) of 72 h were monitored in a greenhouse, located in Viçosa, Brazil. Significant differences were observed for the following parameters: Kjeldahl nitrogen, total phosphorus, alkalinity and electric conductivity, with averages removals of 37.5 and 28.5%, 55.9 and 44.4%, 30.2 and 25.6 and 26.1% and 22.9% (for planted and unplanted CWs, respectively). The rate of dry matter yield from Cyperus sp. was 7.5 g?m^?2 day^?1, and the nutrient uptake capacities were 21.8, 2.1, 14.0 and 0.9 g?m^?2 of N, P, K and Na, respectively. Evapotranspiration (2.7 mm day^?1) was statistically higher in the planted CWs. Plants in the CWs are important for achieving high nutrient removal.     

Copper,Zinc, and Lead Fractions in Soils Long-Term Irrigated with Municipal Wastewater

Long-term irrigation with municipal wastewater may lead, even in spite of intense farming, to an accumulation of organic matter, nutrient elements, and trace metals in soils. Excessive increases of heavy metals may pose a potential risk to the food chain and provoke restrictions for the further cultivation of sensitive crops. Copper (Cu), zinc (Zn), and lead (Pb) forms in soils under long-term irrigation (for 100–120 years) with treated wastewater of Wroclaw were investigated by using selective seven-step sequential extraction (procedure of Zeien-Bruemmer) for partitioning the metals into operationally defined fractions, likely to be released in solution under various environmental conditions. The largest fraction of Cu, Pb, and particularly Zn in nonirrigated (control) soils was strongly bound in a residual form, while the percentage of exchangeable and the most labile fractions were negligible. Total concentration of metals in irrigated soils was elevated, and significant redistribution of metals among phases was observed. Percentages of residual fraction of Cu and Pb were no more than 25% (Zn < 40%), while significantly increased contribution of fractions occluded on iron (Fe) oxides and organically bound Cu. Exchangeable and readily mobile forms of Zn are predominant zinc fractions in soils irrigated with wastewater.     

Ciprofloxacin Resistance in Domestic Wastewater Treatment Plants

The potential of domestic wastewater treatment plants to contribute for the dissemination of ciprofloxacin-resistant bacteria was assessed. Differences on bacterial counts and percentage of resistance in the raw wastewater could not be explained on basis of the size of the plant or demographic characteristics of population served. In contrast, the treated effluent of the larger plants had significantly more heterotrophs and enterobacteria, including ciprofloxacin-resistant organisms, than the smaller (p?<?0.01). Moreover, longer hydraulic retention times were associated with significantly higher percentages of resistant enterobacteria in the treated effluent (p?<?0.05). Independently of the size or type of treatment used, domestic wastewater treatment plants discharged per day at least 10¹⁰–10¹⁴ colony forming units of ciprofloxacin-resistant bacteria into the receiving environment.