Toxicity assessment of free form of heavy metals in aqueous media on earthworm Eudrillus eugeniae

Metals are found in free and also in combined forms. In order to get information on the effect of free forms of heavy metals on earthworms the aqueous extracts of metals were tested on earthworms both in individual form and also in combined form. Different concentrations, i.e. 1 ppm, 5 ppm, and 10 ppm, were selected arbitrarily and were used in the experiments. Metals like copper, cadmium, chromium, zinc and lead were used. Earthworms' Eudrillus eugeniae activity, i.e. their response to the toxicity of metals, was monitored continuously for 5 h. It can be concluded that free form/ionic form/dissolved form of heavy metals are more toxic for earthworms, concurrent with findings of workers who have drawn same inference during studies on aquatic organisms. Earthworms can serve as biomarkers for wastewater and sludge treatment studies as they have shown typical adverse body reactions and symptoms altogether different in reaction to each of the metals during aqueous medium studies. It can be inferred that, if earthworms are utilised for treating wastewater and sludges containing these five heavy metals, one can ascertain the presence of individual metal concentrations in the wastewaters and sludges by studying the typical body reactions of earthworms during the treatment.     

The Ruhrverband sewage sludge disposal concept in the conflict between European and German standards and regulations.

The Ruhrverband, acting as a water association responsible for integrated water resources management within the entire natural river basin of the Ruhr, operates a network of 83 wastewater treatment plants (WWTPs) and connected sludge disposal facilities. According to German regulations, the disposal of sewage sludge containing more than 5% of organic dry solids will be prohibited as of 1 June 2005. In Germany, the only future alternative to incineration will be the agricultural utilization of sludge. However, this way of sludge disposal is presently the subject of critical discussions in Germany because of the organic and inorganic toxic substances, which may be contained in sewage sludge, despite the fact that very stringent standards are to be met by agricultural uses. On the other hand, application of sewage sludge to agricultural land is explicitly supported by the European Sewage Sludge Directive 86/278/EEC. In the face of this controversial situation the Ruhrverband has initiated, in 2000, the development of a comprehensive and sustainable sludge and waste disposal concept for all wastewater facilities it operates in the entire Ruhr River Basin. The concept includes de-central sludge digestion and dewatering and subsequent transport to two central sludge incineration plants. It is expected that in future not more than 5% of all sludges produced in Ruhrverband's WWTPs will be used in agriculture. That means, the major part of 95% will have to be incinerated.     

Assessment of alkylphenols in wastewater treatment: do we comply with new directives?

The fate of various alkylphenolic compounds during wastewater treatment was studied at full scale in thirteen plants, selected in order to cover a wide range of treatment processes, sizes and countries. In-depth investigations consisted in the analysis of nonylphenols, short chained (n = 1, 2) but also long chained polyethoxylates in raw wastewaters, effluents, raw and treated sludges. The degradation of long chained polyethoxylates (APnEO) was shown, resulting in significant production of alkylphenols that concentrate in the sludges. Results show however that the pending Directive on spreading of sludge on land would be complied with in all cases. For the effluent, the EQS established within the WFD might not be satisfied in very critical situations where the dilution factor of the effluent in the river would be too small.     

正确的政策导向是发展可持续污泥处理技术的保障

对污泥厌氧消化技术在国内外的应用及发展情况作了简单介绍.通过与其他污泥处理工艺对比,分析了污泥厌氧消化的优缺点、污泥厌氧消化工艺的费用与收益.指出污泥厌氧消化工艺是一种可持续的实用技术,理应成为城市污水处理厂污泥稳定化处理的首选工艺.认为应对现行的《城市污水处理及污染防治技术政策》进行修改,鼓励有条件的污水处理厂在选择污泥处理工艺时优先考虑厌氧消化技术.     

Polyhydroxyalkanoates (PHA) production using wastewater as carbon source and activated sludge as microorganisms.

Activated sludge from different full-scale wastewater treatment plants (municipal, pulp and paper industry, starch manufacturing and cheese manufacturing wastewaters) was used as a source of microorganisms to produce biodegradable plastics in shake flask experiments. Acetate, glucose and different wastewaters were used as carbon sources. Pulp and paper wastewater sludge was found to accumulate maximum concentration (43% of dry weight of suspended solids) of polyhydroxy alkanoates (PHA) with acetate as carbon source. Among the different wastewaters tested as a source of carbon, pulp and paper industry and starch industry wastewaters were found to be the best source of carbon while employing pulp and paper activated sludge for maximum accumulation of PHA. High concentration of volatile fatty acids in these wastewaters was the probable reason.     

Detection of fatty acid beta-oxidizing syntrophic bacteria by fluorescence in situ hybridization.

A new 16S rRNA-targeted oligonucleotide probe, specific for the cluster of fatty acid beta-oxidizing syntrophic bacteria of the family Syntrophomonadaceae was designed for fluorescence in situ hybridization. This probe was evaluated with target as well as non-target cultures. Moreover this probe was assessed with butyrate and oleate degrading enrichment cultures and methanogenic sludges from full-scale plants. The results showed that the probe revealed the presence of fatty acid beta-oxidizing syntrophic bacteria in some of the samples analyzed. However, cell quantification was possible only in enrichment cultures and in a flocculent sludge from a reactor that treats lipid-rich wastewaters, but not in methanogenic granular sludges from upflow anaerobic sludge blanket reactors.     

Dedicated land disposal of wastewater sludge in south africa: leaching of trace elements and nutrients.

Most of the wastewater treatment facilities in South Africa (80%) dispose of their sewage sludge on dedicated land disposal (DLD) sites. The impact of this practice on the environment is believed to be negative, but very little research has been carried out to determine the extent of the damage to the soil and water resources. Forty wastewater treatment facilities using DLD, with different soil properties, application techniques, metal concentrations and period of sludge application, were studied. Soil and groundwater samples were collected at each of the selected facilities. Three extraction methods (aqua regia, NH4EDTA and NH4NO3) were used and samples were analysed for total N, P and K, pH, organic carbon and their metal content (Cr, Co, Ni, Cu, Zn, Cd, and Pb). Some degree of leaching of the heavy metals (especially Co and Ni) occurred at some of the sampling sites and the average depth of leaching was 100-200 mm. Deeper than 300 mm, the metal concentrations in most soil samples reached background concentrations. Seven of the nine groundwater samples that could be obtained had high NO3 concentrations (> 6 mg L(-1)). Statistical analyses of the data indicate no significant differences between sludge type (wet or dry) and leaching, or age of the disposal sites and leaching. Taking into account the age of the disposal sites, the frequency of sludge application and the metal load of the sludge, the depth of leaching is surprisingly shallow in most soils, in spite of the low soil pH(H2O) and clay content.     

Comparison of extracellular polymeric substances (EPS) extraction from two different activated sludges

The characteristics of extracellular polymeric substances (EPS) extracted with five different extraction protocols from two different activated sludges were studied. The results showed that the major EPS constituent extracted by centrifugation was protein for the sludge in sequencing batch reactor treating chemical wastewater, and nucleic acid for the sludge in moving bed biofilm reactor treating synthetic urban wastewater. The order of EPS extraction amounting from the two sludges was formaldehyde + NaOH > formaldehyde + heating > EDTA > heating > centrifugation. The different extraction methods, the wastewater type, and activated sludge source greatly affected the amount and composition of EPS. The chemical extracted methods were more effective than the physical methods in extracting EPS for the two sludges. Moreover, formaldehyde combined NaOH was most effective in extracting EPS for the two sludges. However, chemical extraction could contaminate the EPS solution, which was pointed out by infra-red analysis and was also proved by cell lyses during EPS extraction and carrying over of the chemical extractant. Therefore, this study highlights that the choice of EPS extraction method should consider both the extraction yield and content and the contamination of extracting reagents to the EPS solution. The extraction procedures should be optimized and most effective.     

Long term experience with the nutrient limited BAS process for treatment of forest industry wastewaters.

The nutrient limited biofilm-activated sludge (BAS) process was developed with the aim to ensure maximum biological treatment efficiency in combination with good process stability, low sludge production and minimum effluent concentration of nutrients. The first full scale nutrient limited BAS (NLBAS) processes were implemented at S?dra Cell V?r? and Stora Enso Hylte in 2002. Since then another three full scale installations have been built. The aim of this study was to investigate and summarise the long-term treatment results, process stability, sludge production and sludge characteristics for the five full scale NLBAS processes. It was of particular interest to compare the nutrient limited operating mode with regard to the different types of production and wastewater that the mills represent (kraft, TMP and newsprint, bleached CTMP). The study showed that after the initial start-up period, which varied from a couple of weeks to three to four months, all plants meet their respective discharge limits. The sludge production for the different plants varies between 0.07 and 0.15 kg TSS/kg COD and the sludge characteristics are with few exceptions excellent. In conclusion, the nutrient limited BAS process is suitable for both upgrades and new installations of biological treatment for different types of forest industry wastewaters.     

Role of syntrophic microbial communities in high-rate methanogenic bioreactors

Anaerobic purification is a cost-effective way to treat high strength industrial wastewater. Through anaerobic treatment of wastewaters energy is conserved as methane, and less sludge is produced. For high-rate methanogenesis compact syntrophic communities of fatty acid-degrading bacteria and methanogenic archaea are essential. Here, we describe the microbiology of syntrophic communities in methanogenic reactor sludges and provide information on which microbiological factors are essential to obtain high volumetric methane production rates. Fatty-acid degrading bacteria have been isolated from bioreactor sludges, but also from other sources such as freshwater sediments. Despite the important role that fatty acid-degrading bacteria play in high-rate methanogenic bioreactors, their relative numbers are generally low. This finding indicates that the microbial community composition can be further optimized to achieve even higher rates.     

An integrated electro-chemical and natural treatment system for industrial water pollution control.

Experiments were conducted to test the feasibility of applying an integrated electro-chemical (EC) and natural treatment system for treatment of some industrial wastewaters. The EC process was found to be very effective in removing lead, a model heavy metal from some wastewaters. Within 20 minutes of operation time, 5 to 10 A of electric current and specific surface area of electrode of 46.51 m2/m3, the lead concentrations in the wastewaters were reduced from 35-100 mg/l to less than 1 mg/l. Based on a kinetic model developed from the experimental data, the important parameters for the EC process were found to be electric current, specific surface area of electrode, and operation time. From scanning electron microscopic and X-ray diffractometric (XRD) analysis, the EC sludge samples were found to compose mainly of maghemite (Fe2O3), magnetite (Fe3O4), and laurionite (PbClOH), suitable for disposal to secure landfills. Two pilot-scale constructed wetlands (CW) in series, a model natural treatment system, were employed to treat wastewaters of an industrial estate in Thailand. At organic loading rates of 57-140 kg BOD/hectare-year, these constructed wetlands were able to reduce BOD from 90 to 4 mg/l, while suspended solids, total nitrogen and total phosphorus were reduced from 100 to 10 mg/l, 24 to 4.6 mg/l and 7 to 1.5 mg/l, respectively, during the summer season. These results demonstrated technical feasibility of CW in removing organic and other pollutants contained in this industrial wastewater.     

Phytotreatment of sludges (Phragmites australis) for their reuse in the environment

The aim of this study is the evaluation of the agronomic characteristics acquired by a phytotreated sludge coming from a wastewater treatment plant (WWTP) located in Tuscany (central Italy). The chemical characterization showed values which are within the Italian legislation limits for mixed composts. From an agronomic point of view, the sludge did not present a level of phytotoxicity, as shown by the germination index (GI% = 77). Furthermore, pathogen compounds are inexistent (Escherichia coli < 1,000 CFU/g). Different substrates (obtained by mixing the sludge with sandy agronomic soil - 0.5% w/w, 1% w/w, 2.5% w/w and 5% w/w) were prepared in order to evaluate the best mixture performance in terms of water retention capacity and plant growth. No significant differences were observed for all sludge mixtures. Different plants were tested in plots (Lepidium sativum, Cucumis sativus and Avena sativa). The best plant adaptation, measured as dry biomass production, was observed for Avena sativa. The results obtained underlined that the phytotreatment of sludge can bring about the transformation of sewage sludges into organic products that are reusable in agriculture, if previously mixed with other appropriate materials and taking into account their heavy metal content.     

Water reuse for irrigation from waste water treatment plants with seasonal varied operation modes.

Irrigation periods are usually limited to vegetation periods. The quality requirements for treated wastewater for disposal and for reuse are different. The reuse of water for irrigation allows partly the reuse of the wastewater's nutrients (N and P). Outside the irrigation period the water must be treated for disposal, thus nutrient removal is often required in order to avoid detrimental effects on the receiving surface water body. Only wastewater treatment plants with different operation modes for different seasons can realise these requirements. The nitrification is the most sensitive biological process in the aerobic wastewater treatment process. At low water temperatures the nitrifying bacteria need several weeks to re-start full nitrification after periods without NH4-removal. Therefore it is necessary to develop options for waste water treatment plants which allow a fast re-start of the nitrification process. Based on theoretical considerations and computer simulations of the activated sludge treatment process, one possibility for implementing a wastewater treatment plant with different seasonal operation modes is evaluated.     

Upgrading of existing aerobic plants with the LUCAS anaerobic system based on full-scale experiences.

It has been demonstrated that the combination of anaerobic-aerobic treatment is the best technological and economical solution for the treatment of high loaded wastewater. Where in the past aerobic treatment systems were still very acceptable due to the very good treatment efficiency, simplicity and robustness of the technology, this has, in most cases, been changed due to very stringent sludge disposal legislation. The anaerobic pretreatment takes care of approximately 80-90% of the overall treatment efficiency at high loading rates and low sludge production and low energy costs. The aerobic posttreatment takes care of the absolute high removal efficiency and nitrogen and phosphorus removal. Because of the low organic loading rate of the aerobic posttreatment also in this stage the sludge production is low. The combination of anaerobic-aerobic treatment results in a compact system capable of reaching high treatment efficiency at low sludge production and lower energy consumption. Waterleau Global Water Technology has developed LUCAS anaerobic-aerobic system that combines an Upflow Anaerobic Sludge Blanket (UASB) reactor with an aerobic, constant-level cyclic activated sludge system, which is very suitable for the treatment of high loaded wastewaters in general and brewery waste water in particular. It has been proven from several full scale upgrading projects that the UASB system is best suitable for implementation in the aerobic plants that have to be extended in capacity.     

Sustainable sludge management in developing countries.

Worldwide, unsanitary conditions are responsible for more than three million deaths annually. One of the reasons is the low level of sanitation in developing countries. Particularly, sludge from these regions has a high parasite concentration and low heavy metal content even though the available information is limited. Different issues needed to achieve a sustainable sludge management in developing nations are analysed. Based on this analysis some conclusions arise: sludge management plays an important role in sanitation programs by helping reduce health problems and associated risks; investments in sanitation should consider sludge management within the overall projects; the main restriction for reusing sludge is the high microbial concentration, which requires a science-based decision on the treatment process, while heavy metals are generally low; adequate sludge management needs the commitment of those sectors involved in the development and enforcement of the regulations as well as those that are directly related to its generation, treatment, reuse or disposal; current regulations have followed different approaches, based mainly on local conditions, but they favour sludge reuse to fight problems like soil degradation, reduced crop production, and the increased use of inorganic fertilizers. This paper summarises an overview of these issues.     

The role of iron and aluminium in digestion and odor formation.

The role of iron and aluminium in determining volatile solids reduction and odors from anaerobically digested, dewatered sludge cakes was evaluated from data collected from a variety of wastewater treatment plants. It was found that volatile solids reduction generally increased as the iron content of the sludge increased. It was also observed that odors increased with increasing iron. No correlation with aluminium or divalent cations was found. Based on these data it appears that the volatile solids reduction by anaerobic digestion is not useful for predicting the odors from anaerobically digested sludges.     

Performances of three R-AN-D-N wastewater treatment plants in the Czech Republic.

The evolution of Czech standards requires higher efficiency of nutrient removal from municipal wastewaters. At the beginning of the last decade of 20th century, a new activated sludge configuration called R-AN-D-N process has been described, successfully tested and now largely used at several wastewater treatment plants (WWTP) in the Czech republic. The main feature of the R-AN-D-N process is the introduction of a regeneration zone in sludge recycle, which enables to increase sludge age in the system without any substantial increase in WWTP volume. Performances of three Czech large WWTP with R-AN-D-N configuration have been monitored and compared within a period of one and a half years. The results confirmed excellent nutrient removal efficiency for wastewaters with different proportion between sewage and industrial effluents. Two of three monitored WWTP received wastewaters from breweries (Budweiser and Pilsner Urquell). The settleability of activated sludge from all three WWTP was correct, with SVI values usually ranging from 50 to 150 ml/g. Monitoring of sludge composition indicated proliferation of several filamentous bacteria, particularly types 0581, 0092 and M. parvicella. No severe bulking events were observed. Finally, the operational costs expressed in CZK (Czech crown: 1 CZK = [see symbol in text]0.0322) per cubic metre of treated sewage or per capita amounts respectively from 2.24 to 6.52, and from 285 to 342.     

Occurrence and fate of heavy metals in large wastewater treatment plants treating municipal and industrial wastewaters.

This paper deals with a detailed study on the occurrence and fate of heavy metals (plus As, Fe and Al) in five Italian large wastewater treatment plants treating municipal and industrial wastewaters. The study showed that some of the compounds (As, Hg and Cd) were present at trace levels, while others were dispersed in a broad range of concentrations and were sometimes under the detection limit. The occurrence followed the order Hg = As < Hg < Pb < Ni < Cu < Cr < Fe < Zn < Al. Metals were mainly present bound to particulate organic matter in municipal wastewaters while they were often present in soluble phase in industrial wastewaters. Some heavy metals, like Hg and Pb, showed clear correlations with Al and Fe, therefore the last could be used as control parameters. Metals were removed with good efficiency in the treatment works, with the order As < Cd = Cr = Zn < Pb < Hg < Ni = Al < Cu < Fe. Metals then concentrated in waste activated sludge and accumulated after sludge stabilisation because of volatile solids degradation, therefore some problems may arise with limit for agricultural application, in particular for Hg, Cd and Ni.     

Towards a complete recycling of phosphorus in wastewater treatment--options in Germany

Global reserves of mineral phosphorus are finite and the recycling of phosphorus from wastewater, a significant sink for phosphorus, can contribute to a more sustainable use. In Germany, Switzerland, and the Netherlands, an increasing percentage of municipal sewage sludge is incinerated and the contained phosphorus is lost. This paper reviews current technologies and shows that a complete phosphorus recovery from wastewater is technically feasible. Depending on the composition of the sewage sludge ash (SSA), there are various options for phosphorus recovery that are presented. Iron-poor SSAs can be used directly as substitute for phosphate rock in the electrothermal phosphorus process. SSAs with low heavy metal contents can be used as fertilizer without prior metal elimination. Ashes not suitable for direct recycling can be processed by thermal processes. Operators of wastewater treatment plants can additionally influence the ash composition via the selection of precipitants and the control of (indirect) dischargers. This way, they can choose the most suitable phosphorus recovery option. For sewage sludge that is co-incinerated in power plants, municipal waste incinerators or cement kilns phosphorus recovery is not possible. The phosphorus is lost forever.     

污泥活性炭的制备及其用于重金属废水处理的研究进展

城市污水处理厂在处理污水的同时会产生大量的污泥,其含有大量有机物和有害物,性质不稳定,易腐化,如果处理不当,将会造成严重的环境污染和资源浪费.用城市污水处理厂污泥制备活性炭是20世纪80年代后期出现的一种新型利用途径,因其制备成本低,活性炭用途广泛,可以用于污水处理去除有毒有害物质,具有良好的环境效益和社会效益,引起国内外研究人员的关注.而有毒重金属对环境的严重威胁正逐渐成为全球性问题,活性炭吸附法是一种常用来处理重金属废水的方法.综述了国内外污泥制备活性炭的工艺方法,及在这些制备方法基础上对重金属废水的处理研究.