Particle and micro-organism removal in conventional and advanced treatment technology

All international drinking water quality standards can be divided into four groups

• -(micro)biological: bacteria, viruses, cysts, higher organisms, etc.
• -toxicological: THM, AOX, pesticides, solvents, etc.
• -organoleptic (esthetic): taste, odor, color, turbidity, etc.
• -operational: DOC, AOC, pH, Ca²⁺, HCO₃⁻ , CI⁻, SO₄²⁻, etc.

The philosophy on drinking water treatment focuses on the removal of all the undesired species, dissolved and undissolved, available in raw water, in such a way that no new undesired compounds are introduced during treatment such as Al, Cl₂, THM, AOX and AOC or during distribution such as Pb, Cu, Cd and asbestos. Special attention is paid to the removal of organic and inorganic colloids and of micro-organisms. Microbiologically stable water during storage and distribution can be realized by removal of nutrients (DOC, AOC) without the use of chlorine of chlorine products.As an example the treatment systems of the Amsterdam Water Supply based on the relatively very polluted raw water of the river Rhine are described. For future expansion of the production capacity membrane processes such as hyperfiltration (HF), electrodialysis reversal (EDR) and ultrafiltration (UF) are investigated.Results are shown on conventional and advanced technology concerning: final water quality, natural and environmental protection, process stability and costs per m³.     

Survey of filamentous populations in nutrient removal plants in four European countries

A joint EU research project aimed at solving activated sludge bulking in nutrient removal plants was initiated in 1993. The project started with a survey of the size and composition of the filamentous population in nutrient removal plants in Denmark, Germany, Greece and the Netherlands.The results show that biological nutrient removal process conditions indeed favour filamentous microorganisms in their competition with floc forming organisms. An increase in the size of the filamentous population resulted in a deterioration of the settling properties of the biomass, except for plants with Bio-P removal conditions. It is assumed that in the latter case the dense clusters of Bio-P bacteria increase the weight of the flocs, and compensate for the effect of the larger number of filaments.Although exceptions frequently occur, the following sequence in decreasing filamentous organism population size was observed for the process conditions indicated:

• -completely mixed + simultaneous denitrification;
• -completely mixed + intermittent aeration/denitrification;
• -alternating anoxic/oxic process conditions, with an anaerobic tank for biological phosphate removal (Bio-Denipho);
• -alternating anoxic/oxic process conditions (Bio-Denitro);
• -predenitrification

The surveys provided little information about the effect of nutrient removal in plants with plug flow aeration basins. Simultaneous precipitation with aluminium salts nearly always resulted in a low number of filaments and a good settling sludge.The size of the filamentous organism population showed a seasonal pattern with a maximum in winter/early spring and a minimum during summer (in Greece: during autumn). This seasonal variation is primarily caused by the effect of the season on the population sizes of M. parvicella, N. limicola and Type 0092.M. parvicella is by far the most important filamentous species in nutrient removal plants. In Denmark only, Type 0041 also frequently dominates the filamentous population, but seldom causes severe bulking. Considering their frequency of occurrence, approx. 10 other filamentous micro-organisms are of minor importance. Growth of some of these species, viz. those which use soluble substrate, can be prevented by the introduction of Bio-P process conditions.M. parvicella and Type 0041 (and probably also Actinomycetes and the Types 1851 and 0092) seem to compete for the same substrates i.e. the influent particulate fraction. Most of the differences in composition of the filamentous microorganism population can be explained by whether or not premixing of influent and recycled sludge is used. In general, premixing for a short period of time followed by anoxic conditions favours Type 0041. M. parvicella seems to proliferate if the particulate fraction is first hydrolysed or if it enters the plant via an oxic zone. It is concluded that bulking in nutrient removal plants is mainly caused by filamentous species requiring the particulate fraction for their growth.     

Remediation of contaminated sediments in Oslo Harbour,Norway

During the past 60–70 years, contaminated sediments from local rivers have been settling in the harbour basin of Oslo. This contamination, combined with that from other harbour activities, has developed into a serious pollution problem with both organic and inorganic contaminants. Since 1992 dredging activities have been restricted until the effect of dredging was determined and a safe disposal was found for the sediments. Because of this restriction, a conflict situation arose in terms of decreasing sailing depths, and dispersal of large quantities of contaminated sediments into the water column each day from ship traffic. A complete plan of action to remediate Oslo Harbour was started in 1994 and delivered to the State Pollution Control Authority (SF1) in August 1996. An evaluation of environmental risks connected to the remediation work has been carried out along with the determination of the requirements for the monitoring programme during and after the work. Preliminary evaluation of dredging techniques indicates that mechanic/hydraulic equipment will cause the least dispersion of sediment. Several options for treatment of the sediments have been evaluated. Study results point out that conditioning prior to disposal of the sediments in a confined disposal site in the harbour area, is the most cost effective solution. Seven disposal sites with a capacity of 0.5 mill. m³ have been identified. Two of the sites are integrated with a subsea road tunnel crossing the harbour basin. The other disposal sites will serve as new dock area after closure.     

The Incidence of Deformities in Chironomus spp. from Port Hope Harbour,Lake Ontario

Chironomus spp. larvae collected from sediments in the harbour at Port Hope, Ontario, had a greater incidence of mouth part deformities in the more heavily polluted inner harbour area (83%, 33 of 40 individuals) than in the outer harbour (14%, 1 of 7 individuals). Port Hope Harbour, the site of radium and uranium refining operations since 1933, is contaminated by ²³⁸U and (to a lesser extent) ²³²Th decay chain radionuclides and several trace metals. This difference suggests that deformities are related to the areal extent of contamination. An estimated dose rate of 1 mGy/day in chironomids suggests that radiation may be a significant factor in the induction of deformities; however, heavy metals and elevated water temperatures may also be involved.     

Monitoring of environmental effects and process performance during biological treatment of sediment from the Petroleum Harbour in Amsterdam

A full-scale (470 m³) process for biological treatment of dredging spoil from the Petroleum Harbour in Amsterdam has been monitored during a pilot project. The dredging spoil was heavily polluted with polycyclic aromatic hydrocarbons (PAH) and mineral oil. The remediation chain involved dredging, transport of dredged spoil, hydrocyclone separation, froth flotation of the coarse particles, and biological treatment of the silt fraction (<20 μm) in stirred bioreactors. The independent monitoring was aimed at recording the environmental effects, product quality and performance of the biological process.Hydrocyclone separation (cut point 20 m) resulted in two bulk streams: 65% sand and 30% silt (based on total dry weight of the input). The sand was cleaned and could be reused as building material. PAH and mineral oil were successfully concentrated in the silt fraction (<20 μm), which was treated biologically. Biological treatment during continuous feeding of fine fraction, at a residence time of 8–10 days for the entire bioreactor system, resulted in considerably reduced mineral oil and PAH contents. Furthermore, the leaching of organic contaminants was reduced, as well as the ecotoxicity. The obtained silt product however did not meet the demands, and had to be landfilled. Minor emissions of contaminants were measured in wastewater and offgas. The energy and chemicals consumption were acceptable.The biological process appears to be promising for the treatment of less-severely contaminated dredged material.     

A new formula for turbulent-flow velocity and an explanation of A. P. Zegzhda’s experiments

1. The basic influence exerted by hydraulic grade, and, as a consequence, Froude number, on the value of the coefficient of hydraulic resistance is disclosed; this is reflected by formulas (16) and (18), and has found confirmation in field investigations [3], and in Zegzhda's experiments.
2. In the design of canals, the coefficient of hydraulic resistance should be determined by calculation as a function of the grade and dimensions of the flow, and not assigned as a function of the frequency with which the surface of the channel is treated.

     

GENOTOXICITY IN CHIRONOMUS KIIENSIS (CHIRONOMIDAE: DIPTERA) AFTER EXPOSURE TO POLLUTED SEDIMENTS FROM RIVERS OF NORTH PENINSULAR MALAYSIA: IMPLICATION FOR ECOTOXICOLOGICAL MONITORING

Rapid industrialization and urbanization has led to increasing input of chemical contaminants into the aquatic environment of Malaysia. Despite the threat civilization poses to the biota, there are still very few relevant studies on ecotoxicological testing of river ecosystems. To overcome this knowledge gap, we examined lethal and genotoxic effects of sediments from different rivers of the northern Malaysia against Chironomus kiiensis, a group well represented in the aquatic fauna of this region. We exposed the larvae to sediments from Selama River (SR), Permatang Rawa River (PRR) and Kilang Ubi River (KUR) at various durations (0, 6, 12, 24 and 48 h). The larval mortality was monitored, whereas DNA damage in survivors' cells was determined using the comet assay. Pollution level indexed by the amounts of heavy metals and other organic contaminants in the sediment showed progressive increases from SR to PRR to KUR. Highly polluted sediments (PRR to KUR) were detrimental to C. kiiensis larvae, most of which did not survive following exposure for long periods. DNA analyses revealed greater damages in nuclei derived from larvae maintained on polluted sediments, in particular, those from KUR. The effects on the genomic material of C. kiiensis larvae occurred in a time‐dependent manner, with damage level increasing as exposure time progressed. Our results highlight the genotoxic properties of polluted sediments. More importantly, this study showed that C. kiiensis larvae could respond to different levels of pollution with respect to exposure time. It is concluded that C. kiiensis larvae is a potential candidate for river ecotoxicological monitoring. Copyright © 2012 John Wiley & Sons, Ltd.     

铀矿区地下水污染治理与修复技术研究进展

在总结近年来国内外铀矿区地下水污染治理与修复技术最新进展和已有成果的基础上,评述物理化学修复 技术,生物修复技术及可渗透反应墙技术基本理论、实际案例和未来发展前景。当前铀矿区地下水污染的原位治 理与修复技术以实验室研究为主,缺乏对实际铀矿区地下水污染治理与修复的工程实践,如何结合实际铀矿区水 文地质条件和污染特征开发绿色、高效、低碳的治理与修复技术,是未来铀矿区地下水污染治理修复的重要发展 方向。     

Design of a solvent extraction process for PAH-contaminated sediments: The wau-acetone process

Solvent extraction is one of the possibilities to clean-up polluted sediments. It is especially attractive when the sediment mainly consists of clay particles polluted with contaminants which are not, or not easily, biodegradable. Using acetone as extracting agent the extraction process has been investigated at laboratory scale for treating sediment of the Petroleum Harbour in Amsterdam. This sediment is characterised by a substantial percentage of particles with diameter < 63 μm, a high percentage of organic matter (about 12% on dry matter basis), a high concentration of PAH (500–2,000 mg total EPA-PAH per kg dry matter) and a high concentration of mineral oil (6,000–10,000 mg/kg dry matter). Based on the laboratory scale experiments a process design has been made of a complete solvent-extraction process with acetone. The main process steps in this design consist of a countercurrent flow extractor, a separator for the sediment, a post-treatment step to remove residual acetone from the sediment, a distillation column to recover the acetone for reuse and to concentrate the pollutants and a polishing step for the water to be discharged. The sediment treatment costs with this system are estimated at 115 NGL per tonne dry matter to be treated.     

Organic halogen,heavy metals and biological activities in pristine and pulp mill recipient lake sediments

In order to create a basis for prognosing future intrinsic remediation potential of past pollution by pulping industry, we analyzed biochemical activities and levels of pollution in sediments dated with ²¹⁰Pb and ¹³⁷Cs. A small pristine forest lake and a pulp mill recipient area of a large oligotrophic Lake Saimaa were test sites. Sediment concentration of EOX ranged from 40 to 130 μg Cl (g d.w.)⁻¹ in the pristine lake and from 770 to 4700 μg Cl (g d.w.)⁻¹ in the pulp mill recipient area and the C:Cl (w/w) ratio of sediment organic matter ranged from 2000 to 5100 and 42 to 230, respectively. The organic matter in 10 to 20 years old pulp mill recipient sediment was mainly of waste water origin. The activity gradients of β-glucosidase, butyrate-esterase, methane oxidation potential and endogenous respiration from surface to deeper layers were less steep in polluted than in pristine sediment. Methane oxidation potential was 120 μmol CH₄ d⁻¹ (g C)⁻¹ at the sediment surface of pristine lake sediment and 26 μmol CH₄ d⁻¹ (g C)⁻¹ at the polluted site, endogenous respiration rates of the surface sediment were 670 and 310 μmol CO₂ d⁻¹ (g C)⁻¹, respectively. In the most polluted layer we found a depressed potential for methane oxidation, inhibition of phosphatase and butyratelipase activities and moderately increased induction ratio of β-galactosidase to phosphatase in the SOS-Chromotest strain E. coli PQ 37. The results suggest that at the concentrations observed these effects in the sediment were not due to heavy metals.     

Application of a numerical model for circulation,temperature and pollutant distribution in Hamilton Harbour

The restoration of Hamilton Harbour, from an environmental standpoint, is a current concern for the agencies involved with remediation efforts in the harbour. Estimates of circulation and mixing are needed to assess the fate and transport of water quality constituents in the harbour. A three-dimensional hydrodynamic modeling system (ELCOM) is used to study the circulation and thermal structure in the harbour. The model results were compared with profiles of temperature at several moorings and currents and water levels in the harbour. The model showed considerable skill in reproducing the thermal structure, surface currents and water levels. Mean summer circulation in the harbour showed two counter-rotating gyres occupying the harbour. The model produced harbour-lake exchange characteristics are in agreement with previous studies. Simulations using passive tracers qualitatively agreed with chemical tracer studies conducted near a sewage treatment plant outfall. The accuracy of these simulations suggests that the model is capable of describing flow and transport of material required for detailed water quality simulations.     

In situ source zone sediment mixing coupled to groundwater biostimulation to enhance phenol natural attenuation

Phenol is an industrially key compound that has a wide range of applications and also one of the most commonly found toxic pollutants in wastewaters and groundwater. This paper demonstrates the applicability of in situ remediation at a deactivated industrial site using source zone excavation and sediment mixing associated with nutrients delivery into groundwater. Sediment excavation and mixing displaced the entrapped source zone enhancing mass transfer into groundwater and contaminant bioavailability. A nutrient solution prepared with nitrate, phosphate, sodium hydroxide and hydrogen peroxide was continuously delivered into groundwater to stimulate biodegradation and restrict plume migration. The observed correlation between phenol-dependent Enterobacteriaceae concentrations throughout the remediation time frame supported circumstantial evidence of biodegradation. Phenol concentration in groundwater (up to 1,300 mg/L) was reduced >99% after 5 months following remediation and remained under the established site specific target level (4 mg/L). Nitrate and phosphate concentrations returned to background concentrations levels at the end of the remediation. Overall, the proposed in situ remediation scheme was effective to remediate this particular aquifer contaminated with phenol for over 20 years.     

Chances for biological techniques in sediment remediation

Biological techniques can be applied in remediation of sediments contaminated with organic pollutants, such as mineral oil, PAH, PCB and chlorobenzenes. Within the period of 1989–1997 several techniques were developed from laboratory to full-scale. The chances for bioremediation lay in the relatively small environmental impact and the low costs of the techniques. Little energy is required, no emissions to soil or air occur and the natural structure of the sediments is not destroyed. The costs vary between 45 (landfarming) and 70 (reactors) Dutch Guilders per ton dry weight. The quality of the product to meet the legal standards for re-use was achieved for some, but not all, of the sediments. However, bioassays and leaching tests showed that bioremediation strongly reduces the ecotoxicity and dispersion risks of the material. Further research of the actual risks, accompanied by policy development of the standards for re-use, might increase the number of different types of sediments which can be successfully remediated by biotechnology.     

Historical Records of Metal Pollution in Sediments of Toronto and Hamilton Harbours

The sediments of Hamilton and Toronto Harbours contain some of the oldest records of metal pollution in the Great Lakes basin. The fluxes of Cd, Cr, Cu, Ni, Pb, Zn, Fe, and Mn into the two harbours have been estimated from the analyses of core samples dated by the Pb-210 technique. The contrasting metal levels in the two harbour sediments are viewed in relation to the differences in the disposal strategies of the dredged spoils and the sources of metal pollution in the harbours. The Zn and Fe concentrations of 5 to 8 mg g^?1 and 10 to 13 % dry wt. in Hamilton Harbour sediments, which are among the highest recorded in any harbour, can be related to effluent discharges from the large local iron and steel plants. An inventory of the sources and sinks of pollutant metals in Hamilton Bay shows a substantive export of the metals to Lake Ontario.     

Characterisation of PAH-contaminated sediments in a remediation perspective

To support the choice of a remediation technique for the decontamination of PAH contaminated dredged sediments a characterisation test is needed, that takes into account the physical state in which PAHs occur. Here, solvent extraction is proposed as such a characterisation test. Solvent extraction experiments were performed with a 1/1 acetone-water mixture on (particle size fractions of) PAH-contaminated harbour sludge. The PAHs were more easily dissolved from fine than from coarse fractions, which indicates that the PAHs in the fine fractions are better (bio)available. The results further suggest that PAHs were present in particulate form, absorbed in organic matter and dissolved in oil. The performed extraction experiments provide a basis for further development of existing models.     

Microbial source tracking to identify fecal sources contaminating the Toronto Harbour and Don River watershed in wet and dry weather

Identification of sources of fecal pollution in urban areas is critical for protecting public health, the environment, and guiding remediation. We collected 670 water samples at 46 sites in 2018 to study fecal pollution in the Toronto Harbour and Don River watershed. Water samples were analyzed for E. coli, wastewater chemicals, and microbial source tracking DNA markers using a digital PCR technique. Microbial DNA markers were useful for interpreting the sources of elevated E. coli concentrations in the study. The HF183 marker for human sewage was the most frequently detected DNA marker, occurring in 100% of samples taken from the Don River and associated outfalls. It was also frequently detected in the Inner Harbour and outfalls along the Toronto harbour front. It was detected less frequently and at lower levels in the outer harbour. Detection of a human mitochondrial DNA marker and wastewater chemical markers such as caffeine provided additional evidence of widespread sewage contamination. The gull DNA marker was widely detected, but at lower frequencies and levels than human source DNA markers. A wet weather response of increased E. coli and human DNA marker concentrations occurred at most sites. However, human DNA markers were also widely detected on dry weather sampling days, indicating sewage cross-connections in stormwater and dry weather CSO systems. The cumulative impact of cross-connected stormwater outfalls is likely an under-recognized source of sewage contamination. E. coli and HF183 DNA marker levels observed can serve as benchmarks for evaluating future water quality improvements from wastewater infrastructure investments.     

多氯联苯在土壤水环境中生物降解过程规律研究

土壤水环境中的有机污染物多氯联苯(PCB)可以采用土地生物处理的方法进行降解，在综合考虑土壤水环境系统中有机污染物生物降解各分过程的基础上所建立的数学模型，可以预测降解PCB所需的时间、降解程度以及降解结束后被土壤所屏蔽的PCB的量。数学模型通过美国Alcoa公司在LTU基地的大型土地生物处理工程得到了验证。利用数学模型和理论分析，预测了2，3，4和5-Cl-PCB的土地生物处理过程及规律。     

Spatial and temporal variations of niphargus populations in interstitial aquatic habitat at the karst/floodplain interface

Artificial substrates buried in stream sediments at the karst/floodplain interface were used to examine the spatial and temporal variations of Niphargus populations. The study was carried out at two stations in two different areas of the French Jura. One was mainly supplied by karst water (Verna station), the other by both karst and surface waters (Pissoir station). The occupation of interstitial habitat was found to depend on several interacting factors:

• 1 The waterflow and its changes at the outlet. The correlation between abundance of individuals and discharge was strongest with the discharges two to four days before sampling. The structure and restoration of populations after a spate related to geological characteristics. In particular, restoration was slower and more difficult in the sediments located at the base-level of a massif (Verna) than at an overflow level (Pissoir).
• 2 The location of the sediments. At the Pissoir station, the number of individuals was higher at the main outflow, but also for both stations, on the banks opposite the outlet. Animals drifting from the karst system found refuge in the sediment of the opposite bank. Almost no Niphargus were found upstream from the outlets. At the Verna station, Niphargus were only found inside the cave.
• 3 The variability of the number of animals at different depths in the sediment was more difficult to explain. At the station mainly supplied by karst water, which presented a relatively constant flow during the study, the distribution seemed to be random. At the other station, where discharge varied considerably, the vertical distribution globally presented a gradient in abundance with more individuals in the upper sediment level. This gradient varied according to the samples. Discharge changes partly explained these results.

     

Strategies for management of contaminated sediments within the meuse river-system

The sediments in the Meuse valley are contaminated on a large scale by diffuse sources. The project ‘Maaswerken’ aims at the enlargement of the discharge capacity of the river Meuse. In the realization of the project, a full-scale clean-up operation would not be realistic and not effective because of recontamination and the enormous scale and costs involved. The concept of dynamic soil management offers a solution to this problem. This approach to remediation implies putting back contaminated sediments of indigenous quality within the river system. Preconditions are determined by risk assessment and local conditions. The first aim is improvement of the environmental quality of the river system. Other objectives such as the development of natural areas, the mitigation of geohydrological effects and the exploitation of sand and gravel can be realized by several forms of beneficial use of contaminated sediments. Dynamic soil management is expected to be a pragmatic and cost-effective solution for the problem of contaminated sediments.