Contaminated Land Remediation in the UK with Reference to Risk Assessment: Two Case Studies

The approach to land reclamation in the UK has traditionally relied upon the use of cover and concealment, which can leave a legacy of problems below the ground. Alternatively, the bulk export of materials to licensed landfill has often been used, but this (a) simply transfers a problem, (b) can cause considerable disruption, and (c) is becoming increasingly expensive. Remedial strategies involving the use of barrier systems or off-site removal both have their place in the efficient and economic development of contaminated sites. However, there is now increasing interest in the use of on-site technology which can provide cost savings and by treating, destroying or stabilizing contamination, can serve to minimize future liabilities. The design, costing and application of treatment, as opposed to cover or disposal, depends fundamentally on understanding the problem and evaluating the capabilities and availability of appropriate technologies. With reference to UK case studies, this paper highlights some of the options available and routes taken in order to achieve site-specific, commercially-acceptable, remedial responses.     

Environmental Dredging on the Birmingham Canals: Water Quality and Sediment Treatment

Sediments in sections of the central Birmingham canals are heavily contaminated with heavy metals and mineral oils. The sediments promote high levels of metals within the water column, which suppress the establishment of aquatic vegetation and fisheries. Sediment disturbance by boat traffic results in the release of mineral oils which cause unsightly surface oil sheens.
Studies into a variety of treatment methods indicated that removal and ex-situ treatment of the contaminated sediments would significantly improve water quality and result in environmental benefits.
Funding from Birmingham City Council and British Waterways enabled the award of a contract with a value of approximately £800000 and commencement in February 1993 for the removal and processing of about 24 000 m³ of sediments by soil washing prior to off-site disposal. The nature of the sediments and water are reviewed, and the results of the soils washings are discussed. The impact of the dredging operations on water quality was monitored during the works and generally observed to be localized. An environmental management plan is now being implemented and the objectives for this are discussed.     

Impact of process design on greenhouse gas (GHG) generation by wastewater treatment plants

The overall on-site and off-site greenhouse gas emissions by wastewater treatment plants (WWTPs) of food processing industry were estimated by using an elaborate mathematical model. Three different types of treatment processes including aerobic, anaerobic and hybrid anaerobic/aerobic processes were examined in this study. The overall on-site emissions were 1952, 1992, and 2435 kg CO₂e/d while the off-site emissions were 1313, 4631, and 5205 kg CO₂e/d for the aerobic, anaerobic and hybrid treatment systems, respectively, when treating a wastewater at 2000 kg BOD/d. The on-site biological processes made the highest contribution to GHG emissions in the aerobic treatment system while the highest emissions in anaerobic and hybrid treatment systems were obtained by off-site GHG emissions, mainly due to on-site material usage. Biogas recovery and reuse as fuel cover the total energy needs of the treatment plants for aeration, heating and electricity for all three types of operations, and considerably reduce GHG emissions by 512, 673, and 988 kg CO₂e/d from a total of 3265, 6625, and 7640 kg CO₂e/d for aerobic, anaerobic, and hybrid treatment systems, respectively. Considering the off-site GHG emissions, aerobic treatment is the least GHG producing type of treatment contrary to what has been reported in the literature.     

Contaminated Land Remediation: Economics v Liability

Chemical investigations of contaminated land can be expensive and yet still leave the landowner unaware of his/her full environmental liability. An approach to an effective means of planning chemical investigations is described by a case study of a contaminated site near London. This approach limits environmental liability in a cost-effective manner.
One of the main problems encountered in assessing the degree of contamination of land for the purposes of technical design, and ultimately for developer confidence, is the lack of recognized UK standards for acceptable levels of contaminants.
Using a second case study relating to a large contaminated site in the Midlands, the paper describes how a set of site-specific standards, for soil and water, was derived and used to develop a reclamation strategy for an 81-ha site. The case study also demonstrates the approach which was adopted in handling a large amount of analytical data and other quantitive information needed to produce a set of 'constraint models'. From these constraint models, the strategy for reclaiming the site has been developed.     

Identifying Land Contaminated by Chlorinated Hydrocarbon Solvents

This paper provides a method of identifying land contaminated with chlorinated hydrocarbon solvents by sampling and analysing soil gas. Relationships are presented which enable levels of soil gas contamination to be related to levels of soil and groundwater pollution. Two case studies are presented. Soil gas surveying of an industrial site with severe groundwater pollution demonstrated that standards for contaminated land are insufficient to protect groundwater. Solvent levels in groundwater were one to two orders of magnitude higher than UK permitted concentrations in drinking water, whereas soil contamination values did not reach polluted levels. Surveying of a site occupied by a disused fire station showed significant differences in patterns of soil gas and groundwater pollution. This is explained by direct pollution of groundwater though the well at the site and/or possible flow of polluted groundwater to the site from adjacent areas.     

棕地景观规划设计中的土壤修复方法——以首钢二通机械厂改造景观规划设计为例

棕地改造受到国内外人士越来越多的关注和重视,对于棕地改造而言,土地污染是改造、开发再利用首要解决的问题,在首钢二通机械厂改造项目中,尝试将土壤修复与景观规划相结合,采用最佳修复方法,在土壤修复的同时具有一定的景观性。     

Long‐term phosphorus accumulation and removal efficiency in a land‐based wastewater treatment system in the UK

The study aims to assess the long‐term phosphorus (P) removal in a land treatment system (LTS) in the UK. Different sections of the site have been irrigated with wastewater effluent for different periods of time for up to 85 years. The amounts of P discharged and accumulated were calculated from historical data, estimations of water consumption, composition and soil measurement. The total P input during the study period was estimated to be 90 010 kg, the average P removal was 4% and there was no significant difference in the total P accumulated between plots irrigated for different periods, indicating that the sorption capacity of the soil might be saturated. Despite the low P retention rates in the LTS, there is no evidence that emissions from this system are affecting P concentrations in either the nearby river or the local chalk aquifer. Gaps remain, however, in performance optimisation and longevity forecasting.     

Waste Stabilization Ponds: A Viable Alternative for Small Community Treatment Systems

Waste stabilization ponds are widely used in many European countries, such as France and Germany, for the treatment of wastewater from mainly small communities. There would seem to be no reason why they should not also be a suitable treatment process for populations of under 2000 in the UK. The relative advantages and disadvantages of ponds are compared to other small community treatment systems, such as rotary biological contactors, biological filters and reed-bed systems, particularly in relation to effluent standards with respect to algae, nutrient removal and relative costs.     

Current Developments in Contaminated Land Treatment Technology in the UK

This paper reviews recent developments in contaminated land treatment (soil and groundwater) in the UK, particularly with regard to:

• (i) 

  The combination/integration of individual soil-treatment unit processes and the use of 'extensive' technologies;
• (ii) 

  UK demonstration and emerging projects including those in the NATO/CCMS (Committee for Challenges to Modern Society) Pilot Study on Research, Development and Evaluation of Remedial Action Technologies for Contaminated Soil and Groundwater; and
• (iii) 

  Contaminated land treatment technology research and development in the UK.

     

Oil-contaminated soils under engineering constructions and technology of soil remediation

Oil around buildings is sucked under them. The conditions for accumulation of oil exist under engineering constructions. It is necessary to clean oil-contaminated territory, whether it is free from infrastructure or under engineering constructions. Cleaning technology with hydrocarbon-reducing micro-organisms was tested on the site of a tank farm with contaminated soils. The sorbent with micro-organisms placed at a depth of 40–60?cm below the technical buildings has cleaned the oil from the soil. The micro-organisms assimilate the n-alkanes with C₁₄ chains rather than the C₃₂–C₄₀. The oil is destroyed quicker under the constructions than in the open areas.     

The relative influence of distant and local (DEW-line) PCB sources in the Canadian Arctic

Soil PCB contamination has been delineated at 18 of 21 Distant Early Warning Line (DEW-line) stations being cleaned up by the Canadian Department of National Defence (DND). As a result, detailed surface soil delineation data has been reported for contamination exceeding 1 microg/g (dw total Aroclor), which is the remedial criteria for PCB contaminated soil under the DEW-line cleanup project. The results of this delineation work has allowed us to estimate the mass of PCB contained in surface soil at these sites and to quantify the DEW-line as a source of PCBs to both local and Arctic wide contamination. Our analysis of DEW-line cleanup delineation reports suggests that pre-cleanup surface soils (top 10 cm) with over 1 microg/g PCB constituted a source of PCBs that ranged from 0.8 to 43 kg with a mean of 18 kg. The total mass of PCB at all 18 sites was 119 kg. Previous studies have described a "halo-effect" that surrounds DEW-line sites, whereby PCB signatures in soil and plants up to 10 km from source areas were attributed to the local source. At Cambridge Bay (CAM-M), Nunavut, our inventory of PCB sources and redistribution suggests that up to 3.4 kg of PCB were exported from the site to the surrounding tundra prior to cleanup. The primary mechanism of transportation appears to be wind borne particulate. Potential vapour phase emissions of PCB from contaminated soil at DEW-line sites appears to have been negligible.     

Biological Nutrient Removal: Design Snags, Operational Problems and Costs

The EC urban waste water treatment Directive will lead to some sewage-treatment works in the UK having to remove nitrogen and phosphorus. The paper reviews the basic biological processes which are available for retrofitting existing activated-sludge plants to achieve this removal, and then points to some of the problems which are encountered with these processes in other countries. The authors make suggestions as to how these problems can be overcome in design and operation. The paper also provides a cost comparison of different ways of uprating an existing nitrifying activated-sludge plant to achieve nitrification/ denitrification and phosphorus removal.     

Laboratory-Scale Investigations of Algal Toxin Removal by Water Treatment

The paper describes some water-treatment processes which have been investigated on a laboratory and pilot-plant scale for their effectiveness in removing toxic algal cells and the dissolved toxins microcystin-LR and anatoxin-a. Oxidation with ozone or potassium permanganate, or treatment by biological activated carbon, were found to be the most effective processes for removal of the dissolved toxins. Chlorination was effective only for the removal of microcystin-LR. Toxins, contained within algal cells, could be removed effectively by coagulation, clarification and filtration under suitable conditions. Consideration of the structure and properties of micro-cystin variants suggests that treatments which are suitable for removal of microcystin-LR and anatoxin-a should be suitable for removal of other microcystins.     

Some experimental results of laser beam interaction with surface layer of brick

Preservation of cultural heritage is gaining increasing attention all over the world. Restoration of ancient artwork and architecture requires even more effective cleaning techniques than are currently available. Laser cleaning appears to be a suitable method for removing surface contaminants from porous materials like masonry. This paper presents some effects of laser beam interaction (ruby laser, free generation regime) with clean and contaminated surface of brick which was subjected to long term exposure to atmospheric conditions. The effects of the laser beam interaction have been examined by the optical microscopy method, scanning electron microscopy and X-ray microanalysis. The present research revealed the potential application of laser irradiation for cleaning of the surface layer from contaminants and possible modification of the chemical composition of cleaned surfaces.     

Process selection for sanitation systems and wastewater treatment in refugee camps during disaster-relief situations

Disasters and emergency situations can disrupt the provision of clean water and hygienic sanitation, which are crucial for maintaining public health. Excreta disposal in emergencies has often been a low priority and this has led to the provision of unsuitable on‐site sanitation systems in urban areas. A decision algorithm for the selection of adequate excreta‐disposal solutions suitable for different disaster‐relief scenarios is presented. The special requirements of a wastewater treatment system for deployment during an emergency are discussed and a semi‐centralised system is recommended to serve 5000 refugees under a range of assumed loading conditions. Twenty‐three aerobic, anaerobic and natural systems are considered for secondary treatment and a process‐selection matrix is presented based around 16 evaluation criteria. A system layout is developed based around several sanitation facilities including sedimentation tanks connected to a centralised roughing trickling filter and an activated sludge unit, which provides optimal performance against the evaluation criteria. The system provides the required treatment performance in an easy‐to‐deploy, low‐cost compact installation.     

南宁地王国际商会中心基础设计

结合南宁地王国际商会中心工程的地质特点,介绍了在满足复合地基承载力和变形要求前提下合理布置桩筏联合基础的做法及其设计步骤。布置桩筏联合基础时使桩筏分别落在不同土层上,以充分利用不同深度地基土的承载力,最大限度利用桩身强度和天然地基承载力。该做法可以取得很好的经济效益,可供工程设计人员参考。     

我国饮用水中内分泌干扰物的去除研究进展

对我国水源水中内分泌干扰物（EDCs）的存在现状以及采用常规饮用水处理工艺、深度处理工艺和高级氧化技术去除EDCs的研究现状和进展进行了综述。我国水源水已受到EDCs的严重污染，其中主要包括农药类、壬基酚、双酚A、邻苯二甲酸酯类以及多氯联苯类等；常规饮用水处理工艺对EDCs的去除非常有限；饮用水深度处理工艺可降解一定的EDCs；生物处理技术具有成本低、可去除多种EDCs的特点，具有很好的应用前景。     

New Treatment Processes for Pesticides and Chlorinated Organics Control in Drinking Water

Sources of pesticides and chlorinated organic compounds potentially found in water sources are reviewed. International and UK drinking water standards for these compounds are discussed and compared with concentrations found in ground and surface waters derived from lowland agricultural and urban areas.
Water soluble herbicides including triazines, phenylamides (urons) and chlorophenoxy acids are the most commonly reported types of pesticide compounds found above 0.1 μg/l in water sources. The more toxic, and less water soluble, organo-chlorine and organophosphorus pesticides are rarely reported.
Chlorinated organic solvents are reported as contaminants of some groundwaters. Disinfection by-products, in particular trihalomethanes, formed during the chlorination of waters containing natural organics, are widely reported, sometimes at concentrations above current UK standards.
The effects of conventional water-treatment processes on the concentrations of these organic compounds are discussed. Additional water-treatment processes, designed specifically for trace organic micropollutant removal, are identified and reviewed. Ozonation, activated-carbon adsorption and air stripping are acknowledged as appropriate advanced water-treatment process solutions. Developments in novel technologies include organics destruction via advanced oxidation processes, biological processes, membrane technology and novel adsorbents.
Thames Water Plc is contributing to research in this area, investing over £5 million in pilot- and large-scale trials prior to a £200-£300 million capital investment programme in advanced water treatment in the 1990s.     

Biological Processes at Saints Hill Water-Treatment Plant, Kent

The new treatment plant at Saint's Hill has been operating since May 1992 and biologically treats ground-water to remove iron, ammonium/ammonia and manganese. The paper describes the project, the processes involved, the significance of pilot-plant studies, the different stages of commissioning and plant efficiency.
This method of treatment, although new to the UK, is well-established in France, and reference to existing plants using the processes is made for purposes of indicating the range of applicability of biological treatment processes.
Specific conditions are required for biological processes. Not all raw waters can be economically treated to produce an environment which is appropriate for bacterial activity. Conditions for biological iron and manganese removal are different. The paper illustrates the importance of pilot studies to establish the feasibility of biological processes and to determine the design parameters for industrial-scale works.     

The Root-Zone Process at Holtby Sewage-Treatment Works

THE 'root-zone' sewage-treatment proccess was introduced to the UK and Yorkshire Water in 1984, with claims that capital and operating costs were significantly less than for conventional processes. The design and construction of the experimental root-zone bed at Holtby (which forms part of Yorkshire Water's contribution to the evaluation of the process in the UK), is described. The planting of the Phragmites , their growth and the performance of the bed are discussed. Suspended solids and BOD removal efficiencies have satisfied the predictions of the designers for the performance of a bed which is still immature, although ammonia and phosphate removals have been low. The role which is played by the reeds is considered to be minor, and it is suggested that it is too early to judge the Holtby bed either a success or a failure. The paper also discusses the problem of weed control, the importance of floor slope, maturity of the system and the use of gravel instead of soil.