Advisory Council on the Environment

Advisory Council on the Environment - Report of the Study Visit to Europe 6 - 16 August 2001

(ACE Paper 51/2001)
For discussion

Table of Contents
1. Executive Summary
2. Introduction
3. Programme in London and Liverpool, the United Kingdom Plant
3.1 Briefings by the UK Joint Environmental Units
3.2 Visit to Crossness Sewage Treatment Plant in London
3.3 Visit to United Utilities' Liverpool Waste Water Treatment Works at Sandon Dock
3.4 Briefing by Environment Agency North West Region (EANWR)
3.5 Visit to United Utlities' Davyhulme Waste Water Treatment
4. Programme in Oslo, Norway
4.1 Visit to VEAS Waste Water Treatment Plant
4.2 Visit to Klemetsrud Incineration Plant (KIP)
4.3 Briefing by Norwegian Ministry of Environment and Pollution Control Authority
5. Programme in Paris, France
5.1 Visit to Cergy-Pontoise Waste Water Treatment Plant (CPWWTP)
5.2 Visit to Acheres Wastewater Treatment Plant
5.3 Visit to Colombes Waste Water Treatment Plant
5.4 Visit to Azalys Waste to Energy Plant (AWEP)
6. Programme in Hague, the Netherlands
6.1 Meeting with Dutch Ministry of Housing, Spatial Planning the Environment
7. Observations
8. Conclusions
9. Acknowledgements
Appendix I - Membership of the delegation MSWORD
Appendix II - Itinerary for the visit MSWORD
Appendix III - List of reference materials acquired MSWORD
Appendix IV - Comparison table on the plants visited


1.1 The Advisory Council on the Environment (ACE) delegation comprising 10 ACE members and two government officials conducted a study visit to UK, Norway, France and Holland from 7 August 2001 to 15 August 2001 to learn their experience in environmental protection with particular attention on the use of the Biological Aeration Filter (BAF) technology in wastewater treatment. Led by Mr. Peter Wong, the Chairman of ACE, the delegation visited seven wastewater treatment plants, two incinerators and held discussions with four European environmental authorities.

1.2 BAF is adopted in many of the wastewater treatment plants visited. Although difficulties (e.g. loss of filter media, blockage of pumps, damage of nozzles and emission of odour) were encountered by some of the plants during the early stage of implementing BAF, these difficulties could be overcome by subsequent design rectification and BAF was regarded by them as a correct choice. It appears that the experience of these forerunners could contribute significantly to the design of future BAF plants.

1.3 Incineration is accepted in Europe as an appropriate waste treatment method. An issue requiring attention is possible resistance from residents near new planned incinerators. One observed approach in overcoming resistance is to have early and proactive interactions with residents and make the process very transparent so as to allay any unwarranted fears. Incentives such as community improvement programmes are found to be useful. Efforts are made to make incinerating plants aesthetically pleasing in order to win public acceptance. In fact, aesthetically pleasant architectural design was also a key feature observed in several of the wastewater treatment plants visited.

1.4 Sustainable development received very high-level support from the UK Government. Environmental impact assessment is given great attention in the Netherlands not only in the context of development projects but also in selective major Government policies in the form of an E-test. The Dutch government is still refining its EIA process.

1.3 The use of the "Design-Build-Finance-Operate-Transfer" approach in developing sewage treatment as well as incineration facilities in overseas countries proves to be very successful. It allows greater flexibility in adjustment of process and ensures optimal cost-effectiveness.


2.1 The quality of inland and coastal waters in Hong Kong has all along been the subject of major concern of the Advisory Council on the Environment (ACE). In November 2000, the International Review Panel (IRP) issued its report on the Review of Strategic Sewage Disposal Scheme. One of the recommendations of the report is to incorporate tertiary sewage treatment facilities at the Stonecutters Island Sewage Treatment Works by using Biological Aerated Filters (BAF) technology. The IRP also suggested that sewage having received treatment up to tertiary standard could be discharged directly into the Harbour instead of through the originally proposed long oceanic outfall to the south of Lamma Island.

2.2 After examining IRP's recommendations, the Government announced in March 2001 that it would consider moving directly to tertiary treatment for the harbour area sewage and would carry out the necessary environmental studies and trials of BAF and other viable compact tertiary treatment technologies to confirm whether discharge into the harbour waters will be environmentally acceptable and what type of system would be most practicable and cost effective. In view of the IRP report and the plan of the Government, ACE, decided to conduct a study visit to Europe to learn from their experience in wastewater treatment, particularly regarding the use of the BAF technology. The main focus was to visit major wastewater treatment facilities in London, Manchester, Paris and Oslo where wastewater treatment technologies in the context of increasing demand and space constraints should be applicable to Hong Kong.

2.3 Having regard to the forthcoming environmental issues that might be brought to the ACE for advice, it also took the opportunity to visit sludge incinerators in London, Manchester, Paris and Oslo and to study the system of environmental impact assessment in Amsterdam.

2.4 The delegation comprising 10 ACE members and two Government officials is led by Mr. Peter Wong, the Chairman of ACE. The membership of the delegation is at Appendix I.


3.1 Briefing by the UK's Joint Environmental Markets Unit (JEMU)

Role of JEMU

3.1.1 JEMU is a national Government unit responsible for promoting and supporting the UK environmental industry. It is jointly formed by the Department of the Environment, Food and Rural Affairs and the Department of Trade and Industry. The unit is tasked to nurture the development of a strong and competitive environmental industry. According to OECD's projections, the annual business turnover of the global environmental industry was roughly US$600 billion in 2000 and will increase to some US$1,700 billion by 2010. JEMU aims to increase the UK's market share of the global environmental industry from below 5% at present in a progressive manner. More information about the JEMU can be found at http://www.dti.gov.uk/jemu.

UK Government's sustainable development policies

3.1.2 Sustainable development has been accorded very high level of support within the UK Government. There is independent Sustainable Development Council which reports to the Prime Minister directly. The UK Government believes that this, coupled with joint efforts across ministries and departments, is essential to orchestrate policy and mindset changes within the Government. So far, the UK Government has formulated ten principles and developed 150 core indicators under 15 broad headline indicators to measure their performance in terms of sustainable development. Of the 15 headline indicators, six of them are related to the environment, another six on social factors and the remaining three on economic factors. These 15 headline indicators are important as the UK Government will set or adjust its policies based on changes of these indicators. The UK experience indicates that public education programmes are very important means to secure public support for sustainable development. In respect of reducing greenhouse gases emission and preventing global climate change, the UK Government believes that their nation is well on its way to meet its obligations under the Kyoto Protocol.

Wastewater treatment issues in the UK

3.1.3 In the UK, increasingly more private water service companies are responsible for the supply of potable water to customers and for the collection and treatment of sewage generated by them. These companies will need to expand or upgrade their systems to cope with the growing demand and to follow the new directives given by the regulatory bodies (the Environmental Agency on effluent and environmental standards, and the Office of the Water Services on business and financial matters). In return, they charge their customers for the services provided and the investments made, subject to monitoring by the regulatory bodies. At present, there are 25 water services companies providing potable water. Ten of them are also involved in the collection and treatment of sewage. On average, a UK household pays about £0.7 (HK$8.05, assuming exchange rate £1=HK$11.5) per day for water and sewage charges altogether. The UK Government is committed to implementing the following EU Urban Waste Water Treatment Directives -

By 1998 Provision of secondary treatment for discharges from all major cities
By 2000 Provision of secondary treatment for discharges from agglomerations exceeding 15,000 people (not achieved yet)
By 2005 Provision of secondary treatment for all significant discharges from agglomerations exceeding 2,000 people.

It is estimated that the UK will spend more than £10 billion (HK$115 billion) on new sewage treatment facilities between now and 2005.

Other environmental issues

3.1.4 Sir Crispin Tickell, Chairman of the UK Sustainable Development Council joined the briefing as a guest speaker and exchanged views with the delegation. Sir Crispin was very positive about the Mainland's commitment to environmental protection. He was also very impressed by the pragmatic approach adopted to deal with various environment issues. On the other hand, he criticized the US Government for its irresponsible attitude on many important environmental issues, such as its recent retraction from the Kyoto Protocol. Sir Crispin was supportive of the use of environmental taxes to create economic incentives for environmental protection. He also suggested that each region should pursue development strategies based on local circumstances.

3.2 Visit to Crossness Sewage Treatment Plant in London

Comparison of various compact sewage treatment technologies

3.2.1 Thames Water, which operates the Crossness Sewage Treatment Plant and is now owned by the German company RWE of Essen, runs some 380 wastewater treatment plants across the UK. A comparison of the Biological Aerated Filter (BAF) technology vis-ˆj-vis other sewage treatment technologies provided by Thames Water based on its own experience is summarized in the table below -

Type of sewage treatment technology Footprint Saline Capital expenditure
(excluding land cost)
Operating expenditure
Biological Aerated Filter 1 Y 1 1
Trickling Filter 5 Y 0.7 0.7
Activated Sludge 2.5 Y 0.8 0.9
Deep-shaft Activated Sludge 1.5 Y 0.9 0.9
Sequential Batch Reactor 2 Y 0.9 0.9
Submerged Membrane Bio-Reactor 0.9 Y 1.5 1.1
Note: All comparisons are made with reference to BAF. For instance, 5 in footprint means five times the footprint required under BAF.

Thames Water has developed the SAFE process which is a downflow BAF system using sunken filter media. The filter media is typically 3 to 6 mm in size with a specific gravity of 1.5 to 1.7. This form of BAF system is similar to some of the French system (e.g. the one from Degremont).

Main features of Crossness STP

3.2.2 The Crossness STP is located on the south bank of the River Thames and serves a population of about 1.6 million in the area. It was one of the earlier plants which treats the main sewage channels from South London and as a result utilizes a very large landtake. The average daily flow of sewage processed by the plant is about 600,000 m3. The treatment process mainly comprises preliminary screening, grit removal, primary settling and secondary treatment by the activated sludge process using surface aeration. The sewage sludge is digested in the primary digestion tanks before displacing into the open secondary digestion tanks for storage prior to incineration. Gas produced by the sludge digestion plant is used to generate electrical power for the use of the plant.

3.2.3 Incineration has been used to handle the sludge produced at Crossness STP almost since the disposal of sewage sludge to sea was banned. Sludge incineration takes place in a fluidized bed incinerator to allow complete combustion of the sewage sludge. Flue gas leaving the waste heat boiler is dedusted using bag filter and scrubbed to remove pollutants such as dioxin and mercury. The electrical power generated from incineration is then ploughed back into the incineration process. The inert ash produced is sent to landfill. The Crossness STP handles some 35,700 tonnes of sludge by incineration annually and produces some 55 GWh of electricity. The ash produced amounts to 5,000 tonnes annually. The actual Dioxin emission is 0.05 ng/m3 which is well below the regulatory requirement of 0.1 ng/m3.

3.2.4 It was claimed that Thames Water has the lowest charges in Europe. However, it is subsequently found out that the Environmental Agency for England and Wales rated Thames Water its top polluter.

3.3 Visit to United Utilities' Liverpool Waste Water Treatment Works at Sandon Dock

Main features of Liverpool WWTW

3.3.1 The Liverpool WWTW is owned by the United Utilities. The plant sits on the dockside of Liverpool and serves a population equivalent of 950,000. It is perceived that such waterfront land is of value and care has been taken to minimize the landtake for the operations. It is the key project to arrest the serious pollution at the Mersey Estuary which used to be one of the dirtiest rivers in Europe. At present, coarsely screened wastewater is channeled to the plant by a 28 km interceptor sewer and is then lifted from the interceptor sewer by 8 centrifugal pumps. The treatment process includes the usual preliminary screening, grit removal, primary settlement and the flow is then split and raised by screw pumps to the 20-cell Degremont Biofor Biologically Aerated Flooded Filter (BAFF) plant for removal of 70% of BOD and 75% of COD. The plant is designed to achieve only carbonaceous BOD removal (i.e. no requirement for nitrification nor de-nitrification) and is the largest operating plant of its type in the world. The BAFF plant costing £70M (HK$805M) commenced operation in January 2000. The plant occupies an area of 22 acres (8.9 hectares). The sludge from the plant is digested anaerobically and is transferred to a regional treatment facility for reuse or incineration. It is worth to note that there is only a relatively small portion of sludge from the BAFF process compared to that from the primary settlement process (40 tonnes dried solids of primary sludge compared with 5 tonnes dried solids of BAFF sludge) possibly because the BAFF is designed to achieve only carbonaceous BOD removal.

Salient problems encountered

3.3.2 During commissioning, the plant experienced a number of problems. A major problem is the loss of filter media for the BAFF process. The loss amounted to 8 tonnes per day at one stage and blocked the pumps eventually. After adjustment was made to the backwash process, the media loss has been reduced to 0.5 tonnes per day. Another problem arose when the highly active biomass from the BAFF backwash was returned to the primary settlement tanks. Because of the long retention time in these tanks, the active biomass consumed all the oxygen and caused anaerobic condition and created odour. The odour problem has been substantially resolved after the media loss was under control.

3.3.3 The lessons learned were :

  • It is all very well to have pilot trials, but the real mechanical problems will only show up in the real plant.
  • BAF generates biomass that is still very active. Relevant parts of the plant must be covered to avoid possible odour problem.
  • Need to control / manage industrial discharges as they may cause major fluctuations.
  • BAF is sensitive to chloride fluctuations which happened mostly during storm conditions.
  • If backwash goes into conventional primary tanks with long retention time, it will cause septicity and odour.

3.4 Briefing by Environment Agency North West Region (EANWR)

3.4.1 The Agency is responsible for protecting and enhancing the environment in the North West Region which covers the city of Warrington . It regulates industry and inspects industrial sites to protect the environment and people from pollution and environmental risks to health; maintains essential flood defences, water resources and river navigation structures; restores and improves the land and wildlife habitats; monitors and assesses the environment; and collects and disseminates environmental data and information. The NW Region has a population of approximately 7 million. It owns 25% of the derelict land in the UK and has a coast line of 765 miles with 37 bathing waters. The Region also accounts for 13% of the national waste produced at present. So far, the EANWR has issued more than 1,000 waste management licences and 6,500 discharge consents. More about the role and functions of an Environmental Agency can be found at www.environment-agency.gov.uk.

3.4.2 Although they are the regulators for the region, they see themselves more as educators and influencer of minds.

3.5 Visit to United Utilities' Davyhulme Waste Water Treatment Plant in Manchester

3.5.1 Davyhulme WWTP is United Utilities' largest wastewater treatment plant which provides sewage treatment for a population equivalent in excess of 1.2 million. The plant treats a mixture of industrial wastewater, domestic sewage, and surface run-off for a large proportion of Manchester. The treatment includes screening, grit removal, primary settlement, a secondary treatment process by two fully enclosed surface aeration activated sludge streams, and finally a tertiary treatment process (for nitrification) by a BAFF plant, which is the largest operation plant of its kind in the world. Sludge is digested and then thickened using polyelectrolyte dosing and gravity belt thickeners, before being pumped to regional sludge reprocessing plant for further action.

3.5.2 Unlike the situation in Sandon Dock, Liverpool, the Davyhulme has no shortage of land. United Utilities has chosen BAFF as its tertiary treatment process based mainly on cost considerations. It was claimed that the total life cycle cost (i.e. capital plus operating cost) is more favourable compared with other processes.

3.5.3 There were discussions on whether centralized treatment plants pose unacceptable risks. United Utilities' view is that since treatment processes are built in multiple parallel modules, the risk of total failure is small. Their experience shows that the "four modules arrangement" provides the best operational flexibility without compromising cost-effectiveness.

3.5.4 The managers of this site seem to be very cost conscious and "sweat the assets" to get the best out of them.

3.5.5 When dealing with industrial discharges, they feel that a large plant has the capacity to absorb shocks that could swamp a smaller plant. They base their risk model on four streams, any one of which can be taken out and still maintain quality of discharge.


4.1 Visit to VEAS Wastewater Treatment Plan in Oslo

Main features of VEAS WWTP

4.1.1 This VEAS WWTP was built by the City of Oslo in 1985 in a rock cavern and is completely hidden from the outside except the sludge digester and gas holding tank. Sewage is conveyed to the plant via a 42 Km long tunnel system. The treatment plant is a two-stage Degremont Biofor Nitrification and Denitrification plant. The CEPT process with lamella settling that precede the BAF process is designed for maximum BOD and SS removal in order to have optimum nitrification in the first stage BAF. The second stage BAF provides denitrification only with the addition of methanol. For the CEPT process, a special polymer, PAX, is applied to prevent excessive precipitation of phosphorus, which is needed as a nutrient in the BAFs. Sludge is anaerobically digested and then treated by vacuum drying. The dried sludge (which can be up to 55% dried solid content) is then used for agriculture. The plant treats between 260,000 to 330,000 m3/d of flow.

4.1.2 Because the plant is designed to achieve high level of nitrogen removal (70% removal of Total N and 85% removal of TKN), the required level of treatment cannot be achieved by a single stage BAF system. Separate second stage denitrifying BAF cells were required. The area requirement has thus substantially increased.

Salient problems encountered

4.1.3 The plant introduced the BAF process as early as 1992 when the technology was still in its infancy . Compactness was the main consideration when the BAF process was selected at that time. Throughout the implementation stage and the initial commissioning period, a lot of technical problems such as the choice of media, the design of backwash process were encountered and they were all resolved in-house with research support from local universities. At one stage, the plant also encountered significant media loss of up to 3% in the BAF process but the problem was resolved by a redesign of the backwash process.

4.1.4 The plant tried to minimize use of chemicals and hence minimize the production of sludge. It also tried to avoid mechanical means and used air for flocculation to run smoothly. Up to 2-3% of seawater is added to the wastewater to help with phosphorus removal.

4.2 Visit to Klemetsrud Incineration Plant (KIP)

Waste Management in Oslo

4.2.1 In Oslo, both waste collection and disposal are run by the private sector. There are two incineration plants and one landfill there at present. The two incineration plants can handle 250,000 tonnes of waste annually. The landfill is not allowed to accept any organic and chemical waste. The landfill in Oslo is scheduled to be closed down in 2007. However, although the Norwegian people generally accept that incineration is the ultimate means for waste disposal, a lot of persuasion and explanation is still required to convince the public when new incineration facilities are planned. Moreover, in response to strong public concern over Dioxin emission, the emission standard for the incineration process has been tightened over the years. At present, Dioxin emission is not allowed to exceed 0.05 ng/m3 for new incinerators.

Main features of KIP

4.2.2 The plant is the largest in Norway and is able to handle 150,000 tonnes of waste annually. It was built in the 1960's and upgraded in 1985. Waste is incinerated at a temperature of 950℃. The exhaust gas is treated by electrostatic precipitator, chemical scrubber and bag filter before discharge to the atmosphere. The dioxin standard for this plant was set at 0.2 ng/m3. Its handling capacity is planned to increase to some 320,000 tonnes in the coming six to seven years. At present, it costs 700 NOK per tonne to handle waste at KIP and each tonne of waste can generate power of 2.5 MW/hr.

4.2.3 The incineration plant is designed to handle chemical waste as well, but the management believed that it would be cheaper to send the chemical wastes to another country such as Denmark to handle as there are no restrictions on such transfers.

4.3 Briefing by Norwegian Ministry of Environment and Pollution Control Authority

Ministry of Environment

4.3.1 The Ministry comprises six directorates as follows -

  • Pollution Control Directorate supported by Norwegian Pollution Control Authority;
  • International Cooperation Directorate supported by Norwegian Polar Research Institution;
  • Nature Management Directorate ;
  • Regional Planning Directorate supported by Norwegian Mapping Authority;
  • Cultural Heritage Management Directorate ; and
  • Organisation Economic Affairs Directorate .

4.3.2 Under the Norwegian law, every company is required to either compile a separate environmental report or devote a section in its annual report to its environmental policy and consequences. Environmental Impact Assessment (EIA) is required for every major project and the report is subject to public consultation. Although Norway is politically not part of the European Union (EU), it follows the economic policy of the EU and hence is committed to implementing all EU environmental directives.

Norwegian Pollution Control Agency (sft:) and pollution control in Norway

4.3.3 The Agency comprises five departments responsible for industry; environmental strategy; local environmental management; control and emergency response; and administration and information respectively. In Norway, the principal legislation is the Pollution Control Act enacted in 1981. It stipulates that pollution is forbidden unless it is specifically allowed by permits, regulations or ordinances. In essence, permits will need to be obtained from sft: before any activities which may or will result in pollution can be carried out. Appeals against the decisions of sft: can be made to the Ministry of Environment which will then be subject to judicial review by the Court. Third parties are also allowed to initiate appeals under the Norwegian system. Fees are payable in order to obtain the permits and fines will be levied in case of non-compliance. If there is serious violation of the permit conditions, the case will be referred to the Police for action. Directors of companies are also personally liable for any non-compliance or violation. The sft: has maintained a very comprehensive information system (INKOSYS) about the permit conditions stipulated for individual companies and the system is open for public access. This enables the sft: to minimize its policing work as the public will assume a major part of the monitoring responsibility.

Wastewater management in Norway

4.3.4 Water quality standards in Norway are set with reference to the background water quality and intended uses of the recipient water bodies. Relevant EU directives will be duly implemented. In the past 27 years, some 27 billion NOK (HK$24.3 billion, assuming exchange rate 1NOK=HK$0.9) was spent on waste water collection and treatment facilities but only some 5 billion NOK (HK$4.5 billion) was contributed by the Norwegian Government. The rest was funded by fees and charges collected from the end users. In addition, 95% of the operation and maintenance expenditure is recovered from fees and charges. The major remaining challenge is to achieve DO standard and in handling the polluted sediment in enclosed fjords where the waterflow is low.

Waste policy and incineration in Norway

4.3.5 The Norwegian Government has a policy to limit the growth in the volume of waste to a rate lower than the economic growth. It has also set a target that no more than 25% of the waste can be disposed of at landfills or incinerated without energy recovery by 2010. In Norway, there are altogether 14 municipal incinerators and 5 medical incinerators. These facilities can handle some 700,000 tonnes of waste annually at present. Altogether 16 new incinerators are under planning which will further increase the total capacity by another 400,000 tonnes per year. Currently, the Norwegian Government levies taxes on all final disposal of waste. Operators of landfills are required to pay a tax of 314 NOK (HK$282.6) per tonne whilst operators of incinerators are required to pay a tax ranging from $0-235 NOK (HK$0-211.5) per tonne, depending on the rate of energy recovery. Material recycling is not subject to any tax.

4.3.6 It is interesting to note that although Norway is not a member of the EU, it has signed an agreement to abide by the EU environmental directives.

4.3.7 Environmental education is under the Ministry of Education.

4.3.8 All listed companies must have a separate chapter in their annual report on environmental performance.


5.1 Visit to Cergy-Pontoise Waste Water Treatment Plant (CPWWTP)

5.1.1 The CPWWTP is located in Neuville sur Oise, France and has a capacity of 200,000 population equivalent, treating a flow of 40,000 m3/d. It is operated by Vivendi, a publicly listed company. The treatment process comprises coarse and fine screening, oil-grit removal and biological treatment in two stages. Stage 1 uses the activated sludge process followed by lamella sedimentation for the removal of carbonaceous pollution. Stage 2 is a BAF system using the BIOSTYR process for the removal of nitrogen. The BIOSTYR process consists of upflow filtration through a submerged and floating fine granular media called BioStyrene. Air is injected to the bed and the media itself will denitrify. However suggestion was made if an extra compartment was built below the bed and the treated effluent is pumped to the lower compartment as an anoxic zone, denitrification might be achieved. But this has yet to be proven. In the latter case, the filter can simultaneously nitrify and denitrify. As for the sludge treatment process, it includes thickening, anaerobic digestion, and mechanical dewatering by centrifugation. Throughout the process, there is good ventilation and foul-air extraction. Physio-chemical treatment is also used to minimize the odour problem.

5.1.2 The plant management professed that they would not want to be heavily involved with manufacturing equipment, preferring to buy the best from the market. Often, they will work together with the manufacturer.

5.2 Visit to Acheres Wastewater Treatment Plant

5.2.1 The plant was built in 1933 near Paris and has undergone four phases of expansion in 1940, 1966, 1972 and 1978. It is also operated by Vivendi. It is the largest STP in Europe using the conventional activated sludge process and has a treatment capacity of 1.94 million m3 per day with an additional 390,000 m3 per day standby capacity. In 1999, the Acheres plant was further expanded by providing a physiochemical process known as Actiflo. This new part of the plant was built to improve the overall effluent quality because the existing conventional activated sludge plant could not efficiently handle the wet weather flows. The Actiflo process combines the benefits of weighted flocculant and coagulant with lamella settling. It was claimed that the loading rate of the Actiflo process could be 180 times that of conventional primary settlement, or 20 times that of CEPT. Hence the space requirement would be much reduced. However, the design of Actiflo units at Acheres was less aggressive and was only at half of the maximum loading. It is installed after the fine screening and degritting stage. Downstream of the Actiflo, the treated water can be discharged directly into the river (during heavy storm) or sent to the conventional activated sludge process for further biological treatment. Sewage sludge is thickened and thermally conditioned.

5.2.2 It is worth noting that the extension plant was given a very impressive architectural treatment. This is important because there are residents about 2 km from the plant. It was understood that the residents were concerned about the visual impact and hence had a say in finalizing the architectural design of the plant.

5.3 Visit to Colombes Waste Water Treatment Plant

5.3.1 The Colombes WWTP near Paris was specially designed to cater for the narrowness of its 3-hectare site and its location in a highly built-up area. It has a capacity of 1 million population equivalent. The whole plant is completely covered so as to minimize any noise or odour problem. They claimed that the scrubber had never been used. Its construction took 4 years and involved digging a 15m deep pit in which an 800m long cast wall was installed. Then some 420,000 m3 of rubble were removed to provide the main chamber of the plant.

Main features of the Colombes WWTP

5.3.2 The plant is capable of adopting seven different water treatment configurations so as to adapt to all climatic conditions, especially during the summer storms. It treats a daily average of 240,000 m3 and 1,200,000 m3 sewage for dry weather and wet weather flows respectively. The sewage treatment process comprises preliminary screening, grit removal, physical-chemical primary treatment (the Densapag process) where precipitation of phosphorus and agglomeration of suspended solids by the addition of reagents and sludge takes place, lamellar settling, and finally biological treatment using the BAF process. Three separate stages of the BAF process are applied for carbon removal, nitrification and denitrification. There are 24 BAF units using Biofor for carbon removal, 29 units of Biostyr for nitrification and another 12 units of Biofor for denitrification. The three BAF stages can be operated in parallel or in series depending on the seasonal variation in the quantity of the influent flow. The effluent standard was set such that BOD and phosphorus removal is always required for all weather conditions, but various degree of nitrogen removal will be required depending on weather conditions. During the dry weather condition, sewage will be fully treated to achieve high nitrogen removal. During wet weather condition, only partial nitrogen removal will be achieved. During extreme storm condition, a nitrified effluent is all that is required. The plant has a very compact layout, occupying only four hectares of land in total. It was divided into two layers with the bottom layer used for sewage treatment and the upper layer for sludge treatment. Similar to the Achere plant, a lot of attention was paid to the architectural design. The treated effluent is discharged into the River Seine.

5.3.3 As for the disposal of sludge produced during the sewage treatment process, provision is made for two types of treatment, namely agricultural re-use or incineration (using 4 furnaces of which one is standby). The Agricultural re-use type of treatment involves thickening by air flotation, dewatering by centrifugation, sanitization cum stablization using lime treatment to destroy pathogenic germs and then transport by inland waterway or road transport. The incineration process involves thickening by air flotation, dewatering by centrifugation, incineration with heat recovery and exhaust gas treatment by dedusting, scrubbing, filtering and catalytic treatment.

5.3.4 The capital cost for the plant was US$300 million.

5.4 Visit to Azalys Waste to Energy Plant (AWEP)

5.4.1 The AWEP is located at Carrieres-sous-Poissy and has very impressive modern architecture which is very distinct from that of traditional incinerators. Its chimneys are short and well-integrated with the rest of the complex and are almost unnoticeable at a glance. The construction of the plant started in 1996 and was commissioned in 1998 under a Design-Build-Finance-Operate-Transfer arrangement. The company is entitled to operate the plant for 20 years before transferring the ownership to the municipal government. The AWEP currently handles 115,000 tonnes of domestic and assimilated waste per year. The plant has two 7.5 t/hr grate furnaces. The energy released by combustion of the waste is recovered by two vertical water tube boilers, in the form of super-heated steam directed to a turbo generator producing 70,000 MWh/yr of electricity. The electricity generated is sold to the national utility company's grid the income of which corresponds to about FF90/tonne of waste. The company currently charges FF450/tonne of waste, which is slightly higher than the norm in France (FF300-400/tonne). AWEP also has a waste reception facility to receive waste brought in from nearby communities. Environmental legislation in France required incinerator companies to recover recyclable waste before putting it through incineration plants. The AWEP currently recovers about 20% of waste delivered to them, comprising mainly paper, glass, iron and plastic. The standard for Dioxin emission is set at 0.1 ng/m3. The exhaust gas is treated by electrostatic precipitator, lime scrubber and catalytic converter. AWEP employs only 33 people to operate the plant. The slag from the incinerator is used as road base material in civil engineering projects.

5.4.2 They also left the architectural design to the local mayors.


6.1 Meeting with Dutch Ministry of Housing, Spatial Planning the Environment

6.1.1 The Dutch Strategic Environmental Assessment (SEA) process is set out below -

Screening of plan or project on environmental impact assessment (EIA) obligation with the application of criteria and thresholds
Arrow Down
EIA required;Possibility to apply for exemption
Arrow Down
Arrow DownNo EIA required

Arrow DownExemption granted
Exemption not requested or refused:Proponent prepares notification of intent
Arrow Down
Notification of intent is published by the authority
Arrow Down
Public consultation and scoping advice by the Independent Commission for EIA and environmental government agencies
Arrow Down
The authority issues plan or project specific guidelines for EIA content
Arrow Down
Proponent prepares EIA report
Arrow Down
Proponent prepares supplementary information if required by the Authority
Arrow Down
The authority decides on acceptability of EIA report
Arrow Down
Public consultation and quality review by the Independent Commission for EIA and environmental government agencies
Arrow Down
Decision and monitoring
The Authority takes decision in a written statement taking into account the EIA
Arrow Down
Mandatory monitoring and post decision evaluation by the Authority
Arrow Down
The Authority considers the potential consequences of results of the evaluation for the decision taken

6.1.2 The Commission for EIA is autonomous with a budget of its own subsidized by the Dutch Government, acting as an independent expert committee in all EIA processes taking place in the Netherlands. So far the Commission has issued technical advice on more than 1,000 projects and plans. The Commission acts through small working groups for each individual SEA.

6.1.3 In order to promote sustainable development and to highlight the environmental consequences of important legislation, the Dutch Government has introduced the E-test initiative in recent years. The E-test is an internal exercise within the Government whereby proponents of important pieces of legislation will be required to evaluate the environmental implications of their legislative initiatives and put forward their findings to the cabinet for consideration. The findings will also be disclosed to the public in due course. At present, only about 10% of the legislative initiatives do actually go through the process. There are different views regarding whether the E-test is effective for its intended purpose and some suggest that the SEA process should be extended to cover new legislative initiatives instead.

6.1.4 In common with other government bodies, they are concerned about how to keep the public informed and hence involved in the decision process.


7.1 Sewage Treatment

7.1.1 The delegation observes that the BAF technology is a very compact and effective sewage treatment technology. Its modular configuration allows great flexibility to deal with fluctuations in influent flow and to adjust the treatment process to meet different effluent standards within a relatively small footprint. Standby facilities can also be built in easily to cater for contingent events and additional flows. According to the information provided by the plants visited, the actual effluent standard does not only meet but sometimes surpass the stringent requirements stipulated by the regulatory authorities.

7.1.2 Over the past few years, many new BAF plants were commissioned and a lot of valuable experience will be available to Hong Kong to learn from the problems and mistakes encountered by other pioneers. For example, backwash design is very important to a BAF system and poor design could lead to significant media loss. The media loss does not only mean a higher operating cost due to frequent media replacements, but also gives rise to other operational problems such as pump blockage and odour. Both the Liverpool WWTP and the VEAS WWTP have experienced significant problems in this regard at some stage, although the problems were finally resolved.

7.1.3 Most of the plants visited by the delegation are run by the private sector. All of the plants are highly automated and only a few people, less than five in many cases, are on-site to operate the plants. In general, once the BAF system has been properly aligned, the experience overseas is that only minimal supervision is required round-the-clock.

7.1.4 Sludge produced during the sewage treatment process is usually disposed of in three ways: recycling for agricultural uses, landfill and incineration. If the sludge cannot be recycled for agricultural uses, disposal by means of incineration is usually preferred. Some of the plants visited by the delegation have on-site sludge incineration facilities.

7.1.5 In general, the sewage charges for the European countries are much higher than ours. Their sewage charges are usually linked to their water consumption level and people there generally accept that they should pay for both the capital and recurrent expenditure in connection with sewage treatment.

7.1.6 Sewage treatment plants can be built and operated in an enclosed area or underground. Special design shall be considered to minimize the visual impact on sensitive areas.

7.1.7 It is advisable for the plant operator to maintain a close working relationship with the BAF filter suppliers.

7.2 Waste Incineration

7.2.1 In general, Europeans widely accept that incineration is an environmentally friendly way of waste treatment, particular those with energy recovery. (Remark: The European Community (EU) will phase out landfilling of putrecible waste, but landfill will still be needed for accepting incinerator ash, construction waste, etc.. The phasing out of landfilling putrecible waste is a means to encouraging more composting and recycling, rather than to encourage incineration of these waste. EU prefers incineration of waste with energy recovery. This tends to favour waste having high calorific value and dry, like packaging waste (incidentally, these characteristics are not favourable to composting).

7.2.2 When it comes to the planning and construction of the actual facilities, the "not in my backyard" sentiment is still very common. The public consultation process often takes years before a consensus on the way forward can be reached. In this connection, it is noted that adoption of innovative and elegant architectural designs is an effective means to boost public acceptance. The marginal costs associated with such designs are widely perceived to be well justified.

7.2.3 According to the emission statistics provided by the incineration plants visited by the delegation in both Oslo and Paris, the actual undesirable emissions including dioxin from the incineration process seldom exceed the standards stipulated by their respective regulatory authorities. These incineration plants in fact claimed that the quality of their emissions was better than the air quality of their surrounding environment.

7.3 Environmental Impact Assessment

7.3.1 The EIA process in Hong Kong is comparable to the Dutch one which is often considered the most advanced in the world.

7.3.2 Even the Dutch people have reservations about changing the EIA process into legal proceedings as this would unduly prolong the planning and consultation process for major projects and make the whole process a very expensive exercise.

7.3.3 At present, the Dutch people have not yet come to a unanimous view on whether and how the EIA process should be extended to cover all major decision-making processes. They are also trying to map out their own way forward.

7.4 Sustainable Development

7.4.1 Sustainable development requires support from the highest level within a government and public awareness and cooperation.

7.4.2 Introduction of green tax is an effective means to provide an element of economic incentives in the promotion of sustainable development.


8.1 Sewage Treatment

8.1.1 BAF technology is a very compact and effective tertiary wastewater treatment technology when denitrification of the treated effluent is not required. If a higher level of denitrification is needed, an extra stage involving the addition of methanol (similar to the VEAS plant) might be required.

8.1.2 Consideration could be given to adopting the cavern/underground options in Hong Kong where land is scarce and developments are dense. Odour control will also be easier with this approach.

8.1.3 Whilst there is much confidence in BAF as a mature technology, careful pilot tests will be required. Smooth operation should not be assumed at early commissioning stage. A lot of follow-up work by the operator/contractor will be required to fine-tune the operation and the components of the system. The experience of BAF forerunners could contribute significantly to the design of BAF plants to reduce or avoid problems.

8.1.4 The use of the "Design-Build-Finance-Operate-Transfer" approach with specification of final effluent standards/quality objectives seems preferable, as this allows greater flexibility in adjustment of processes, and ensures optimal cost-effectiveness. Overseas experience also indicates that it would be advisable to require the operator/contractor to work closely with the stakeholders right from the beginning to solicit wider acceptance of a facility under planning.

8.1.5 A sound sewage charging scheme will be an important feature of the "Design-Build-Finance-Operate-Transfer" approach without which there will not be sufficient incentive for the potential operator/contractor.

8.1.6 When inviting tenders, the Administration should not be prescriptive and input specific. Instead it should concentrate on output and outcomes. It will be up to the tenderers to demonstrate their technology and how it would achieve or exceed the standards required.

8.2 Sludge & Solid Waste Treatment

8.2.1 There is confidence amongst the operators in pursuing waste incineration.

8.2.2 Resistance from residents near newly planned incinerators is likely. It is important to have early and proactive interactions with residents so as to allay unwarranted fears. There should also be greater transparency in consultation exercises. The inclusion of certain technical details in consultation exercises may be helpful.

8.2.3 The experience of using the contractor as an additional party to engage the stakeholders (in Azalys) in order to finalise the award of contract is worth noting.

8.2.4 Aesthetically pleasant architectural design is a worthwhile investment that can help win public acceptance of the facilities.

8.2.5 The use of the "Design-Build-Finance-Operate-Transfer" approach with specification of final standards/quality objectives is also relevant to the development of sludge and solid waste treatment facilities.

8.2.6 Overseas experience shows that a waste disposal charge should be acceptable to the public if there is sufficient education to convince them of the problem faced by the Administration on waste management.

8.2.7 The Administration should expediently forge community consensus on the development of waste-to-energy facilities in Hong Kong.

8.3 Environmental Impact Assessment

8.3.1 The Dutch experience in environmental impact assessment is valuable. There should be a continued dialogue between the Netherlands and Hong Kong to exchange experience and views on the environmental impact assessment process.

8.3.2 Conflicts between approving authority and project proponents/contractors over environmental impact assessment issues should be resolved through discussion instead of lawsuits.

8.3.3 The experience of the EIA Commission in the Netherlands has shown the merits of having an independent expert group to give expert advice to the government on the environmental acceptability of a project as well as to collate the views of the public.


9.1.1 The delegation wishes to thank the British Consulate-General in Hong Kong, the Hong Kong Consulates-General of France, Norway and the Netherlands, and the staff of the Economic and Trade Offices of the Hong Kong SAR Government in London and Brussels for the arrangements that they have made for the delegation before and during the visit. The delegation also wishes to express gratitude to all persons and organizations that have received them during the visit, as well as any persons who have provided advice or assistance in organizing the visit. Finally, the delegation wishes to thank the Secretariat of the Council for their hard work and excellent support services provided and the Environment and Food Bureau for funding part of the study visit.





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