Man’s effect on the environment Pollution

Pollution is any undesirable change in the physical, chemical and biological characteristics of our environment (air, water and land) and is mainly the result of man's activity.

Pollutants

The population equation: increase in population X wants for higher living standard

Biodegradable

Non-Biodegradable

Air pollution

Air pollution in HK

Air pollutants

smog

Temperature inversion

Photochemical smog Photochemical smog is the brown haze that develops in sunny cities. Photochemical smog is formed by the action of sun light on pollutants such as hydrocarbons and nitrogen oxides. These mixture forms a brownish color.In the troposphere, ozone is a pollutant that can irritate the eyes,throat,and lungs. Plants and other living things get harmed by this.

Health hazards of particulates matter (pm)

RSP The human nostrils filter out 99% of the inhaled large and medium sized particles (Table 4). The rest may enter the windpipe and lungs (Fig. 4) where some inhalable particulates cling to protective mucous and are removed. Some of the smallest particles, called respirable particulates may tend to be deposited in the alveoli (tiny air sacs in the lungs). In the lungs, particulates slow down the exchange of oxygen with carbon dioxide in the blood, causing shortness of breath. The heart gets strained, because it works harder to compensate for oxygen loss. Usually, people most sensitive to these conditions have respiratory diseases like emphysema, bronchitis, asthma or heart problems. Particles themselves may be poisonous if inhaled, damaging remote organs like the kidneys or liver. Swallowed mucous that is laden with hazardous particulate matter may damage the stomach.

Lichen-indicator of air pollution

Acid rain

Acid rain kills forests

Acid rain kills lakes

Water pollution

domestic

stream

Clean water species

Polluted water species

E. Coli – faecal pollution

Red tide

Hypoxia

Oil spills

Sewage treatment

Primary treatment preliminary treatment comprising coarse screening and grit removal and sedimentation.

Biological treatment It is essentially an ‘aerobic biochemical oxidation’ or aeration. In this process, sewage water is filtered through specially designed sprinkling filters so that aerobic conditions are maintained all the times.

Aerobic oxidation During this aerobic oxidation process, the carbon of the organic matter is converted in to CO2; the nitrogen into NH3 and finally into nitrites and nitrates.

Anaerobic digester organic matter is decomposed by anaerobic bacteria. The decomposition process produces a gaseous byproduct often called biogas, which consists primarily of methane, carbon dioxide, and hydrogen sulfide.

Anaerobic digester                                                               

Biogas production To optimize the digestion process, the bio-digester must be kept at a consistent temperature. Most digestion vessels require some level of insulation and/or heating. Some installations circulate the coolant from their biogas-powered engines in or around the digester to keep it warm, while others burn part of the biogas to heat the digester.

Anaerobic digestion helps stabilize Sludge Primary and activated sludges are treated in digesters running at a fairly constant 35°C, which break down the volatile organic matter to produce a stable sludge, The material drawn from the anaerobic digester is called sludge. It is rich in nutrients (ammonia, phosphorus, potassium, and more than a dozen trace elements) and is an excellent soil conditioner. It can also be used as a livestock feed additive when dried. Any toxic compounds (pesticides, etc.) that are in the digester feedstock material may become concentrated in the effluent. Therefore, it is important to test the effluent before using it on a large scale. In HK, sludge is subsequently dewatered via centrifuges before being transported off-site for disposal in landfill.

Tertiary treatment The First Tertiary Sewage Treatment Plant with Reclaimed Water Facilities in Hong Kong Ngong Ping STW cum Ngong Ping Sewage Treatment Information Centre was commissioned on 18 March 2006. It adopts advanced biological, filtering and disinfection technology in the treatment of sewage. The effluent after chlorination process becomes safe and reusable reclaimed water, which is conveyed to nearby public toilets, toilets in the Ngong Ping Cable Car Terminal and associated tourist facilities for flushing use. Besides, part of the reclaimed water is used inside the treatment works for rearing aquarium fishes and controlled irrigation.

Reuse of reclaimed water "NEWater" the name given to potable, recycled water produced by Singapore's Public Utilities Board. The purification method uses dual-membrane (via microfiltration and reverse osmosis) and ultraviolet technologies, in addition to conventional water treatment processes.

Options for Sustainable Waste Management for Hong Kong

WASTE MANAGEMENT HIERARCHY 1. Avoid waste generation 2. Minimize waste generation 3. Reuse/Recycle the material 4. Waste treatment 5. Landfill disposal AVOID MINIMIZE REUSE/RECYCLE TREATMENT/ DISPOSAL

Municipal Solid Waste (MSW) Generation in Hong Kong 香港的都市固體廢物生產量 Disposed of at landfills 3.4 million tonnes 棄置於堆填區三百四十萬公噸 Recovered 2.3 million tonnes 回收再造二百三十萬公噸 40 % 60% Hong Kong generated 5.7 million tonnes MSW in 2004 香港於2004年共產生五百七十萬公噸都市固體廢物

MEASURES TO AVOID/REDUCE/RECYCLE WASTE Education Waste charges Product Responsibility Scheme (PRS) Territory-wide source separation of waste Appropriate use of RCP and RTS

Material Recovery Facilities of Recyclables (Dirty MRF) Management Options of Residual Waste after On-site Separation/Recycling Direct Landfilling Material Recovery Facilities of Recyclables (Dirty MRF) 2) Mechanical and biological treatment before landfilling 4) Thermal treatment before landfilling 5) Thermal treatment and reuse of ash

CURRENT SITUATION IN HK Total reliance on landfilling for non-recycled waste

N Landfills RTSs Special Waste Facilities NENT Landfill WENT Landfill Guangdong Sheng N NENT Landfill SENT Landfill WENT Landfill RTSs Landfills Special Waste Facilities

3 Strategic Landfills 稔灣 打鼓嶺 將軍澳 Nim Wan Ta Kwu Ling Tseung Kwan O Source : EPD

海外國家的都市固體廢物管理 Municipal Solid Waste Management in Other Countries 58

Problems of Traditional Thermal Treatment Technologies Flue gas emission Ash residues are toxic (heavy metals and dioxin) Residues still account for 10-15% of waste input volume Construction cost and processing cost are higher than landfill

Advances in Thermal Waste Treatment Technologies Conventional Incineration 　 　 Dioxin problem Exhaust gas and ash New Technologies Clean flue gas Decompose dioxin Containment of heavy metals in vitrified slag 60

Reality for Hong Kong Hong Kong cannot afford to build new landfills to manage our solid waste

Examples in Tokyo and Singapore show a small landfill can meet the disposal requirements of thermally treated residuals of MSW

Major Issues What is the maximum waste recycling rate ? What is the minimum waste quantity requiring disposal ? Zero waste or zero landfill ? Landfill or thermal treatment for non recyclables ?

RECOMMENDATIONS FOR HK Improve infrastructure to facilitate source separation and recycling of domestic waste Implement product responsibility schemes to reduce waste ASAP Appropriate economic instruments and charges to encourage waste reduction/recycling ASAP 3. Develop a more stable and healthy local waste recycling industry (Eco-park and long term policy) 4. Adopt appropriate waste treatment methods (vol. reduction) –Decision is needed ASAP