8 Things To Know About Recycling Water
By Yuanchao Xu 19 October, 2016
Recycling water could help alleviate some of China's water challenges. Check out 8 things to know about recycling
China’s water challenges are vast. The average annual water shortage of China is 50 billion m3. Even with the South-to-North-Water-Transfer project, water-recipient areas like Beijing and other cities in the Hai river basin will still have less water than international recognised water scarcity levels.
To reduce the country’s water challenges, China wants to comprehensively advance the construction of a water conservation society as shown in the 13th Five Year Plan (13FYP). Water recycling and the use of unconventional water resources are highlighted in the plan.
China’s 13FYP highlights water recycling & the use of unconventional water resources
Unconventional water resources refer to reclaimed water from wastewater treatment plants, desalinated seawater and rainwater harvested in sponge cities. They provide another option for water consumers.
Here are 8 things you should know about recycling water in China:
1. Various policies recently released on water recycling
Together with the 13FYP, a series of policies about water recycling have been issued recently (listed below).
2. Over 80% of wastewater is treated but only 10% is recycled
Reclaimed water, which refers to the treatment and recycling of wastewater, is the most common unconventional water resource.
China’s total wastewater discharge increased from 61.7bn t to 71.6bn t from 2010 to 2014
China’s rapid urbanisation and industrialisation over the past few decades have led to large increases in wastewater discharge. China’s total wastewater discharge (mainly industrial and domestic wastewater) rose from 61.7 billion tonnes to 71.6 billion tonnes from 2010 to 2014.
The chart below (click on to enlarge) shows that between 2010 and 2014, domestic wastewater discharge increased (38 billion tonnes to 51 billion tonnes) while industrial wastewater discharge slightly decreased from 23.8 billion tonnes to 20.5 billion tonnes. The increase in domestic wastewater is probably caused by rapid urbanization.
Increasing wastewater discharge implies increasing water consumption, wastewater treatment demand, as well as the potential of reclaimed water use. The above right chart shows that in urban areas, while the wastewater discharge increased, the amount of wastewater treated also increased. Actually, it did so at a faster pace. However, the amount of wastewater recycled and reused remains low at only around 10% of the wastewater treated. Great opportunities exist.
3. Over 99% of cities in China are equipped with wastewater treatment plants
Currently, the use of reclaimed water is the main form of water recycling. And it depends largely on the wastewater treatment industry.
China began to focus its efforts towards wastewater treatment in 1998, with further efforts followed with the 11FYP and 12FYP, which facilitated the construction of wastewater treatment plants and drainage networks. By 2014, over 99% of cities in China had at least some wastewater treatment plants.
Despite the extensive coverage of treatment, excessive discharge, imperfect drainage networks and profitability concerns remain challenges for some local governments and managers of those plants.
4. Challenges remain such as low quality reclaimed water, low profitability & more
Reclaimed water needs to fulfil certain requirements in order to be reused. Naturally, low quality reclaimed water hampers its use. An investigation by the Xinhua News Agency in 2014 showed that many treatment plants provide low quality reclaimed water. High retrofitting costs, inappropriate design of treatment plants and poor management may be to blame.
Water treatment fees paid are only about 1/3 of the actual cost
Low profitability is a significant problem. Researchers from Renmin University analysed data of 227 treatment plants. The results revealed that, depending on location, the average cost of treatment plants (operational cost and construction cost) is RMB2.73/m3. This is almost three times higher than the local average wastewater treatment fee paid to treatment plants, which is RMB0.76 (resident) and RMB0.98 (non-resident). This disparity between actual cost and fees received makes profitability very difficult.
5. China’s seawater use & desalination capability have been increasing over the last 15+ years
The “Special Plan for Seawater Usage” issued in 2005, provided plans and guidance for seawater usage. It contains 10 key projects related to seawater usage, including seawater usage in cooling for different industries, domestic water use, drinking water and cleaning. It also stipulates that China will establish over 6 seawater use demonstration cities or islands for seawater usage by 2020.
There are two main ways of using seawater: direct use & use after desalination.
There are 2 main ways of using seawater: direct use & use after desalination
Direct seawater use usually refers to the use of seawater in cooling applications of coastal power plants and petrochemical industries. As shown in our report Towards Water Risk Valuation, certain listed power companies generate up to 53% of their power using seawater cooling.
China initiated seawater desalination projects in the 1960s and has made substantial progress in recent years. According to the Seawater Usage Communique, from 2001 to 2015, China’s seawater desalination capability increased from less than 50,000 tonnes/day to 1,000,000 tonnes/day. A 1,000-tonnes/day seawater desalination plant on Yongxing Island was just put into use on 1 October 2016. Nowadays on Yongxing Island, desalinated seawater is able to fully satisfy the water use of its residents. In 2015, the top 3 desalinated seawater users were domestic water use (32.8%), thermal power plants (31%), and petrochemical industries (12.5%).
However, there are also many constraints. These include the relatively high desalination cost and associate energy consumption, the technology gap, incomplete seawater management, problems in including seawater in the water distribution scheme, and public understanding and acceptance of seawater desalination. Promisingly, the State Oceanic Administration (SOA) has started to search for solutions and collaborations for these.
6. Sponge cities: a way to collect and reuse rainwater
Sponge cites are known to help with flood control though they can also contribute to rainwater reuse. The concept of sponge cities was raised in 2012, then emphasized by President Xi Jingping in the Central Government Conference on Urbanization in December 2013. For more see our article here.
Sponge cities store rainwater and reuse it through different methods. These include:
- Wet ponds – which are mainly used for landscaping purposes;
- Cisterns (a waterproof receptacle for holding liquids) and rainwater tanks – store rainwater for afforestation, road spray, flushing water; and
- Constructed wetlands (treatment systems that use natural processes involving wetland vegetation, soils, and their associated microbial assemblages to improve water quality) – filters & purifies rainwater for further use.
7. Water consuming industries are also recycling water
Water consuming industries including coal mining and power also recycle water. Mine water collected from coal mines and coal washing water is usually recycled and reused. The government has standards and requirements for the water recycling rate for the mining industry. In the power sector, wastewater from cooling towers is reused for cleaning and spraying, and some ash water is reused in the cooling system. Some companies have their own wastewater treatment plants on site where wastewater can be treated and recycled directly within the company.
8. Membrane bioreactor: a promising technology for water recycling
MBR (Membrane Bioreactor) technology is commonly used in water recycling like wastewater treatment and seawater desalination. It is becoming more popular and is increasingly promoted by policies. For instance, the ‘Notice on Accelerating the Development of Energy-saving and Environmental Protection Industry’
With MBRs water can pass through the membrane while pollutants can’t & are instead biologically treated
MBR is a combination of membrane and traditional biological approaches: water molecules can pass through the membrane while pollutants cannot and are treated by biological approaches. Advantage of MBR includes high quality of treated water, little sludge generation and little space occupation, but there is also high cost and high power consumption to consider.
The good news is that costs are reducing with innovations, as pointed out by Frost & Sullivan Environment (Water) Practice. Investment and operation cost (energy cost, labour cost and materials) for MBR will probably be reduced by about 15-20% in the next few years.
China’s water recycling industry is becoming more important as the country looks to grow whilst consuming less resources. However, despite promotion by the government and evironmental experts there are some general obstacles to address including technology, profitability and public awareness on the use of recycled water.
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