Big stink as Pearl River Delta battles a rising tide of sewage

PUBLISHED : Saturday, 30 January, 2010, 12:00am
UPDATED : Saturday, 30 January, 2010, 12:00am

Officials in the heavily polluted Pearl River Delta are waging war on sewage sludge swamping the region. Winning the war, however, might be difficult.

It's well known that Guangdong has a big problem. Foul-smelling landfills are filling up and waste incinerators are being planned close to residential areas, sparking protests about health concerns.

But while most of the focus is on garbage disposal, the battle against less visible sewage sludge - a soupy residue of foul water left over from the treatment of human and other waste that circulates without appropriate treatment and disposal - is just as daunting.

Guangdong's Environmental Protection Bureau says the province dumped 6.9 billion tonnes of sewage into the sea in 2007. And nearly a fifth of its coastal waters were polluted by industrial waste and domestic sewage, according to the province's Oceanic Environment Quality Report.

Sludge treatment is a critical stage in urban sewage processing. Every 10,000 tonnes of sewage generates up to 1.5 tonnes of sludge. Guangzhou is expected to produce 830,000 tonnes of it this year.

At the end of 2008, the provincial government began collecting a household sewage processing fee, after introducing charges for the handling of urban waste in 1999.

But that has not stopped residents, from taxi drivers to academics, asking how the richest provincial government on the mainland has found itself up to its neck in excrement.

Effective sludge treatment can prevent toxic substances such as heavy metals from entering the environment. Dumping and burning are two common forms of treatment but burning pollutes the air and burying takes up land and risks polluting underground water.

Many countries have turned to converting treated sludge into agricultural compost but it is still difficult to get rid of heavy metal sediments and organic substances.

The mainland is expected to produce 27.7 million tonnes of sewage sludge this year but urban sludge treatment has only been on the national agenda since the 1990s.

Tackling the problem requires huge investment and advanced technology and the country is still struggling to find effective technologies for treating industrial and domestic waste.

Guangzhou Luyou group says reducing the water content in treated sludge is one feasible solution.

The treated sludge is drier, smaller and harder, making handling much easier. The privately owned waste-processing specialist, based in the provincial capital, has spent 50 million yuan (HK$56.83 million) researching sludge treatment technology and says it has achieved a breakthrough, which it demonstrates at a sludge treatment plant half an hour's drive from Guangzhou's Panyu district.

Relying on a secret additive and machines imported from Australia to condition and compress sewage sludge, it claims to be able to reduce the water content of sludge from 70 per cent to 55 per cent or less. The drier sludge can be used in various ways.

Guangzhou Luyou says sludge with heavy metal content below national limits can be used as organic fertiliser, while sludge that exceeds those limits can be used to produce fuel. Ash from incineration can be used to make bricks.

It says the whole package of technology is energy efficient, cheap and environmentally friendly.

However, sceptics abound, with many in the waste-processing industry saying the mainland lacks the stringent management and monitoring systems needed to make such a scheme work across the nation.

They say fundamental re-planning is needed, from urban sewage collection to treatment and disposal - and that is an extremely complicated task.

Others have praised the group's technology but say it seems to replicate developments overseas, rather than being the breakthrough it claims.

In Europe, recycling of treated sewage sludge for agricultural use is common and regarded as the best option for the environment. More than 40 per cent of European Union sewage sludge ends up in agriculture, although the actual percentage varies from country to country.

Last year, China's environment, science and technology, and urban construction ministries released a pilot policy guideline on domestic sludge and sewage. It included pledges to boost funding for sewage treatment and encouragement for private enterprises investing in treatment technology. However, realistic support is still pending.

With such a critical battle to fight, private enterprises should not be fighting the battle alone.

They deserve concrete help from government to support research and development - as well as good policies to enable effective implementation.