Read the passage given below and answer the question.

Pollution Control Boards

In order to address two major environmental concerns in India, viz. water and air pollution, the government set up the Central Pollution Control Board (CPCB) in 1974. This was followed by states establishing their own state level boards to address all the environmental concerns. They investigate, collect and disseminate information relating to water, air and land pollution, lay down standards for sewage/trade effluent and emissions. These boards provide technical assistance to Governments in promoting cleanliness of streams and wells by prevention, control and abatement of water pollution, and improve the quality of air and to prevent, control or abate air pollution in the country.

These boards also carry out and sponsor investigation and research relating to problems of water and air pollution and for their prevention, control or abatement. They also organise, through mass media, a comprehensive mass awareness programme for the same. The PCBs prepare manuals, codes and guidelines relating to treatment and disposal of sewage and trade effluents.

They assess the air quality through regulation of industries. In fact, state boards, through their district level officials, periodically inspect every industry under their jurisdiction to assess the adequacy of treatment measures provided to treat the effluent and gaseous emissions. It also provides background air quality data needed for industrial siting and town planning.

The pollution control boards collect, collate and disseminate technical and statistical data relating to water pollution. They monitor the quality of water in 125 rivers (including the tributaries), wells, lakes, creeks, ponds, tanks, drains and canals.

CPCB prepares manuals, codes and guidelines for which of the following purpose?

Treatment and disposal of sewage

The passage states that the Central Pollution Control Board (CPCB) prepares manuals, codes, and guidelines relating to the treatment and disposal of sewage and trade effluents. This suggests that the CPCB's primary focus is on developing and disseminating information about effective sewage management practices.

The other options, while potentially relevant to environmental protection, are not directly mentioned in the passage as areas of focus for the CPCB's manuals, codes, and guidelines.