The waiver on refuse charges is operated by the Local Authorities, not Dept of Social Welfare. Local Authorities may use the Social Welfare payment rates as guidelines when determining eligibility for a waiver.
As Battyee said, only a percentage of OAPs qualify, because of additional income (e.g. an occupational pension) in addition to the State Pension.
From the Citizens information website:
"In some local authority areas, low-income households can avail of a waiver on waste charges by private refuse operators and local authorities. These waivers vary greatly from region to region and in some areas they are not available at all. To find out if your local authority operates this waiver scheme, you should contact them directly."