Parents wishing to teach their kids valuable lessons on water conservation and renewal, should head over to Deer Island during April vacation week for a 2.6-mile hike around the nation's second largest waste water treatment plant.

The Deer Island plant - headed by the Massachusetts Water Resources Authority (MWRA) - serves 43 communities and 2.5 million people in eastern Massachusetts, taking in roughly 350 million gallons of wastewater a day.

"That's enough to fill the Prudential Building three times over,'' said Meg Tabacsko, education manager at the MWRA.

Wastewater is cleaned and treated at the plant and re-released in to Boston Harbor where it gets cycled back in to household use, and eventually ends up back at Deer Island.

"I like to remind children that all the water we have on earth today is all the water d lwe've ever had,'' Tabacsko said. "All the water that we have has been used before and will be used again, which is why we build plants like Deer Island so that it can be cleaned and safely returned to the environment.''

In addition to treating water, the plant processes wastewater sludge for recycled use as Bay State fertilizer, said Tabacsko.

The island's many trails offer scenic views of the plant's historic pump station and surrounding harbor islands and an up-close look at the 12 towering egg-shaped sludge digesters. Before heading out, Tabacsko suggests downloading a scavenger hunt field guide from the MWRA's website - www.mwra.state.ma.us.

"A local teacher, Bev Hinckley of the Horace Mann Elementary School in Melrose, put together the scavenger hunt field guide for the perimeter walk,'' said Tabacsko. " She takes her students every year. They take their clipboards and are totally engaged.''

The guide asks that kids identify harbor islands, hike up hills for sweeping views of the harbor and Boston skyline and perform mathematic equations to determine the size and diameter of the egg-shaped sludge digesters and the number of households served by the plant.

• South Shore Science Center
• New England Aquarium
• Deer Island
• EcoTarium