Cape Town water department cash crunch

I read with dismay Cape Town Councillor Limberg's statement:

"Our finance team is working on making funding sources available, including cash, reprioritisation of existing water projects, a concessionary loan from an external funder, and curtailing expenditure elsewhere in the administration," Limberg said.

Page 140 of the 2017/2018 budget (under debt inpariments) reflects that Department of Water and Sanitation expects to write off R894 m this year, R1bn next year and R1.1bn in the year 2019/2020. Massive amounts of money!T his equates to 15% of its revenue!

Who are these people that owe so much, who pays for this and why are they not being hauled before the courts like residents are when they don't pay their rates bills?

How much has been written off since say 2010? Enough to pay for a 500ml litre a month desalination plant? 

Answers please Councillor Limberg!