CONCENTRATIONS, SIGNIFICANT CUSTOMERS, COMMITMENTS AND CONTINGENCIES - Customer Concentrations (Details) - Customer concentration risk	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Revenues | Customer 1
Revenue, Major Customer
Concentration percentage (as a percent)	27.00%	47.00%
Revenues | Customer 1 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	48.00%	58.00%
Revenues | Customer 1 | Refining
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 1 | Recovery
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 2
Revenue, Major Customer
Concentration percentage (as a percent)	7.00%	10.00%
Revenues | Customer 2 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	13.00%	13.00%
Revenues | Customer 2 | Refining
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 2 | Recovery
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 3
Revenue, Major Customer
Concentration percentage (as a percent)	1.00%	4.00%
Revenues | Customer 3 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 3 | Refining
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 3 | Recovery
Revenue, Major Customer
Concentration percentage (as a percent)	9.00%	37.00%
Revenues | Customer 4
Revenue, Major Customer
Concentration percentage (as a percent)	10.00%	0.00%
Revenues | Customer 4 | Black Oil
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Revenues | Customer 4 | Refining
Revenue, Major Customer
Concentration percentage (as a percent)	30.00%	0.00%
Revenues | Customer 4 | Recovery
Revenue, Major Customer
Concentration percentage (as a percent)	0.00%	0.00%
Receivables | Customer 1
Revenue, Major Customer
Concentration percentage (as a percent)	15.00%	23.00%
Receivables | Customer 2
Revenue, Major Customer
Concentration percentage (as a percent)	17.00%	18.00%
Receivables | Customer 3
Revenue, Major Customer
Concentration percentage (as a percent)	4.00%	11.00%
Receivables | Customer 4
Revenue, Major Customer
Concentration percentage (as a percent)	7.00%	0.00%