Abstract A liquid wastes treatment system, including a two-stage, highrate, activated, biological filter is disclosed. An activated floc, similar to that found in activated sludge processes, is built up in the biological filter by recycling substantial quantities of aerobic sludge from a secondary clarifier to the biological filter and by metering the solids wasted from the treatment system to maintain the mixed liquor, suspended solids level in the filter effluent in excess of about 1,500 mg./1. Underdrain flow from the secondary clarifier is a substantial percentage of plant influent flow and is recycled without extended mixing with plant influent or aeration prior to distribution over the biological filter. The filter media is preferably an array of lathes formed to provide many horizontal surfaces on which floc will form. When a two-stage system is employed, including a primary clarifier, wasting is preferably accomplished by returning activated floc and biological slime sloughed from the biological filter to the primary clarifier and wasting solids from the primary clarifier, which also results in improved primary clarification.
A process for treating liquid wastes as defined in claim 1 wherein, said biological filter is selected to have a gridlike array including a plurality of horizontally and vertically spaced rows of elongate members and means formed to secure said members in fixed relation, each of said members being formed with a transverse cross section defined by an upwardly and downwardly facing pair of substantially horizontally disposed and oriented roughened surfaces and connecting vertically extending surfaces of an area less than the area of said horizontal surfaces, said upwardly facing surfaces affording an area upon which a quantity of activated solids may be stored in said filter for contact with said liquid wastes.
Claim 2
Dependent Claim
36 words
A process for treating liquid wastes as defined in claim 1 and the step of: maintaining the mixed liquor, suspended solids level in the filter effluent in the range of about 1,500 to about 6,000 mg./l.
Claim 3
Dependent Claim
77 words
A liquid wastes treatment process as defined in claim 1, and a. conveying a portion of said filter effluent directly over said filter while conveying the remainder of said filter effluent to said secondary clarifier; b. maintaining the total volume of said portion of said filter effluent conveyed over said filter and said sludge conveyed over said filter at a level no greater than about 2.5 times the volume of said liquid wastes distributed over said filter.
Claim 4
Dependent Claim
272 words
In a liquid wastes treatment System including a biological filter, distribution means for distribution influent in the form of liquid wastes over said filter, collecting means formed for collecting effluent from said filter, a secondary clarifier, and conduit means connecting said collecting means to said secondary clarifier for flow of filter effluent from said collecting means to said secondary clarifier, the process of treating liquid wastes comprising the steps of: a. employing a biological filter having a gridlike array including a plurality of horizontally spaced and vertically aligned rows of vertically spaced elongate members and means formed to secure said members in fixed space relation, each of said members being formed with a transverse cross section defined by a pair of substantially horizontally disposed and oriented roughened surfaces of substantial area and connecting vertically extending surfaces of insubstantial vertical dimension, said means further being formed and positioned so that the major portion of the downward flow of liquid wastes in said array occurs by the free fall of droplets of liquid wastes from one member to a vertically adjacent member, said vertically spaced members being positioned with the immediately vertically adjacent members in vertical alignment to form said vertically aligned rows; b. providing second conduit means from said secondary clarifier to said distributing means for recycling of waste materials over said filter; c. withdrawing aerobic sludge from said secondary clarifier and conveying the same without detention for further oxidation to said filter through said second conduit means and distributing means; and d. maintaining the solids in the filter effluent at a mixed liquor, suspended solids level in excess of about 1,500 mg./l.