Systems and methods for treating waste water

Abstract

Systems and methods for treating waste water containing biological wastes such as animal waste generated in livestock-raising operations, wherein the waste water is subjected to a series of operations to separate solids from the liquid phase of the waste water and to biologically treat the waste water to break down organic components. The separated solids are stored for further treatment or conversion into useful materials. The treated liquid phase can be put to various uses. In one embodiment, the treated liquid is recycled as flush water for flushing animal waste from an animal barn, whereby little or no liquid phase escapes the system into the surrounding environment.

1 - 20 . (canceled)  
     
     
         21 . A system for treating a stream of animal waste flushed from an animal barn with flush water, the stream having liquid components and solid components, the system comprising: 
 a skimmer apparatus comprising a holding tank for receiving the waste water and having a liquid outlet arranged below a level of an upper surface of the waste water in the holding tank through which liquid outlet the waste water is discharged from the holding tank, the skimmer apparatus further comprising a skimmer arranged for movement across the holding tank to skim floating solids from the upper surface of the waste water, and a solids receptacle for receiving the solids skimmed by the skimmer;    a system for introducing a coagulant into the waste water discharged from the liquid outlet of the holding tank so as to cause suspended solids in the waste water to coagulate;    a screening apparatus arranged to receive the waste water having the coagulant therein, the screening apparatus being structured and arranged to screen the waste water to remove coagulated suspended solids therefrom so as to create a solids stream and a liquid stream;    a settling tank arranged to receive the liquid stream from the screening apparatus and operable to allow suspended solids in the liquid stream to settle to a bottom of the settling tank, the settling tank having a solids outlet for discharging the settled solids and a liquid outlet for discharging liquid, and a connection between the solids outlet of the settling tank and the inlet of the skimmer apparatus for feeding the settled solids back to the skimmer apparatus; and    a biological reactor arranged to receive the liquid from the settling tank, the biological reactor comprising a vessel for holding the liquid from the settling tank, and an aerator disposed within the vessel and operable to inject air into the liquid for biologically treating the liquid, the biological reactor having an outlet for discharging treated waste water therefrom.    
     
     
         22 . The system of  claim 21 , further comprising an animal barn for housing animals, the animal barn having a waste removal system for flushing animal waste produced by the animals from the animal barn, the waste removal system having an inlet for flush water used for flushing the animal waste from the animal barn and an outlet through which the flush water and animal waste are discharged from the animal barn, and wherein the system is arranged such that waste water treated in the biological reactor is fed to the inlet of the waste removal system for the animal barn to be used as flush water to flush animal waste therefrom, and the flush water and animal waste from the animal barn are fed into the inlet of the skimmer apparatus.  
     
     
         23 . The system of  claim 22 , further comprising a clarifier arranged between the biological reactor and the animal barn for further treating the waste water before feeding the waste water back as flush water for the animal barn.  
     
     
         24 . The system of  claim 23 , wherein the air injected into the biological reactor is heated to a temperature exceeding ambient temperature prior to injection into the waste water, such that the waste water in the biological reactor becomes elevated in temperature.  
     
     
         25 . The system of  claim 24 , further comprising a holding reservoir, and wherein during cold ambient conditions the elevated-temperature waste water is fed from the clarifier back to the animal barn bypassing the holding reservoir such that the waste water helps heat the animal barn, and during warm ambient conditions the elevated-temperature waste water is fed from the clarifier to the holding reservoir where the waste water is cooled prior to being fed back to the animal barn.  
     
     
         26 . The system of  claim 25 , further comprising a clear well arranged to receive the elevated-temperature waste water from the clarifier during both cold and warm ambient conditions, and the waste water being fed from the clear well to the animal barn bypassing the holding reservoir during cold ambient conditions, and being fed from the clear well first to the holding reservoir and then to the animal barn during warm ambient conditions.  
     
     
         27 . A method for treating waste water, the waste water having liquid components and solid components, the method comprising the steps of: 
 holding a quantity of the waste water in a quiescent state in a holding tank to allow solids to float to the top of the waste water;    skimming solids from the top of the waste water and discharging liquid from the holding tank;    treating the liquid discharged from the holding tank with a coagulant to cause suspended solids in the liquid to coagulate;    screening the liquid treated with coagulant to removed coagulated solids therefrom; and    aerating the screened liquid in a biological reactor for biologically treating the waste water.    
     
     
         28 . The method of  claim 27 , wherein heated air is injected into the liquid in the biological reactor so as to maintain the liquid above a predetermined minimum temperature necessary for biological reaction to occur.  
     
     
         29 . The method of  claim 28 , wherein the waste water comprises animal waste flushed from an animal barn with flush water, and further comprising the step of using liquid discharged from the biological reactor as flush water for flushing animal waste from the animal barn.  
     
     
         30 . The method of  claim 29 , wherein during cold ambient conditions the liquid from the biological reactor is fed back to the animal barn along a first path, and during warm ambient conditions the liquid from the biological reactor is fed back to the animal barn along a second path different from the first path, the second path including a holding reservoir for holding the liquid to allow the liquid to cool prior to being fed to the animal barn.  
     
     
         31 . The method of  claim 29 , further comprising the step of feeding the flush water and animal waste from the animal barn to the holding tank.  
     
     
         32 . The method of  claim 27 , further comprising the step of reducing time-wise fluctuations in solids concentration of the waste water by passing the waste water discharged from the holding tank through an equalization tank.  
     
     
         33 . A skimmer apparatus for separating waste water into a first component comprising predominantly solids and a second component comprising predominantly liquid, the skimmer apparatus comprising: 
 a holding tank for holding a quantity of the waste water in a substantially quiescent state such that solids in the waste water float to the surface, the holding tank having a liquid outlet;    a solids receptacle adjacent one end of the holding tank;    a skimmer movable across the holding tank for skimming floating solids from the surface of the waste water into the solids receptacle;    a variable-geometry gate at the discharge end of the holding tank adjacent the solids receptacle, the variable-geometry gate being movable between a closed position in which the gate prevents floating solids in the holding tank from passing into the solids receptacle, and an open position in which the gate allows the floating solids to be swept by the skimmer into the solids receptacle, wherein the variable-geometry gate comprises a fixed lower portion and a movable upper portion, the upper portion in the closed position of the gate engaging the lower portion, the upper portion in the open position of the gate being pivoted away from the lower portion to create an opening in the gate through which the floating solids are swept by the skimmer into the solids receptacle.    
     
     
         34 . The skimmer apparatus of  claim 33 , further comprising: 
 a pump system connected to the liquid outlet of the holding tank; and    a control system operable to control the the pump system, the control system being operable to cause the pump system to pump liquid out from the holding tank so as to lower the level of the surface of the waste water in the holding tank to a level allowing the floating solids to be swept into the solids receptacle, and thereafter to cause the skimmer to begin moving across the holding tank towards the discharge end thereof.    
     
     
         35 . The skimmer apparatus of  claim 34 , wherein the control system is operable to periodically cycle operation of the pump system and skimmer so that discharging of liquid from the holding tank and skimming of solids into the solids receptacle occur on a periodic basis.  
     
     
         36 . The skimmer apparatus of  claim 33 , wherein the holding tank has a sludge outlet arranged at a bottom of the holding tank for discharging sludge that has settled to the bottom.  
     
     
         37 . The skimmer apparatus of  claim 33 , further comprising a conveyor arranged to convey solids out from the solids receptacle.  
     
     
         38 . The skimmer apparatus of  claim 37 , wherein the conveyor comprises a screw conveyor.  
     
     
         39 . The skimmer apparatus of  claim 33 , wherein the solids receptacle is disposed within the holding tank adjacent the one end thereof, the solids receptacle being formed by perforated walls that allow liquid to freely pass therethrough while preventing at least some solids from passing.  
     
     
         40 . The skimmer apparatus of  claim 39 , wherein one of the walls of the solids receptacle forms the fixed lower portion of the gate.  
     
     
         41 . The skimmer apparatus of  claim 39 , wherein an inlet for feeding waste water into the skimmer apparatus is arranged such that the waste water is fed into the solids receptacle so that larger bodies of solids are screened out by the solids receptacle.  
     
     
         42 . The skimmer apparatus of  claim 33 , wherein the skimmer is structured and arranged to push the movable upper portion of the gate open when the skimmer nears the gate.  
     
     
         43 . The skimmer apparatus of  claim 33 , further comprising a defoamer operable to spray water onto the surface of the waste water in the holding tank to knock down foam that forms on the surface.  
     
     
         44 . The skimmer apparatus of  claim 43 , wherein the defoamer is mounted on the skimmer.  
     
     
         45 . A screening apparatus for treating a mixture containing liquid and solid animal waste, comprising: 
 a fine-mesh screen arranged in an inclined orientation, the screen having an upper end and a lower end and having an upper surface, the screen allowing liquid to flow downwardly through apertures therein while preventing solids larger than said apertures from passing through the screen;    an inlet arranged proximate the upper end of the screen for feeding the mixture onto the upper surface of the screen such that the mixture flows downward along the screen toward the lower end thereof; and    a plurality of substantially liquid-impervious squeegees connected to a drive member arranged in an endless loop and driven by a motor, the squeegees being spaced apart about the loop of the drive member, the squeegees contacting the upper surface of the screen and being driven by the drive member to move downward along the upper surface of the screen so as to scrape solids from the screen, the squeegees also serving as dams operable to prevent the mixture from flowing past the squeegees along the screen such that residence time of the mixture on the screen is increased.