Recycling Wastewater

Project 1

Integrated Cattle and Aquaculture Project

Link to Publications

Click here for detailed description

Summary :

This project collects and treats water and animal manures from the Texas Tech University Animal Science Facility near New Deal, Texas. The Animal Science Facility contains a horse barn and facilities (1), a sheep center (2), a horticultural center (3), an operations facility (4), a swine research center (5), an area for machine storage (6), a feedmill and roughage storage station (7), cattle pens and feedlot (8), a beef cattle center (9) and a dairy barn (10). Currently, water and manure, collected from up to 1000 head of cattle standing on slotted floors in pens and from 180 sows farrow-to-finish swine facility(cleaned with a flushing system), are discharged to primary (11) and then secondary (12) settling ponds followed by final discharge into a playa lake (13). A diversion box and sump pump (20) have been installed to redirect the animal waste and process water from the settling pond to an integrated facultative pond (15) with a 20-foot deep anaerobic pit (16). The pit has been designed for recovery of biogas to be used on-site for production of steam and electrical energy. Methane is captured by a membrane stretched over the 35 x 35 ft pit. Subsurface water collectors have been placed at 1 and 5 feet below the bottom of the pond to sample water infiltration from the pond. Water samples can be withdrawn through a network of over 2.5 miles of pipes and tubing to a central collection point for analysis of quantity and quality. One half of the pit bottom was sealed with cattle manure packed in place. The other half of the bottom was sealed only through the deposition of solids in the waste water stream. The collection of infiltration water from below the pit and pond will be analyzed to determine the level of sealing that occurs from the deposition of manure solids. Water from the integrated facultative pond flows through one of the diversion boxes (14) into a pond for production of aquatic plants. Plants in this pond (18) will remove nitrogen and phosphorus thereby improving quality of the effluent. Plants with economic value such as water lilies (ornamentals) and duckweed (potential cattle feed) will be cultured. The final phase of water treatment will be on-site production of aquatic organisms, such as fish, to feed on and thus remove organic materials produced in the system. Water from the fish pond will be diverted back to the playa lake (13).

Project 2

Pilot Scale Water Reuse System

Link to Publications

Click here for detailed description

Summary :

A 23-tank, 43 m2, pilot-scale constructed wetland system was loaded daily with 136.2 liters of cattle feedlot wastewater to measure the nitrogen removal effectiveness. The 23-tanks were separated into six different treatment series, and the effects of four different total nitrogen (TN) loading rates were investigated with three different series surface areas and detention times. The four TN loading rates were 11.4, 8.0, 2.3, and 0.5 g TN/day. All four loading rates were tested in treatment series consisting of four tanks. Additionally, the 2.3 g TN/day loading rate was tested in a series with two tanks and a series with five tanks. The removal of nitrogen constituents from wastewater is dominated by maximizing the permanent removal processes inherent to the nitrogen cycle. Although the nitrogen cycle is a complex interaction of biological and chemical phenomena, maximizing its inherent removal processes is attainable in the wetland environment. The primary facilitator of this nitrogen removal is the root-zone aeration of the predominantly anaerobic environment surrounding the wetland soil. Given proper amounts of dissolved oxygen, the microbiota of nitrification can oxidize ammonia to nitrate, and denitrification can take place in the anaerobic environment, ultimately removing nitrogen from the wastewater in the form of nitrogen gas. An additional permanent nitrogen removal pathway in wetlands is defined by the plant uptake of ammonia and/or nitrate. However, maximizing this removal pathway requires plant harvesting, which can be costly in the full scale wetland treatment setting and does not always yield an appreciable amount of nitrogen removal. Of the series with four tanks, the series loaded with 11.4 g TN/day removed an average of 54.9 percent of the applied TN; the 8.0 g TN/day series removed 60.8 percent of the applied TN; the series loaded with 2.3 g TN/day removed an average of 78.0 percent of the a TN applied; and the series loaded with 0.5 g TN/day removed an average of 33.4 percent of the applied TN. Additionally, the 2.3 g TN/day series with two tanks removed 44.0 percent of the applied TN, and the 2.3 g TN/day series with five tanks removed 82.8 percent of the applied TN. The wetland plants removed 14.9 percent of the applied TN in the 0.5 g TN/day series. This nitrogen removal in the biomass was the largest of all series tested. The smallest plant nitrogen removal percentage was observed in the 11.4 g TN/day series (4.87 percent). Additionally, a model of dry-weight biomass production with increasing TN loading is presented. The biomass yield as a function of TN loading rate was highly significant ( = 0.010) with an R2 = 0.978.