Industrial Water wastewater Treatment Waste Minimization Sludge Handling

Industrial Water & wastewater Treatment Waste Minimization & Sludge Handling

Introduction - Residuals is a term currently used to refer to “sludge” - The higher the degree of wastewater treatment, the larger the quantity of sludge to be treated and handled - In order to reduce the operating costs (approximately 50% of the plant costs) of wastewater treatment plants, the need for reducing the volume of sludge has become increasingly important. - Properly designed and efficiently operated sludge processing and disposal system is essential to the overall success of the wastewater treatment effort.

Sewage Sludge Bio-solids - The end product of wastewater sludge treatment processes is refered as “biosolids”. - It is a recyclable primarily organic solid material produced by wastewtaer treatment processes. - It is also a solid organic matter recovered from sewage treatment process and used especially as fertilizer for plants. - Its more reuse potential rather than the term “treated wastewater sludge”

Use and Disposal of Sewage Sludge Bio-solids used in many ways include: - Land application to agricultural land. - Land application to nonagricultural lands ( parks, highways, recreational areas, golf courses) Disposal methods of bio-solids include: - Disposal in municipal landfills - Disposal on delicate sites , surface disposal and incineration. Surface disposal includes piles of bio-solids left on the land surface and land application to dedicated nonagricultural land, and disposal in monofills. Monofills: a landfill intended for one type of waste only

Regulatory requirements Pathogen reduction requirements for land application of bio-solids are divided into two categories: Class A and Class B bio-solids. The six treatment alternatives for bio-solids include: - Alternative 1, thermally treated. - Alternative 2, high PH-high temperature treatment - Alternative 3, other processes treatment - Alternative 4, unknown processes - Alternative 5, use of the processes for further reduce pathogens (PFRP) and - Alternative 6, use of a process equivalent to PFRP

Regulatory requirements EXAMPLE 1 What is the required minimum time to achieve Class A pathogen requirement when a bio-solid with 15% solids content is heated at 60 o. C ?

Regulatory requirements EXAMPLE 2 Determine the required minimum temperature to treat bio-solid containing 15% solids with a heating time of 30 min.

Regulatory requirements Bio-solids Class B requirements ensure that pathogens have been reduced to levels that are unlikely to pose a threat to public health and environment under specific conditions of use. Class B bio-solids must meet one of the following alternatives: 1 - Monitoring of indicator organisms density. 2 - Bio-solids are treated in one of the processes to significantly reduce pathogens (PSRP). 3 - Use of the processes equivalent to PSRP.

Regulatory requirements Land application Bio-soilds applied to land either to condition the soil or to fertilize crops in the soil - Bio-soilds can apply to land in bulk or sold or in bags. - The application sites may be nonpublic contact sites 9 agricultural lands, forests, reclamation sites). Public contact sites (public parks, roadsides, lawns and home gardens). - All land application of bio-solids must meet the ceiling concentration limits for 10 heavy metals listed in the second column of below table. - Bio-solids applied to the land must meet pollutant concentration (PC limits , commutative pollutant loading rate (CPLR) limits

Regulatory requirements Annual Whole Sludge Application Rate AWSAR for bio-solids sold or given a way in a bag can be determined by dividing the annual pollutant loading rate by pollutant concentration.

Example 3 Ten heavy metals listed in previous table were analyzed in bio-solids to be sold. The chromium concentration is 20 mg/Kg of bio-solids. Determine the AWSAR of chromium for the bio-solids. .

Regulatory requirements Calculation of Annual Bio-solids Application rate on Agricultural Land Sewage sludge has been applied to agricultural land for long time. - The use of bio-solids in agricultural land can replace costly commercial fertilizers. - The annual application rates of biosolids should not exceed the nutrients (N and P) requirments of the crop grown on an agricultural soil. - calculations will be make are depends on : - 1 - Nitrogen - 2 - Phosphorus - 3 - pollutant limitation

Next Lecture Sludge treatment alternatives