I created the new column "validated" to my _customers table as tinyint(1)
in main/controllers/account/register.php inside the function private function _addCustomer() i added a new line as follows...

private function _addCustomer() {
		if ($this->validateForm() === TRUE) {
            $this->load->model('Customers_model');													// load the customers model
            $this->load->model('Customer_groups_model');

 			$add = array();

 			// if successful CREATE an array with the following $_POST data values
			$add['first_name'] 				= $this->input->post('first_name');
			$add['last_name'] 				= $this->input->post('last_name');
			$add['email'] 					= $this->input->post('email');
			$add['password'] 				= $this->input->post('password');
			$add['telephone'] 				= $this->input->post('telephone');
			$add['security_question_id']	= $this->input->post('security_question');
			$add['security_answer'] 		= $this->input->post('security_answer');
			$add['newsletter'] 				= $this->input->post('newsletter');
			$add['terms_condition'] 		= $this->input->post('terms_condition');
			$add['customer_group_id'] 		= $this->config->item('customer_group_id');
			$add['date_added'] 				= mdate('%Y-%m-%d', time());
			_$add['validated'] 				= '0'; //the table _customers has this column added as tinyint(1)_

			$result = $this->Customer_groups_model->getCustomerGroup($this->config->item('customer_group_id'));
			if ($result['approval'] === '1') {
				$add['status'] = '0';
			} else {
				$add['status'] = '1';
			}

Registration works fine but the column has null instead of the 0. Did I miss something or is there anywhere else I would need to add code for this to work?